CINXE.COM

<!DOCTYPE html> <html class='v2' dir='ltr' xmlns='http://www.w3.org/1999/xhtml' xmlns:b='http://www.google.com/2005/gml/b' xmlns:data='http://www.google.com/2005/gml/data' xmlns:expr='http://www.google.com/2005/gml/expr'> <head> <link href='https://www.blogger.com/static/v1/widgets/3566091532-css_bundle_v2.css' rel='stylesheet' type='text/css'/> <meta content='width=1100' name='viewport'/> <meta content='text/html; charset=UTF-8' http-equiv='Content-Type'/> <meta content='blogger' name='generator'/> <link href='http://www.righto.com/favicon.ico' rel='icon' type='image/x-icon'/> <link href='http://www.righto.com/2016/06/' rel='canonical'/> <link rel="alternate" type="application/atom+xml" title="Ken Shirriff's blog - Atom" href="http://www.righto.com/feeds/posts/default" /> <link rel="alternate" type="application/rss+xml" title="Ken Shirriff's blog - RSS" href="http://www.righto.com/feeds/posts/default?alt=rss" /> <link rel="service.post" type="application/atom+xml" title="Ken Shirriff's blog - Atom" href="https://www.blogger.com/feeds/6264947694886887540/posts/default" />  <meta content='http://www.righto.com/2016/06/' property='og:url'/> <meta content='Ken Shirriff's blog' property='og:title'/> <meta content='Computer history, restoring vintage computers, IC reverse engineering, and whatever' property='og:description'/> <title>Ken Shirriff's blog: June 2016</title> <style type='text/css'>@font-face{font-family:'Play';font-style:normal;font-weight:400;font-display:swap;src:url(//fonts.gstatic.com/s/play/v19/6aez4K2oVqwIvtU2Gw.eot);}</style> <style id='page-skin-1' type='text/css'></style> <style id='template-skin-1' type='text/css'></style> <meta content='width=device-width, initial-scale=1.0, maximum-scale=12.0, minimum-scale=.25, user-scalable=yes' name='viewport'/> <meta content='mw8ww70r3jW0GzXY6j1d' name='follow_it-verification-code'/> <link href='https://www.blogger.com/dyn-css/authorization.css?targetBlogID=6264947694886887540&zx=3c6b5127-1bf4-49a7-9645-31cfcd883d0b' media='none' onload='if(media!='all')media='all'' rel='stylesheet'/><noscript><link href='https://www.blogger.com/dyn-css/authorization.css?targetBlogID=6264947694886887540&zx=3c6b5127-1bf4-49a7-9645-31cfcd883d0b' rel='stylesheet'/></noscript> <meta name='google-adsense-platform-account' content='ca-host-pub-1556223355139109'/> <meta name='google-adsense-platform-domain' content='blogspot.com'/> </head> <body class='loading'> <div class='navbar no-items section' id='navbar'> </div> <div class='body-fauxcolumns'> <div class='fauxcolumn-outer body-fauxcolumn-outer'> <div class='cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left'> <div class='fauxborder-right'></div> <div class='fauxcolumn-inner'> </div> </div> <div class='cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div> </div> <div class='content'> <div class='content-fauxcolumns'> <div class='fauxcolumn-outer content-fauxcolumn-outer'> <div class='cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left'> <div class='fauxborder-right'></div> <div class='fauxcolumn-inner'> </div> </div> <div class='cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div> </div> <div class='content-outer'> <div class='content-cap-top cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left content-fauxborder-left'> <div class='fauxborder-right content-fauxborder-right'></div> <div class='content-inner'> <header> <div class='header-outer'> <div class='header-cap-top cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left header-fauxborder-left'> <div class='fauxborder-right header-fauxborder-right'></div> <div class='region-inner header-inner'> <div class='header section' id='header'><div class='widget Header' data-version='1' id='Header1'> <div id='header-inner' style='background-image: url("https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-4KXwYe0lQ4HFzhAye9vvRlij2ZYvMbfPCnqEE__1o85Fjo3XgefxJQhWRdwR3EzNWNMWT3yMaj2QZaT9GazqQx3C6oWa3-hBNlRHG7f-Oib-lv1Wq_C2_A0rt8xZgs87iNqzRVKK7H0A/s800/background.jpg"); background-position: left; width: 550px; min-height: 105px; _height: 105px; background-repeat: no-repeat; '> <div class='titlewrapper' style='background: transparent'> <h1 class='title' style='background: transparent; border-width: 0px'> <a href='http://www.righto.com/'> Ken Shirriff's blog </a> </h1> </div> <div class='descriptionwrapper'> <p class='description'><span>Computer history, restoring vintage computers, IC reverse engineering, and whatever</span></p> </div> </div> </div></div> </div> </div> <div class='header-cap-bottom cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div> </header> <div class='tabs-outer'> <div class='tabs-cap-top cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left tabs-fauxborder-left'> <div class='fauxborder-right tabs-fauxborder-right'></div> <div class='region-inner tabs-inner'> <div class='tabs no-items section' id='crosscol'></div> <div class='tabs no-items section' id='crosscol-overflow'></div> </div> </div> <div class='tabs-cap-bottom cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div> <div class='main-outer'> <div class='main-cap-top cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left main-fauxborder-left'> <div class='fauxborder-right main-fauxborder-right'></div> <div class='region-inner main-inner'> <div class='columns fauxcolumns'> <div class='fauxcolumn-outer fauxcolumn-center-outer'> <div class='cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left'> <div class='fauxborder-right'></div> <div class='fauxcolumn-inner'> </div> </div> <div class='cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div> <div class='fauxcolumn-outer fauxcolumn-left-outer'> <div class='cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left'> <div class='fauxborder-right'></div> <div class='fauxcolumn-inner'> </div> </div> <div class='cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div> <div class='fauxcolumn-outer fauxcolumn-right-outer'> <div class='cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left'> <div class='fauxborder-right'></div> <div class='fauxcolumn-inner'> </div> </div> <div class='cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div>  <div class='columns-inner'> <div class='column-center-outer'> <div class='column-center-inner'> <div class='main section' id='main'><div class='widget Blog' data-version='1' id='Blog1'> <div class='blog-posts hfeed'> <div class="date-outer"> <div class="date-posts"> <div class='post-outer'> <div class='post hentry' itemprop='blogPost' itemscope='itemscope' itemtype='http://schema.org/BlogPosting'> <meta content='//static.righto.com/images/alto/alto-w200.jpg' itemprop='image_url'/> <meta content='6264947694886887540' itemprop='blogId'/> <meta content='2474206492273229975' itemprop='postId'/> <a name='2474206492273229975'></a> <h3 class='post-title entry-title' itemprop='name'> <a href='http://www.righto.com/2016/06/hello-world-in-bcpl-language-on-xerox.html'>"Hello world" in the BCPL language on the Xerox Alto simulator</a> </h3> <div class='post-header'> <div class='post-header-line-1'></div> </div> <div class='post-body entry-content' id='post-body-2474206492273229975' itemprop='description articleBody'> <style> code {font-size: 100%; font-family: courier, fixed;} pre.bcpl {font-family: courier, fixed; padding: 10px; background-color: #eee;line-height: 100%} </style> <meta property="og:image" content="//static.righto.com/images/alto/alto_pullout-s640.jpg" /> <p> The first programming language for the Xerox Alto was BCPL, the language that led to C. This article shows how to write a BCPL "Hello World" program using <i>Bravo</i>, the first WYSIWYG text editor, and run it on the Alto simulator. <p> The Xerox Alto is the legendary minicomputer from 1973 that helped set the direction for personal computing. Since I'm helping restore a Xerox Alto (<a href="http://www.righto.com/2016/06/y-combinators-xerox-alto-restoring.html">details</a>), I wanted to learn more about BCPL programming. (The influential Mesa and and Smalltalk languages were developed on the Alto, but those are a topic for another post.) <p> <a href="//static.righto.com/images/alto/alto.jpg"><img alt="The Xerox Alto II XM computer. Note the video screen is arranged in portrait mode. Next to the keyboard is a mouse. The Diablo disk drive is below the keyboard. The base contains the circuit boards and power supplies." class="hilite" height="343" src="//static.righto.com/images/alto/alto-w200.jpg" title="The Xerox Alto II XM computer. Note the video screen is arranged in portrait mode. Next to the keyboard is a mouse. The Diablo disk drive is below the keyboard. The base contains the circuit boards and power supplies." width="200"> </a> <p> <div class="cite"> The Xerox Alto II XM computer. Note the video screen is arranged in portrait mode. Next to the keyboard is a mouse. The Diablo disk drive is below the keyboard. The base contains the circuit boards and power supplies. </div> <p> <h2>Using the simulator</h2> Since the Alto I'm restoring isn't running yet, I ran my BCPL program on <i>Salto</i>, an Alto simulator for Linux written by Juergen Buchmueller. To build it, download the simulator source from <a href="https://github.com/brainsqueezer/salto_simulator">github.com/brainsqueezer/salto_simulator</a>, install the dependencies listed in the README, and run <code>make</code>. Then run the simulator with the appropriate Alto disk image: <pre class="bcpl"> bin/salto disks/tdisk4.dsk.Z </pre> <p> Here's what the simulator looks like when it's running: <p> <a href="//static.righto.com/images/alto/screenshot_startup.png"><img alt="The Salto simulator for the Xerox Alto." class="hilite" height="412" src="//static.righto.com/images/alto/screenshot_startup-w600.png" title="The Salto simulator for the Xerox Alto." width="600"> </a> <p> <div class="cite"> The Salto simulator for the Xerox Alto. </div> <p> (To keep this focused, I'm not going to describe everything you can run on the simulator, but I'll point out that pressing <code>?</code> at the command line will show the directory contents. Anything ending in <code>.run</code> is a program you can run, e.g. "pinball".) <p> Type <code>bravo</code> to start the Bravo text editor. Press <code>i</code> (for insert). Enter the BCPL program: <pre class="bcpl"> // Hello world demo get "streams.d" external [ Ws ] let Main() be [ Ws("Hello World!*N") ] </pre> Here's a screenshot of the Bravo editor with the program entered: <p> <a href="//static.righto.com/images/alto/bravo.png"><img alt="A Xerox Alto 'Hello World' program for written in BCPL, in the Bravo editor." class="hilite" height="300" src="//static.righto.com/images/alto/bravo-w600.png" title="A Xerox Alto 'Hello World' program for written in BCPL, in the Bravo editor." width="600"> </a> <p> <div class="cite"> A Xerox Alto 'Hello World' program for written in BCPL, in the Bravo editor. </div> <br>Press <code>ESC</code> to exit insert mode. <br>Press <code>p</code> (put) to save the file. <br>Type <code>hello.bcpl</code> (the file name) and press <code>ESC</code> (not enter!). <br>Press <code>q</code> then <code>ENTER</code> to quit the editor. <p> Run the BCPL compiler, the linker, and the executable by entering the following commands at the prompt: <pre class="bcpl"> bcpl hello.bcpl bldr/d/l/v hello hello </pre> If all goes well, the program will print "Hello World!" Congratulations, you've run a BCPL program. <p> <a href="//static.righto.com/images/alto/hello.png"><img alt="Output of the Hello World program in BCPL on the Xerox Alto simulator." class="hilite" height="62" src="//static.righto.com/images/alto/hello-w300.png" title="Output of the Hello World program in BCPL on the Xerox Alto simulator." width="300"> </a> <p> <div class="cite"> Output of the Hello World program in BCPL on the Xerox Alto simulator. </div> <p> The following figure explains the Hello World program. If you know C, the program should be comprehensible. <p> <a href="//static.righto.com/images/alto/commented_code.png"><img alt="'Hello World' program in BCPL with explanation." class="hilite" height="271" src="//static.righto.com/images/alto/commented_code-w450.png" title="'Hello World' program in BCPL with explanation." width="450"> </a> <p> <div class="cite"> 'Hello World' program in BCPL with explanation. </div> <h2>The BCPL language</h2> The BCPL language is interesting because it was the grandparent of C. <a href="https://en.wikipedia.org/wiki/BCPL">BCPL</a> (Basic Combined Programming Language) was developed in 1966. The B language was <a href="https://www.bell-labs.com/usr/dmr/www/chist.html">developed</a> in 1969 as a stripped down version of BCPL by Ken Thompson and Dennis Ritchie. With the introduction of the PDP-11, system software needed multiple datatypes, resulting in the development of the C language around 1972. <p> Overall, BCPL is like a primitive version of C with weirdly different syntax. The only type that BCPL supports is the 16-bit word, so it doesn't use type declarations. BCPL does support supports C-like structs and unions, including structs that can access bit fields from a word. (This is very useful for the low-level systems programming tasks that BCPL was designed for.) BCPL also has blocks and scoping rules like C, pointers along with lvalues and rvalues, and C-like looping constructs. <p> A BCPL program looks strange to a C programmer because many of the special characters are different and BCPL often uses words instead of special characters. Here are some differences: <p> Blocks are defined with <code>[...]</code> rather than <code>{...}</code>. <br>For array indexing, BCPL uses <code>a!b</code> instead of <code>a[b]</code>. <br>BCPL uses <code>resultis 42</code> instead of <code>return 42</code>. <br>Semicolons are optional, kind of like JavaScript. <br>For pointers, BCPL uses <code>lv</code> and <code>rv</code> (lvalue and rvalue) instead of <code>&</code> and <code>*</code>. rvalues. <br>The BCPL operator <code>=></code> (known as "heffalump"; I'm not making this up) is used for indirect structure references instead of C's <code>-></code>. <br><code>selecton X into</code>, instead of C's <code>switch</code>, but cases are very similar with fall-throughs and default. <br><code>lshift</code> and <code>rshift</code> instead of <code><<</code> and <code>>></code>. <br><code>eq</code>, <code>ne</code>, <code>ls</code>, <code>le</code>, <code>gr</code>, <code>ge</code> in place of <code>==</code>, <code>!=</code>, <code><</code>, <code><=</code>, <code>></code>, <code>>=</code>. <br><code>test / ifso / ifnot</code> instead of <code>if / else</code>. <p> A BCPL reference manual is <a href="http://bitsavers.org/pdf/xerox/alto/bcpl/AltoBCPLdoc.pdf">here</a> if you want all the details of BCPL. <h2>More about the Bravo editor</h2> The Bravo editor was the first editor with WYSIWYG (what you see is what you get) editing. You could format text on the screen and print the text on a laser printer. Bravo was written by Butler Lampson and Charles Simonyi in 1974. Simonyi later moved to Microsoft, where he wrote Word, based on the ideas in Bravo. <p> Steve Jobs saw the Alto when he famously toured Xerox Parc in 1979, and it inspired the GUI for the Lisa and Mac. However, Steve Jobs <a href="http://news.stanford.edu/2005/06/14/jobs-061505/">said in a commencement address</a>, "[The Mac] was the first computer with beautiful typography. If I had never dropped in on that [calligraphy] course in college, the Mac would have never had multiple typefaces or proportionally spaced fonts. And since Windows just copied the Mac, it's likely that no personal computer would have them." This is absurd since the Alto had a variety of high-quality proportionally spaced fonts in 1974, before the Apple I was created, let alone the Macintosh. <p> The image below shows the Hello World program with multiple fonts and centering applied. Since the compiler ignores any formatting, the program runs as before. (Obviously styling is more useful for documents than code.) <p> <a href="//static.righto.com/images/alto/formatted.png"><img alt="The Bravo editor provides WYSIWYG formatting of text." class="hilite" height="314" src="//static.righto.com/images/alto/formatted-w600.png" title="The Bravo editor provides WYSIWYG formatting of text." width="600"> </a> <p> <div class="cite"> The Bravo editor provides WYSIWYG formatting of text. </div> <p> The manual for Bravo is <a href="http://bitsavers.trailing-edge.com/pdf/xerox/alto/BravoCourse.pdf">here</a> but I'll give a quick guide to Bravo if you want to try more editing. Bravo is a mouse-based editor, so use the mouse to select the text for editing. left click and right click under text to select it with an underline. The editor displays the current command at the top of the editing window. If you mistype a command, pressing <code>DEL</code> (delete) will usually get you out of it. Pressing <code>u</code> provides an undo. <p> To delete selected text, press <code>d</code>. To insert more text, press <code>i</code>, enter the text, then <code>ESC</code> to exit insert mode. To edit an existing file, start Bravo from the command line, press <code>g</code> (for get), then enter the filename and press <code>ESC</code>. To apply formatting, select characters, press <code>l</code> (look), and then enter a formatting code (0-9 to change font, b for bold, i for italics). <h2>Troubleshooting</h2> If your program has an error, compilation will fail with an error message. The messages don't make much sense, so try to avoid typos. <p> The simulator has a few bugs and tends to start failing after a few minutes with errors in the simulated disk. This will drop you into the Alto debugger, called <i>Swat</i>. At that point, you should restart the simulator. Unfortunately any files you created in the simulator will be lost when you exit the simulator. <p> <a href="//static.righto.com/images/alto/swat.png"><img alt="If something goes wrong, you'll end up in Swat, the Xerox Alto's debugging system." class="hilite" height="292" src="//static.righto.com/images/alto/swat-w600.png" title="If something goes wrong, you'll end up in Swat, the Xerox Alto's debugging system." width="600"> </a> <p> <div class="cite"> If something goes wrong, you'll end up in Swat, the Xerox Alto's debugging system. </div> <h2>Conclusion</h2> The BCPL language (which predates the Alto) had a huge influence on programming languages since it led to C (and thus C++, Java, C#, and so forth). The Bravo editor was the first WYSIWYG text editor and strongly influenced personal computer word processing. Using the Alto simulator, you can try both BCPL and Bravo for yourself by compiling a "Hello World" program, and experience a slice of 1970s computing history. <div style='clear: both;'></div> </div> <div class='post-footer'> <div class='post-footer-line post-footer-line-1'><span class='post-comment-link'> <a class='comment-link' href='https://www.blogger.com/comment/fullpage/post/6264947694886887540/2474206492273229975' onclick=''> 10 comments: </a> </span> <span class='post-icons'> <span class='item-action'> <a href='https://www.blogger.com/email-post/6264947694886887540/2474206492273229975' title='Email Post'> <img alt='' class='icon-action' height='13' src='http://img1.blogblog.com/img/icon18_email.gif' width='18'/> </a> </span> <span class='item-control blog-admin pid-1138732533'> <a href='https://www.blogger.com/post-edit.g?blogID=6264947694886887540&postID=2474206492273229975&from=pencil' title='Edit Post'> <img alt='' class='icon-action' height='18' src='https://resources.blogblog.com/img/icon18_edit_allbkg.gif' width='18'/> </a> </span> </span> <span class='post-backlinks post-comment-link'> </span> <div class='post-share-buttons goog-inline-block'> <a class='goog-inline-block share-button sb-email' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=2474206492273229975&target=email' target='_blank' title='Email This'><span class='share-button-link-text'>Email This</span></a><a class='goog-inline-block share-button sb-blog' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=2474206492273229975&target=blog' onclick='window.open(this.href, "_blank", "height=270,width=475"); return false;' target='_blank' title='BlogThis!'><span class='share-button-link-text'>BlogThis!</span></a><a class='goog-inline-block share-button sb-twitter' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=2474206492273229975&target=twitter' target='_blank' title='Share to X'><span class='share-button-link-text'>Share to X</span></a><a class='goog-inline-block share-button sb-facebook' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=2474206492273229975&target=facebook' onclick='window.open(this.href, "_blank", "height=430,width=640"); return false;' target='_blank' title='Share to Facebook'><span class='share-button-link-text'>Share to Facebook</span></a><a class='goog-inline-block share-button sb-pinterest' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=2474206492273229975&target=pinterest' target='_blank' title='Share to Pinterest'><span class='share-button-link-text'>Share to Pinterest</span></a> </div> </div> <div class='post-footer-line post-footer-line-2'><span class='post-labels'> Labels: <a href='http://www.righto.com/search/label/alto' rel='tag'>alto</a> </span> </div> <div class='post-footer-line post-footer-line-3'></div> </div> </div> </div> </div></div> <div class="date-outer"> <div class="date-posts"> <div class='post-outer'> <div class='post hentry' itemprop='blogPost' itemscope='itemscope' itemtype='http://schema.org/BlogPosting'> <meta content='//static.righto.com/images/baytobreakers/27004787176_639a3fe794_z-w600.jpg' itemprop='image_url'/> <meta content='6264947694886887540' itemprop='blogId'/> <meta content='5972120097560087019' itemprop='postId'/> <a name='5972120097560087019'></a> <h3 class='post-title entry-title' itemprop='name'> <a href='http://www.righto.com/2016/06/inside-tiny-rfid-chip-that-runs-san.html'>Inside the tiny RFID chip that runs San Francisco's "Bay to Breakers" race</a> </h3> <div class='post-header'> <div class='post-header-line-1'></div> </div> <div class='post-body entry-content' id='post-body-5972120097560087019' itemprop='description articleBody'> <meta property="og:image" content="//static.righto.com/images/baytobreakers/chip_0014-s640.png" /> <p> How does a tiny chip time the runners in the Bay to Breakers race? In this article, I take die photos of the RFID chip used to track athletes during the race. <p> <a href="//static.righto.com/images/baytobreakers/27004787176_639a3fe794_z.jpg"><img alt="Bay to Breakers, 2016. Photo courtesy of David Yu, CC BY-NC-ND 2.0." class="hilite" height="399" src="//static.righto.com/images/baytobreakers/27004787176_639a3fe794_z-w600.jpg" title="Bay to Breakers, 2016. Photo courtesy of David Yu, CC BY-NC-ND 2.0." width="600"> </a> <p> <div class="cite"> Bay to Breakers, 2016. Photo courtesy of <a href="https://www.flickr.com/photos/davidyuweb/27004787176/in/photostream/">David Yu</a>, <a href="https://creativecommons.org/licenses/by-nc-nd/2.0/">CC BY-NC-ND 2.0</a>. </div> <p> Bay to Breakers is the iconic San Francisco race, with tens of thousands of runners (many in costume and some in nothing) running 12km across the city. To determine their race time, each runner wears an identification bib. As you can see below, the back of the bib has a small foam rectangle with a metal foil antenna and a tiny chip underneath. The runners are tracked using a technology called RFID (<a href="https://en.wikipedia.org/wiki/Radio-frequency_identification">Radio Frequency Identification</a>). <p> <a href="//static.righto.com/images/baytobreakers/bib.jpg"><img alt="The bib worn by runners in the Bay to Breakers race. At the top, behind the foam is an antenna and RFID chip used to detect the runner at the start and end of the race." class="hilite" height="300" src="//static.righto.com/images/baytobreakers/bib-w600.jpg" title="The bib worn by runners in the Bay to Breakers race. At the top, behind the foam is an antenna and RFID chip used to detect the runner at the start and end of the race." width="600"> </a> <p> <div class="cite"> The bib worn by runners in the Bay to Breakers race. At the top, behind the foam is an antenna and RFID chip used to detect the runner at the start and end of the race. </div> <p> At the beginning and end of the race, the runners cross special mats that contain antennas and broadcast ultra high frequency radio signals. The runner's RFID chip detects this signal and sends back the athlete's ID number, which is programmed into the chip. By tracking these ID numbers, the system determines the time each runner took to run the race. The cool thing about these RFID chips is they are powered by the received radio signal; they don't need a battery. <p> <a href="http://www.mylaps.com/en/system-components/bibtag-system">Mylaps</a>, whose name appears on the foam rectangle, is a company that supplies sports timing systems: the bibs with embedded RFID chips, the detection mats, and portable detection hardware. The detection system is designed to handle large numbers of runners, scanning more than 50 tags per second. <p> Removing the foam reveals an unusually-shaped metal antenna, the tiny RFID chip (the black dot above the word "DO", and the barely-visible word "Smartrac". Studying the <a href="https://www.smartrac-group.com/files/content/Products_Services/PDF/DogBone_M4.pdf">Smartrac</a> website reveals that this chip is the <a href="https://support.impinj.com/hc/en-us/articles/202756908-Monza-4-RFID-Tag-Chip-Datasheet">Impinj Monza 4</a> RFID chip, which operates in the 860-960 MHz frequency range and is recommended for sports timing. <p> <a href="//static.righto.com/images/baytobreakers/antenna.jpg"><img alt="The RFID circuit used to detect runners in the Bay to Breakers. The metal forms an antenna. The tiny black square in the center is the RFID chip." class="hilite" height="165" src="//static.righto.com/images/baytobreakers/antenna-w600.jpg" title="The RFID circuit used to detect runners in the Bay to Breakers. The metal forms an antenna. The tiny black square in the center is the RFID chip." width="600"> </a> <p> <div class="cite"> The RFID circuit used to detect runners in the Bay to Breakers. The metal forms an antenna. The tiny black square in the center is the RFID chip. </div> <p> Getting the chip off the bib was a bit tricky. I softened the bib material in <a href="http://amzn.to/28QsRzc">Goof Off</a>, dissolved the aluminum antenna metal with HCl and removed the adhesive with a mysterious BGA adhesive solvent I ordered from Shenzhen. <p> The chip itself is remarkably tiny, about the size of a grain of salt. The picture below shows the chip on a penny, as seen through a microscope: for scale, a grain of salt is by the <i>R</i> and the chip is on the <i>U</i> (in <i>TRUST</i>). This is regular salt, by the way, not coarse sea salt or kosher salt. I spent a lot of time trying to find the chip when it fell on my desk, since it is practically a speck. <p> <a href="//static.righto.com/images/baytobreakers/chip_0008.png"><img alt="The RFID chip used to identify runners is very small, about the size of one of the letters on a penny. A grain of salt (next to R) and the RFID chip (next to U)." class="hilite" height="460" src="//static.righto.com/images/baytobreakers/chip_0008-w600.png" title="The RFID chip used to identify runners is very small, about the size of one of the letters on a penny. A grain of salt (next to R) and the RFID chip (next to U)." width="600"> </a> <p> <div class="cite"> The RFID chip used to identify runners is very small, about the size of one of the letters on a penny. A grain of salt (next to R) and the RFID chip (next to U). </div> <p> In the picture above, you can see the four round contact points where the chip was connected to the antenna. There's still a blob of epoxy or something around the die, making it hard to see the details. The chip decapsulation gurus use use boiling nitric and sulfuric acids to remove epoxy, but I'm not that hardcore so I heated the chip over a stove flame. This burned off the epoxy much better than I expected, making the die clearly visible as you can see in the next photo. <p> I took 34 die photos using my metallurgical microscope and stitched them together to get a hi-res photo. (I described the stitching process in detail <a href="http://www.righto.com/2015/12/creating-high-resolution-integrated.html">here</a>). The result is the die photo below (click it for the large image). Surprisingly, there is no identifying name or number on the chip. However, comparing my die photo with the picture in the <a href="https://support.impinj.com/hc/en-us/articles/202756908-Monza-4-RFID-Tag-Chip-Datasheet">datasheet</a> confirms that the chip is the Monza 4 RFID chip. <p> I can identify some of the chip's layout, but the chip is too dense and has too many layers for me to reverse engineer the exact details. Thus, the description that follows is slightly speculative. <p> <a href="//static.righto.com/images/baytobreakers/stitched.jpg"><img alt="Die photo of the Impinj Monza 4 RFID chip." class="hilite" height="707" src="//static.righto.com/images/baytobreakers/stitched-w700.jpg" title="Die photo of the Impinj Monza 4 RFID chip." width="700"> </a> <p> <div class="cite"> Die photo of the Impinj Monza 4 RFID chip. </div> <p> The four pins in the corners are where the antenna is connected. (The chip has four pins because two antennas can be used for improved detection.) <p> The left part of the chip is the analog logic, extracting power from the antenna, reading the transmitted signal, and modulating the return signal. The rectangles on the left are probably transistors and capacitors forming a charge pump to extract power from the radio signal (see <a href="https://www.google.com/patents/US7561866">patent 7,561,866</a>). <p> The right third of the chip is so-called "random logic" that carries out the commands sent to the chip. According to the datasheet, the chip uses a digital logic finite state machine, so the chip probably doesn't have a full processor. <p> The 32 orderly stripes in the middle are the non-volatile memory (NVM). Above the stripes, the address decode circuitry is barely visible. The chip has 928 bits of storage (counting up the memory banks on the datasheet) so I suspect the memory is set up as a 32x29 array. Some NVM details are in <a href="https://www.google.com/patents/US7307534">patent 7307534</a>. <p> Along the lower and right edges of the chip, red lines are visible; these connect chips together on the wafer for testing during manufacturing (<a href="https://www.google.com/patents/US7307528">patent 7307528</a>). <p> <a href="//static.righto.com/images/baytobreakers/chip_0014.png"><img alt="The Impinj Monza 4 RFID chip on top of a 8751 microcontroller chip shows that the RFID chip is very small and dense." class="hilite" height="460" src="//static.righto.com/images/baytobreakers/chip_0014-w600.png" title="The Impinj Monza 4 RFID chip on top of a 8751 microcontroller chip shows that the RFID chip is very small and dense." width="600"> </a> <p> <div class="cite"> The Impinj Monza 4 RFID chip on top of a 8751 microcontroller chip shows that the RFID chip is very small and dense. </div> <p> To show how small the chip is, and how technology has changed, I put the RFID chip on top of an 8751 microcontroller die. The 8751 microcontroller is a chip in Intel's popular <a href="https://en.wikipedia.org/wiki/Intel_MCS-51">8051 family</a> dating from 1983. Note that the circuitry on the RFID chip is denser and the chip is much, much smaller. (The photo looks a bit photoshopped, but it genuinely is the RFID chip sitting on the surface of the 8751 die. I don't know why the RFID chip is pink.) <p> So, if you ran in the Bay to Breakers, that's the chip that tracked your time during the race. (There aren't a lot of other RFID die photos on the web, but a few are at <a href="http://www.bunniestudios.com/blog/?p=1379">Bunnie Studios</a>, <a href="http://zeptobars.com/en/read/mifare-rfid-metro-mikron-sitronics">Zeptobars</a> and <a href="http://www.extremetech.com/extreme/141077-how-to-crack-open-some-computer-chips-and-take-your-own-die-shots">ExtremeTech</a> if you want to see more.) <div style='clear: both;'></div> </div> <div class='post-footer'> <div class='post-footer-line post-footer-line-1'><span class='post-comment-link'> <a class='comment-link' href='https://www.blogger.com/comment/fullpage/post/6264947694886887540/5972120097560087019' onclick=''> 3 comments: </a> </span> <span class='post-icons'> <span class='item-action'> <a href='https://www.blogger.com/email-post/6264947694886887540/5972120097560087019' title='Email Post'> <img alt='' class='icon-action' height='13' src='http://img1.blogblog.com/img/icon18_email.gif' width='18'/> </a> </span> <span class='item-control blog-admin pid-1138732533'> <a href='https://www.blogger.com/post-edit.g?blogID=6264947694886887540&postID=5972120097560087019&from=pencil' title='Edit Post'> <img alt='' class='icon-action' height='18' src='https://resources.blogblog.com/img/icon18_edit_allbkg.gif' width='18'/> </a> </span> </span> <span class='post-backlinks post-comment-link'> </span> <div class='post-share-buttons goog-inline-block'> <a class='goog-inline-block share-button sb-email' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=5972120097560087019&target=email' target='_blank' title='Email This'><span class='share-button-link-text'>Email This</span></a><a class='goog-inline-block share-button sb-blog' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=5972120097560087019&target=blog' onclick='window.open(this.href, "_blank", "height=270,width=475"); return false;' target='_blank' title='BlogThis!'><span class='share-button-link-text'>BlogThis!</span></a><a class='goog-inline-block share-button sb-twitter' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=5972120097560087019&target=twitter' target='_blank' title='Share to X'><span class='share-button-link-text'>Share to X</span></a><a class='goog-inline-block share-button sb-facebook' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=5972120097560087019&target=facebook' onclick='window.open(this.href, "_blank", "height=430,width=640"); return false;' target='_blank' title='Share to Facebook'><span class='share-button-link-text'>Share to Facebook</span></a><a class='goog-inline-block share-button sb-pinterest' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=5972120097560087019&target=pinterest' target='_blank' title='Share to Pinterest'><span class='share-button-link-text'>Share to Pinterest</span></a> </div> </div> <div class='post-footer-line post-footer-line-2'><span class='post-labels'> Labels: <a href='http://www.righto.com/search/label/chips' rel='tag'>chips</a>, <a href='http://www.righto.com/search/label/electronics' rel='tag'>electronics</a>, <a href='http://www.righto.com/search/label/reverse-engineering' rel='tag'>reverse-engineering</a> </span> </div> <div class='post-footer-line post-footer-line-3'></div> </div> </div> </div> </div></div> <div class="date-outer"> <div class="date-posts"> <div class='post-outer'> <div class='post hentry' itemprop='blogPost' itemscope='itemscope' itemtype='http://schema.org/BlogPosting'> <meta content='https://i.ytimg.com/vi/xPyqQXFC2yw/hqdefault.jpg' itemprop='image_url'/> <meta content='6264947694886887540' itemprop='blogId'/> <meta content='8792262437996446798' itemprop='postId'/> <a name='8792262437996446798'></a> <h3 class='post-title entry-title' itemprop='name'> <a href='http://www.righto.com/2016/06/restoring-y-combinators-xerox-alto-day.html'>Restoring Y Combinator's Xerox Alto, day 1: Power supplies and disk interface</a> </h3> <div class='post-header'> <div class='post-header-line-1'></div> </div> <div class='post-body entry-content' id='post-body-8792262437996446798' itemprop='description articleBody'> <meta property="og:image" content="//static.righto.com/images/alto/powersupply_opened-s800.jpg" /> <p> A few days ago, I wrote about how <a href="http://www.righto.com/2016/06/y-combinators-xerox-alto-restoring.html">I'm helping restore a Xerox Alto</a> for Y Combinator. This new post describes the first day of restoration: how we disassembled the computer and disk drive and fixed a power supply problem, but ran into a showstopper problem with the disk interface. <p> The Xerox Alto was a revolutionary computer from 1973, designed by computer pioneer <a href="https://en.wikipedia.org/wiki/Charles_P._Thacker">Chuck Thacker</a> at Xerox PARC to investigate ideas for personal computing. The Alto was the first computer built around a mouse and GUI, as well as introducing Ethernet and laser printers to the world. The Alto famously inspired Steve Jobs, who used many of its ideas in the Lisa and Macintosh computer. <p> Alan Kay, whose vision for a <a href="http://history-computer.com/Library/Kay72.pdf">personal computer</a> guided the Alto, recently gave an Alto computer to Y Combinator. Getting this system running again is a big effort but fortunately I'm working with a strong team, largely from the <a href="http://ibm-1401.info/">IBM 1401 restoration team</a>. Marc Verdiell, Luca Severini, Ron, Carl Claunch, and I started on restoration a few days ago, as shown in Marc's video below. <p> <iframe width="560" height="315" src="https://www.youtube.com/embed/xPyqQXFC2yw?rel=0" frameborder="0" allowfullscreen></iframe> <h2>Disassembling the Alto</h2> We started by disassembling the computer. The Xerox Alto has a metal cabinet about the size of a dorm mini-fridge, with a Diablo hard disk drive on top, and a chassis with power supplies and the circuit boards below. With some tugging, the chassis slides out of the cabinet on rails as you can see in the photo below. At the front are the four cooling fans, normally protected by a decorative panel. Note the unusual portrait layout of the display. <p> <a href="//static.righto.com/images/alto/alto_pullout.jpg"><img alt="The Xerox Alto II XM 'personal computer'. The card cage below the disk drive has been partially removed. Four cooling fans are visible at the front of it." class="hilite" height="555" src="//static.righto.com/images/alto/alto_pullout-w350.jpg" title="The Xerox Alto II XM 'personal computer'. The card cage below the disk drive has been partially removed. Four cooling fans are visible at the front of it." width="350"> </a> <p> <div class="cite"> The Xerox Alto II XM 'personal computer'. The card cage below the disk drive has been partially removed. Four cooling fans are visible at the front of it. </div> <p> With the chassis fully removed, you can see the four switching power supplies on the left, the blue metal boxes. The computer's circuit boards are on the right, not visible in this picture. The wiring for the backplane is visible at right front, with pins connected by wire-wrapped wire connections. This wiring connects the circuit boards together.<a class="ref" href="#ref1">[1]</a> <p> <a href="//static.righto.com/images/alto/orbit_backplane.jpg"><img alt="The Alto's chassis has been removed. On the left are the four switching power supplies (blue boxes). On the right, the connections for the wire-wrapped backplane are visible. The circuit boards plug into this backplane." class="hilite" height="424" src="//static.righto.com/images/alto/orbit_backplane-w600.jpg" title="The Alto's chassis has been removed. On the left are the four switching power supplies (blue boxes). On the right, the connections for the wire-wrapped backplane are visible. The circuit boards plug into this backplane." width="600"> </a> <p> <div class="cite"> The Alto's chassis has been removed. On the left are the four switching power supplies (blue boxes). On the right, the connections for the wire-wrapped backplane are visible. The circuit boards plug into this backplane. </div> <h2>The power supplies</h2> Our first goal was to make sure the power supplies worked after decades of sitting idle. The Alto uses high-efficiency switching power supplies.<a class="ref" href="#ref2">[2]</a> To explain the power supplies in brief, input power is chopped up thousands of times a second to produce a regulated voltage. Unlike modern computer power supplies, there's a second switching stage (the inverter), which drops the voltage to the desired 15 volts. This was more complexity than I expected, but fortunately the <a href="http://bitsavers.org/pdf/sorensen/Sorensen_SSD_Series_III_IIIA_Nov77.pdf">detailed power supply manual</a> was available online, thanks to Al Kossow's <a href="http://bitsavers.org">bitsavers</a>.<a class="ref" href="#ref3">[3]</a> We tested each power supply with a resistor as a dummy load and checked that the output voltage was correct. We also used an oscilloscope to make sure the output was stable. All the power supplies worked fine, except for the +15V supply (top center), which had trouble getting up to 15 volts and staying there. <p> We disassembled the faulty power supply to track down the problem. The photo of the power supply below shows how densely components are crammed into the power supply. Two of the circuit boards have been removed and are at the back. Note the three large filter capacitors at the front. <p> <a href="//static.righto.com/images/alto/powersupply_opened.jpg"><img alt="Switching power supply from the Xerox Alto computer. Two of the control boards have been removed and are visible at back." class="hilite" height="417" src="//static.righto.com/images/alto/powersupply_opened-w600.jpg" title="Switching power supply from the Xerox Alto computer. Two of the control boards have been removed and are visible at back." width="600"> </a> <p> <div class="cite"> Switching power supply from the Xerox Alto computer. Two of the control boards have been removed and are visible at back. </div> <p> We noted signs of overheating on the AC connector, as well as a somewhat sketchy looking repair (a trace replaced by a wire) and some signs of corrosion. Apparently the power supply had problems in the past and had been serviced. We cleaned up the corrosion and it appeared to be superficial. <p> The power supply disassembled easily for repair, as you can see below. The main board is at the right. The tower of three inductors on the main board is an unusual way of mounting inductors. Three circuit boards (top) plug into the main board. Because the power supply uses discrete components instead of a modern SMPS control IC, it needs a lot of control circuitry. The switching transistors (lower center) are mounted onto metal heat sinks for cooling. <p> <a href="//static.righto.com/images/alto/powersupply_disassembled.jpg"><img alt="The Alto's switching power supply, disassembled. The main board is in the lower right. The three circuit boards are at top, below the large input capacitors." class="hilite" height="539" src="//static.righto.com/images/alto/powersupply_disassembled-w600.jpg" title="The Alto's switching power supply, disassembled. The main board is in the lower right. The three circuit boards are at top, below the large input capacitors." width="600"> </a> <p> <div class="cite"> The Alto's switching power supply, disassembled. The main board is in the lower right. The three circuit boards are at top, below the large input capacitors. </div> <p> The large capacitors were attached with screws, making it easy to remove them for testing. A capacitance meter showed that the three large capacitors had failed, explaining why the power supply had trouble outputting the desired voltage. Ron went off and found replacement capacitors, although they weren't an exact match for the originals. With the new capacitors mounted in place, the power supply worked properly. <h2>Inside the Diablo disk drive</h2> We also looked at the Diablo disk drive, which provides 2.5MB of storage for the Xerox Alto. The first step was removing the disk pack. In normal operation, the front of the drive is locked shut to keep the disk from being removed during use. To remove the disk without powering up the drive, we had to open the drive and manually trip the latch that locks it shut (see <a href="http://bitsavers.org/pdf/diablo/81503-3_Diablo30Maint_Jul78.pdf">Diablo drive manual</a>). <p> This picture shows the disk pack being reinserted into the drive. Unlike modern hard disk drives, the Alto's disk can be removed from the drive. Users typically used different disks for different tasks — a programming disk, a word processing disk, and so forth. The disk pack is a fairly large white package, resembling a cross between an overgrown Frisbee and a poorly-detailed Star Wars spaceship. The drive's multiple circuit boards are also visible in the photo.<a class="ref" href="#ref4">[4]</a> <p> <a href="//static.righto.com/images/alto/IMG_20160611_151305.jpg"><img alt="Inserting a 2.5 MB hard disk pack into the Diablo drive used by the Xerox Alto computer." class="hilite" height="450" src="//static.righto.com/images/alto/IMG_20160611_151305-w600.jpg" title="Inserting a 2.5 MB hard disk pack into the Diablo drive used by the Xerox Alto computer." width="600"> </a> <p> <div class="cite"> Inserting a 2.5 MB hard disk pack into the Diablo drive used by the Xerox Alto computer. </div> <p> As the disk pack enters the drive, it opens up to provide access to the disk surface. The photo below shows the exposed surface of the disk, brownish from the magnetizable iron oxide layer over the aluminum platter. The read/write head is visible above the disk's surface, with another head below the disk. The disk stores data in 203 concentric pairs of tracks, with the heads moving in and out together to access each pair of tracks. <p> <a href="//static.righto.com/images/alto/IMG_20160611_151324.jpg"><img alt="Closeup of the hard disk inside the Diablo drive. The read/write head (metal/yellow) is visible above the disk surface (brown)." class="hilite" height="450" src="//static.righto.com/images/alto/IMG_20160611_151324-w600.jpg" title="Closeup of the hard disk inside the Diablo drive. The read/write head (metal/yellow) is visible above the disk surface (brown)." width="600"> </a> <p> <div class="cite"> Closeup of the hard disk inside the Diablo drive. The read/write head (metal/yellow) is visible above the disk surface (brown). </div> <p> Although the heads are widely separated during disk pack insertion, they move very close to the disk surface during operation, floating about one thousandth of a millimeter above the surface. The diagram below from the <a href="http://bitsavers.org/pdf/xerox/alto/AltoDisc.pdf">manual</a> helps visualize this minute distance, and illustrates the danger of particles on the disk's surface. <p> <a href="//static.righto.com/images/alto/crash.jpg"><img alt="The Diablo disk and why contaminants are bad, from the Alto disk manual." class="hilite" height="299" src="//static.righto.com/images/alto/crash-w450.jpg" title="The Diablo disk and why contaminants are bad, from the Alto disk manual." width="450"> </a> <p> <div class="cite"> The Diablo disk and why contaminants are bad, from the Alto disk manual. </div> <h2>The disk interface cliffhanger</h2> The final activity of the day was making sure all the Alto's circuit boards were in the right slots and the cables were all hooked up properly.<a class="ref" href="#ref5">[5]</a> Everything went smoothly until I tried to hook up the Diablo disk drive to the disk interface card: the disk drive cable didn't fit on the card's connector! <p> <a href="//static.righto.com/images/alto/disk_cable.jpg"><img alt="The cable to the Alto disk didn't fit onto the disk interface card!" class="hilite" height="370" src="//static.righto.com/images/alto/disk_cable-w400.jpg" title="The cable to the Alto disk didn't fit onto the disk interface card!" width="400"> </a> <p> <div class="cite"> The cable to the Alto disk didn't fit onto the disk interface card! </div> <p> After trying various combinations of cables and edge connectors, we discovered that the rainbow-colored ribbon cable you can see in the lower right above did fit the disk interface card. But instead of going to the Diablo disk drive, this cable went to a connector on the back of the Alto labeled "Tricon". Tricon is the controller for the <a href="http://bitsavers.informatik.uni-stuttgart.de/pdf/xerox/alto/ifs_trident/TriconDoc.pdf">Trident Disk</a>, a high-capacity disk drive that could be used with the Alto, providing 80 MB instead of the just 2.5 MB that the standard Diablo drive provides. Looking at the disk interface card more closely, we saw it was labeled "Alto II Trident Disk Interface" (upper left corner of the photo below), confirming that it was for the Trident. <p> <a href="//static.righto.com/images/alto/trident_card.jpg"><img alt="Trident Disk Interface card for Xerox Alto computer. (See label in upper left.)" class="hilite" height="383" src="//static.righto.com/images/alto/trident_card-w600.jpg" title="Trident Disk Interface card for Xerox Alto computer. (See label in upper left.)" width="600"> </a> <p> <div class="cite"> Trident Disk Interface card for Xerox Alto computer. (See label in upper left.) </div> <p> It was a shock to discover the disk interface card was for the Trident drive, since our Alto has the standard Diablo drive, which is completely incompatible with the Trident.<a class="ref" href="#ref6">[6]</a> We checked all the boards and verified that the system was missing the Diablo interface board. This was a showstopper problem; with the wrong board, the disk drive would be unusable and we wouldn't be able to boot up the system. What could we do? Network boot the Alto? Build a disk simulator? Find a Trident drive on eBay? (We actually found a <a href="http://www.ebay.com/itm/ALTO-II-DISK-PLATTER-TRIDENT-T-80-BY-CENTURY-DATA-SYSTEMS-A-XEROX-COMPANY-/301877515287?hash=item46494d5417:g:UhMAAOSwDuJWyOCy">Trident disk platter</a> on eBay for $129, but no drive.) <p> Tune in next episode to find out what we did about the disk interface problem. (Spoiler: we found a solution thanks to Al Kossow.) <h2>Notes and references</h2> <a name="ref1"></a>[1] The physical layout of the power supplies is specified on page 11 of <a href="http://bitsavers.org/pdf/xerox/alto/schematics/01a_INTRO.pdf">the Alto documentation introduction</a>. On the top are three Raytheon/Sorensen power supplies, +12V (15A), +15V (12A), and -15V (12A). At the bottom is a large LH Research Mighty Mite power supply providing +5V (60A) and -5V (12A). <p> Why the variety of voltages? Most of the circuitry in the Alto uses 5V, which is standard for TTL chips. The <a href="http://www.rogtronics.net/files/datasheets/mem_dram/TMS4116.pdf">MOS memory chips</a> use +5V, -5V and +12V. The Ethernet card uses +15V and -15V, with +15V powering the transceiver. The disk drive uses +/- 15V. <p> <a name="ref2"></a>[2] Steve Jobs claimed that the Apple II's use of a switching power supply was a revolutionary idea ripped off by other computer manufacturers. However, the Alto is just one of many computers that used switching power supplies before Apple (<a href="http://www.righto.com/2012/02/apple-didnt-revolutionize-power.html">details</a>). <p> <a name="ref3"></a>[3] For full details on the power supply operation, see the <a href="//static.righto.com/images/alto/block_diagram.jpg">block diagram</a>. First, the 115V AC line input is converted to 300V DC by a rectifier and voltage doubler. (The <a href="https://en.wikipedia.org/wiki/Voltage_doubler#Bridge_circuit">voltage doubler</a> is a clever way of supporting both 115V and 230V inputs; using the doubler with 115V. This is why older PCs have a switch on the power supply to select 115V or 230V. Modern power supplies handle a wide input range, and don't require a switch.) Next, the power supply has a <i>chopper</i>, a PWM transistor circuit that chops up the 300V DC, producing a regulated 120V-200V DC, depending on the output load. This goes to the <i>inverter</i>, which drives a step-down/isolation transformer that produces the desired 15V output. A regulation circuit sends feedback to the chopper based on the output voltage. Meanwhile, an entirely separate switching power supply circuit generates voltages (including +150V) used by the power supply internally. <p> Modern power supplies use a single switching stage in place of the separate chopper and inverter. I believe the two stages were used to reduce the load on the bipolar switching transistors, which don't have the performance of modern MOSFET switching transistors. (As Ron pointed out, modern power supplies often have a PFC (power factor correction) stage for improved efficiency. Thus, the two-stage design has returned, although the stages are entirely different now.) <p> Modern power supplies use a power supply control IC. The Alto's power supply instead has control circuits built from simple components: transistors, op amps, 555 timers. This is one reason the power supply requires three circuit boards. <p> <a name="ref4"></a>[4] The following table from the <a href="http://bitsavers.org/pdf/xerox/alto/AltoDisc.pdf">Alto disk manual</a> gives the stats for the drive. <p> <a href="//static.righto.com/images/alto/stats.jpg"><img alt="Statistics on the Diablo 31 disk used with the Xerox Alto computer." class="hilite" height="391" src="//static.righto.com/images/alto/stats-w350.jpg" title="Statistics on the Diablo 31 disk used with the Xerox Alto computer." width="350"> </a> <p> <div class="cite"> Statistics on the Diablo 31 disk used with the Xerox Alto computer. </div> <p> <a name="ref5"></a>[5] The Alto backplane has 21 slots, not all of which are used in our system. The list of which board goes into which slot is on page 8 of <a href="http://bitsavers.org/pdf/xerox/alto/schematics/01a_INTRO.pdf">the Alto documentation</a>. <p> <a name="ref6"></a>[6] I suspect that the Y Combinator Alto originally had both a Trident drive and a Diablo drive (as well as four Orbit boards to drive a laser printer), and when it was taken out of service, the Trident drive, the Diablo interface board, and the Orbit boards went off somewhere else. This left the Alto with a drive that didn't match the interface card. <p> For reference, schematics and documentation on the Trident interface board are <a href="http://bitsavers.org/pdf/xerox/alto/ifs_trident/Tricon.pdf">here</a>. Despite all the chips on the disk interface board, it doesn't do very much, since each TTL chip is fairly simple. The interface board has some counters, one word data buffers, parallel/serial conversion, and a bit of control logic. The Alto was designed to offload many hardware tasks to microcode, so the hard work of disk I/O is performed in microcode (software). <p> <div style='clear: both;'></div> </div> <div class='post-footer'> <div class='post-footer-line post-footer-line-1'><span class='post-comment-link'> <a class='comment-link' href='https://www.blogger.com/comment/fullpage/post/6264947694886887540/8792262437996446798' onclick=''> 6 comments: </a> </span> <span class='post-icons'> <span class='item-action'> <a href='https://www.blogger.com/email-post/6264947694886887540/8792262437996446798' title='Email Post'> <img alt='' class='icon-action' height='13' src='http://img1.blogblog.com/img/icon18_email.gif' width='18'/> </a> </span> <span class='item-control blog-admin pid-1138732533'> <a href='https://www.blogger.com/post-edit.g?blogID=6264947694886887540&postID=8792262437996446798&from=pencil' title='Edit Post'> <img alt='' class='icon-action' height='18' src='https://resources.blogblog.com/img/icon18_edit_allbkg.gif' width='18'/> </a> </span> </span> <span class='post-backlinks post-comment-link'> </span> <div class='post-share-buttons goog-inline-block'> <a class='goog-inline-block share-button sb-email' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=8792262437996446798&target=email' target='_blank' title='Email This'><span class='share-button-link-text'>Email This</span></a><a class='goog-inline-block share-button sb-blog' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=8792262437996446798&target=blog' onclick='window.open(this.href, "_blank", "height=270,width=475"); return false;' target='_blank' title='BlogThis!'><span class='share-button-link-text'>BlogThis!</span></a><a class='goog-inline-block share-button sb-twitter' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=8792262437996446798&target=twitter' target='_blank' title='Share to X'><span class='share-button-link-text'>Share to X</span></a><a class='goog-inline-block share-button sb-facebook' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=8792262437996446798&target=facebook' onclick='window.open(this.href, "_blank", "height=430,width=640"); return false;' target='_blank' title='Share to Facebook'><span class='share-button-link-text'>Share to Facebook</span></a><a class='goog-inline-block share-button sb-pinterest' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=8792262437996446798&target=pinterest' target='_blank' title='Share to Pinterest'><span class='share-button-link-text'>Share to Pinterest</span></a> </div> </div> <div class='post-footer-line post-footer-line-2'><span class='post-labels'> Labels: <a href='http://www.righto.com/search/label/alto' rel='tag'>alto</a>, <a href='http://www.righto.com/search/label/electronics' rel='tag'>electronics</a>, <a href='http://www.righto.com/search/label/power%20supply' rel='tag'>power supply</a> </span> </div> <div class='post-footer-line post-footer-line-3'></div> </div> </div> </div> </div></div> <div class="date-outer"> <div class="date-posts"> <div class='post-outer'> <div class='post hentry' itemprop='blogPost' itemscope='itemscope' itemtype='http://schema.org/BlogPosting'> <meta content='https://i.ytimg.com/vi/YupOC_6bfMI/hqdefault.jpg' itemprop='image_url'/> <meta content='6264947694886887540' itemprop='blogId'/> <meta content='1813630973213822814' itemprop='postId'/> <a name='1813630973213822814'></a> <h3 class='post-title entry-title' itemprop='name'> <a href='http://www.righto.com/2016/06/y-combinators-xerox-alto-restoring.html'>Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer</a> </h3> <div class='post-header'> <div class='post-header-line-1'></div> </div> <div class='post-body entry-content' id='post-body-1813630973213822814' itemprop='description articleBody'> <meta property="og:image" content="//static.righto.com/images/alto/alto-s640.jpg" /> <p> Alan Kay recently gave his 1970's Xerox Alto to Y Combinator and I'm helping with the restoration of this legendary system. The Alto was the first computer designed around a graphical user interface and introduced Ethernet and the laser printer<a class="ref" href="#ref1">[1]</a> to the world. The Alto also was one of the first object-oriented systems, supporting the Mesa and Smalltalk languages. The Alto was truly revolutionary when it came out in 1973, designed by computer pioneer <a href="https://en.wikipedia.org/wiki/Charles_P._Thacker">Chuck Thacker</a>. <p> <iframe width="560" height="315" src="https://www.youtube.com/embed/YupOC_6bfMI?rel=0" frameborder="0" allowfullscreen></iframe> <p> Xerox built about 2000 Altos for use in Xerox, universities and research labs, but the Alto was never sold as a product. Xerox used the ideas from the Alto in the <a href="https://en.wikipedia.org/wiki/Xerox_Star">Xerox Star</a>, which was expensive and only moderately successful. The biggest impact of the Alto was in 1979 when Steve Jobs famously toured Xerox and saw the Alto and other machines. When Jobs saw the advanced graphics of the Alto, he was inspired to base the user interfaces of the Lisa and Macintosh systems on Xerox's ideas, making the GUI available to the mass market.<a class="ref" href="#ref2">[2]</a> <p> How did Y Combinator end up with a Xerox Alto? Sam Altman, president of Y Combinator has a strong interest in the Alto and its place in computer history. When he mentioned to Alan Kay that it would be fun to see one running, Alan gave him one. <p> This article gives an overview of the Alto, its impact, and how it was implemented. Later articles will discuss the restoration process as we fix components that have broken over the decades and get the system running. <p> <a href="//static.righto.com/images/alto/alto.jpg"><img alt="The Xerox Alto II XM computer. Note the video screen is arranged in portrait mode. Next to the keyboard is a mouse. The Diablo disk drive is below the keyboard. The base contains the circuit boards and power supplies." class="hilite" height="515" src="//static.righto.com/images/alto/alto-w300.jpg" title="The Xerox Alto II XM computer. Note the video screen is arranged in portrait mode. Next to the keyboard is a mouse. The Diablo disk drive is below the keyboard. The base contains the circuit boards and power supplies." width="300"> </a> <p> <div class="cite"> The Xerox Alto II XM computer. Note the video screen is arranged in portrait mode. Next to the keyboard is a mouse. The Diablo disk drive is below the keyboard. The base contains the circuit boards and power supplies. </div> <p> The photo above shows Y Combinator's Alto computer. The Alto has an unusual portrait-format display, intended to match an 8½" by 11" page of paper. Most displays of the time were character-oriented, but the Alto had a bitmapped display, with each of the 606x808 pixels controllable independently. This provided unprecedented flexibility for the display and allowed WYSIWYG (what-you-see-is-what-you-get) editing. The bitmapped display memory used almost half the memory of the original Alto, however <p> In front of the keyboard is the three-button mouse. Xerox made the mouse a fundamental input device for the Alto and designed the user interface around the mouse. The disk drive at the top of the cabinet takes a removable 2.5 megabyte disk cartridge. The small capacity of the disk was a problem for users, but files could also be accessed over the Ethernet from file servers. The lower part of the cabinet contains the computer's circuit boards and power supplies, which will be discussed below. <h2>Dynabook and the vision of the Alto</h2> The motivation for the Alto was Alan Kay's Dynabook project. In 1972, he wrote <a href="http://history-computer.com/Library/Kay72.pdf">A Personal Computer for Children of All Ages</a>, setting out his vision for a personal, portable computer for education (or business), with access to the world's knowledge. In effect, Alan Kay presented a detailed vision for the touchscreen tablet decades before it was practical.<a class="ref" href="#ref3">[3]</a> <p> <a href="//static.righto.com/images/alto/alan_kay.jpg"><img alt="Alan Kay with a mockup of the Dynabook. Photo by Marcin Wichary, CC BY 2.0." class="hilite" src="//static.righto.com/images/alto/alan_kay-w300.jpg" title="Alan Kay with a mockup of the Dynabook. Photo by Marcin Wichary, CC BY 2.0." width="300"> </a> <p> <div class="cite"> Alan Kay with a mockup of the Dynabook. Although the Dynabook was proposed years before the necessary hardware was available, the ideas could be tried out on the Alto, an "interim Dynabook". Photo by <a href="https://www.flickr.com/photos/mwichary/3010043854">Marcin Wichary</a>, <a href="https://creativecommons.org/licenses/by/2.0/">CC BY 2.0</a>. </div> The Dynabook (seen in mockup above) was to be a low-cost, battery-powered, portable computer with a touchscreen and graphics, able to access information over the network. The system would be highly interactive and programmable in an object-oriented language. As well as the keyboard, voice input could be used. Books could be downloaded and purchased. <p> Since the necessary hardware was science fiction when the Dynabook was proposed, the Alto was built as an "interim Dynabook" for research. Butler Lampson's <a href="http://research.microsoft.com/en-us/um/people/blampson/38a-WhyAlto/Acrobat.pdf">1972 memo</a> entitled "Why Alto" proposed using the Alto for research in distributed computing, office computing, graphics, and personal computing. He stated, "If our theories about the utility of cheap, powerful personal computers are correct, we should be able to demonstrate them convincingly on Alto." Xerox used the Alto to research and develop the ideas of personal computing.<a class="ref" href="#ref4">[4]</a> <p> <h2>Software</h2> The Alto had a <a href="https://www.mirrorservice.org/sites/www.bitsavers.org/pdf/xerox/alto/memos_1981/Alto_Subsystems_May81.pdf">large collection of software</a>, largely implemented in the BCPL (predecessor to C), Mesa and Smalltalk languages. The <i>Bravo</i> text editor (seen below) is considered the first <a href="https://en.wikipedia.org/wiki/WYSIWYG#History">WYSIWYG</a> editor, with formatted text on the screen matching the laser printer output. Also below is the <i>Draw</i> illustration program which used the mouse and an icon menu to create drawings. Other significant programs included email, file transfer (FTP) and an integrated circuit editor. The Alto also ran some of the first networked multiplayer games such as <a href="https://en.wikipedia.org/wiki/Alto_Trek">Alto Trek</a> and <a href="http://www.digibarn.com/collections/games/xerox-maze-war/">Maze War</a>. <p> <a href="//static.righto.com/images/alto/alto_bravo.png"><img alt="Bravo was the word processor for the Xerox Alto, providing WYSIWYG text editing." class="hilite" src="//static.righto.com/images/alto/alto_bravo-w450.png" style="border: 2px solid #ccc" title="Bravo was the word processor for the Xerox Alto, providing WYSIWYG text editing." width="450"></a> <a href="//static.righto.com/images/alto/alto_draw.png"><img alt="The Draw program for the Xerox Alto uses the mouse and icons for drawing." class="hilite" src="//static.righto.com/images/alto/alto_draw-w450.png" style="border:2px solid #ccc" title="The Draw program for the Xerox Alto uses the mouse and icons for drawing." width="450"> </a> <p> <div class="cite"> Bravo was the word processor for the Xerox Alto, providing WYSIWYG text editing. The Draw program for the Xerox Alto uses the mouse and icons for drawing. The Alto simulator <a href="http://www.computerhistory.org/atchm/xerox-alto-source-code/">Salto</a> was used for these images. </div> <h2>Hardware</h2> The Alto was introduced in 1973. To understand this time in computer hardware, the primitive 4004 microprocessor had been introduced a couple years earlier. Practical microprocessors such as the 6502 and Z-80 were still a couple years in the future and the Apple II wouldn't be released until 1977. At the time, minicomputers such as the Data General Nova and PDP-11 built processors out of hundreds of simple but fast TTL integrated circuits, rather than using slow, unreliable MOS chips. The Alto was built similarly, and is a minicomputer, not a microcomputer.<a class="ref" href="#ref5">[5]</a> <p> The Alto has 13 circuit boards, crammed full of chips. Each board is a bit smaller than a page of paper, about 7-5/16" by 10", and holds roughly 100 chips (depending on the board). For the most part, the chips are bipolar TTL chips in the popular 7400 series. (The MOS memory chips are an exception.) The image below shows the Alto's card rack and some of the boards. <p> <a href="//static.righto.com/images/alto/alto_cards.jpg"><img alt="The Xerox Alto contains 21 slots for circuit boards. Each board is crammed with chips, mostly TTL." class="hilite" height="532" src="//static.righto.com/images/alto/alto_cards-w400.jpg" title="The Xerox Alto contains 21 slots for circuit boards. Each board is crammed with chips, mostly TTL." width="400"> </a> <p> <div class="cite"> The Xerox Alto contains 21 slots for circuit boards. Each board is crammed with chips, mostly TTL. </div> <p> The Alto's CPU consists of three boards. The <i>Control</i> board is the heart of the processor: it manages the 16 microcode tasks and contains microcode in PROM. The <i>ALU</i> board performs arithmetic and logic operations, and provides the main register storage. The <i>Control RAM</i> board provides additional microcode storage in RAM and additional processor registers. (Note that in a few years, a single chip microprocessor could replace these three boards.) <p> The photo below shows the ALU board. The 16-bit addition, subtraction and Boolean operations are performed by four of the popular <a href="https://en.wikipedia.org/wiki/74181">74181</a> ALU chip, used in many other processors of the era. Each 16-bit register requires multiple chips for storage. The 32x16 register file is historically interesting as it is built from i3101 64-bit bipolar memory chips, Intel's first-ever product. <p> <a href="//static.righto.com/images/alto/alu.jpg"><img alt="The ALU board from the Xerox Alto." class="hilite" height="375" src="//static.righto.com/images/alto/alu-w600.jpg" title="The ALU board from the Xerox Alto." width="600"> </a> <p> <div class="cite"> The ALU board from the Xerox Alto. </div> <p> The Alto came out at a time when memory was expensive and somewhat unreliable.<a class="ref" href="#ref6">[6]</a> In 1970, Intel introduced the first commercially available DRAM memory, the <a href="https://en.wikipedia.org/wiki/Intel_1103">1103</a> chip, holding 1 kilobit of storage and making <a href="http://www.righto.com/2015/08/examining-core-memory-module-inside.html">magnetic core memory</a> obsolete. The original Alto used 16 boards crammed full of these chips to provide 128 kilobytes of memory. The Alto we have is a more modern Alto II XM (eXtended Memory) with 512 kilobytes of storage on four boards. Even so, the limited memory capacity was a difficulty for programmers and users. The photo below shows one of the memory board, packed with denser <a href="http://smithsonianchips.si.edu/augarten/p50.htm">16 kilobit</a> chips. <p> <a href="//static.righto.com/images/alto/1-memory_card.jpg"><img alt="A 128KB memory card from the Xerox Alto." class="hilite" height="207" src="//static.righto.com/images/alto/memory_card-w400.jpg" title="A 128KB memory card from the Xerox Alto." width="400"> </a> <p> <div class="cite"> A 128KB memory card from the Xerox Alto. It uses eighty 4116 memory chips, each with 16 kilobits of storage. </div> <h2>Microcode</h2> The Alto hardware provides a simple micro-instruction set and uses microcode to implement a full instruction set on top of this,<a class="ref" href="#ref7">[7]</a> including some very complex instructions. The Alto introduced the <code>BITBLT</code> graphics instruction, which draws an arbitrary bitmap to the display in a variety of ways (e.g. paint over, gray stipple or XOR). "Blitting" became a standard graphics operation, still be found in <a href="https://msdn.microsoft.com/en-us/library/windows/desktop/dd183370(v=vs.85).aspx">Windows</a>. <p> The Alto takes microcode further than most computers, implementing many functions in microcode that most computers implement in hardware, making the Alto hardware simpler and more flexible.<a class="ref" href="#ref8">[8]</a> Microcode tasks copy every pixel to the display 30 times a second, refresh dynamic memory, read the mouse, handle disk operations, drive Ethernet — operations performed in hardware on most computers. Much of the Alto microcode is stored in RAM, so languages or even user programs can run custom microcode. <h2>Next steps</h2> The first step to getting the system running will be to make sure the power supplies work and provide the proper voltages. The Alto uses four complex but highly efficient switching power supplies: +15V, -15V, +12V, and +/-5V.<a class="ref" href="#ref9">[9]</a> (Most of the chips use +5V, but the memory chips and some interfaces require unusual voltages.) <p> The power supplies are mounted in the cabinet behind the card cage, as you can see in the photo below. The +/-5V supply is on the right, and the three other power supplies are on the left. <p> <a href="//static.righto.com/images/alto/alto_back.jpg"><img alt="Looking into the back of the Alto, you can see the four switching power supplies (blue). The card cage is behind them. The disk drive has been removed from the top of the cabinet. On the back of the cabinet, connectors to the display, Ethernet, and other devices are visible." class="hilite" height="394" src="//static.righto.com/images/alto/alto_back-w350.jpg" title="Looking into the back of the Alto, you can see the four switching power supplies (blue). The card cage is behind them. The disk drive has been removed from the top of the cabinet. On the back of the cabinet, connectors to the display, Ethernet, and other devices are visible." width="350"> </a> <p> <div class="cite"> Looking into the back of the Alto, you can see the four switching power supplies (blue). The card cage is behind them. The disk drive has been removed from the top of the cabinet. On the back of the cabinet, connectors to the display, Ethernet, and other devices are visible. </div> <p> Restoring this systems is a big effort but fortunately there's a strong team working on it, largely from the <a href="http://ibm-1401.info/">IBM 1401 restoration team</a>. The main Alto restorers so far are Marc Verdiell, Luca Severini, Ron, and Carl Claunch. Major technical contributions have been provided by <a href="http://www.computerhistory.org/staff/Al,Kossow/">Al Kossow</a> (who has done extensive Alto restoration work in the past and is at the <a href="http://www.computerhistory.org/">Computer History Museum</a>) and the two Keiths (who have restored Altos at the <a href="http://www.livingcomputermuseum.org/">Living Computer Museum</a>). For updates on the restoration, follow <a href="https://twitter.com/kenshirriff">kenshirriff</a> on Twitter.<a class="ref" href="#ref10">[10]</a> <h2>Notes and references</h2> <a name="ref1"></a>[1] The laser printer was invented at Xerox by <a href="https://en.wikipedia.org/wiki/Gary_Starkweather">Gary Starkweather</a> and networked laser printers were soon in use with the Alto. Y Combinator's Alto is an "Orbit" model, with slots for the four boards that drive the laser printer, laboriously rendering 16 rows of pixels at a time. <p> <a name="ref2"></a>[2] Malcolm Gladwell describes Steve Jobs' visit to Xerox in detail in <a href="http://www.newyorker.com/magazine/2011/05/16/creation-myth">Creation Myth</a>. The article claims that Xerox licensed its technology to Apple, but strangely that license wasn't mentioned in <a href="http://www.nytimes.com/1989/12/15/business/company-news-xerox-sues-apple-computer-over-macintosh-copyright.html">earlier articles</a> about Xerox's lawsuit against Apple. The facts here seem murky. <p> <a name="ref3"></a>[3] Amazingly, Alan Kay even predicted ad blockers in his 1972 Dynabook paper: "One can imagine one of the first programs an owner will write is a filter to eliminate advertising!" I thought that Alan Kay missed WiFi in the Dynabook design, but as he points out in the comments, wireless networking was a Dynabook feature. <p> <a name="ref4"></a>[4] Xerox called the Alto "a small personal computing system", saying, "By 'personal computer' we mean a non-shared system containing sufficient processing power, storage, and input-output capability to satisfy the computational needs of a single user." (See <a href="https://www.mirrorservice.org/sites/www.bitsavers.org/pdf/xerox/alto/Alto_Hardware_Manual_Aug76.pdf">ALTO: A Personal Computer System Hardware Manual</a>.) Xerox's vision of personal computing is described in the retrospective <a href="http://research.microsoft.com/en-us/um/people/blampson/25-Alto/25-Alto.pdf">Alto: A personal computer</a>. <p> Since the concept of "personal computer" is ill-defined, I won't argue whether the Alto is really a personal computer or not. Costing tens of thousands of dollars, the Alto was much more expensive than what people usually think of as a personal computer. The book <a href="http://amzn.to/1tB2s3B">Fumbling the Future: How Xerox Invented, then Ignored, the First Personal Computer</a> calls Xerox the inventor of the personal computer. (Or you can read <a href="http://amzn.to/21rz4XD">Datapoint: The Lost Story of the Texans Who Invented the Personal Computer Revolution</a>, which makes a convincing case for the <a href="https://en.wikipedia.org/wiki/Datapoint_2200">Datapoint 2200</a> as the first personal computer.) For a long list of candidates for the first personal computer, see <a href="http://www.blinkenlights.com/pc.shtml">blinkenlights.com</a>. <p> <a name="ref5"></a>[5] The Alto documentation refers to the <i>microprocessor</i>, but this term describes the microcode processor. The Alto does not use a microprocessor in the modern sense. <p> <a name="ref6"></a>[6] Since memory chips of the era were somewhat unreliable (especially in large quantities), the Alto used parity plus 6 bits of error correcting code to improve reliability. As well as the four memory boards, the Alto has three memory control boards to decode addresses and implement error correction. <p> <a name="ref7"></a>[7] The Alto's microcode instructions and "real" instructions (called Emulated Instructions) are described in the <a href="http://bitsavers.trailing-edge.com/pdf/xerox/alto/AltoHWRef.part1.pdf">Hardware Reference</a>. The Alto's instruction set is similar to the <a href="https://en.wikipedia.org/wiki/Data_General_Nova#Instruction_set">Data General Nova</a>. <p> <a name="ref8"></a>[8] The Alto has 16 separate microcode tasks, scheduled based on their priority. The Alto's microcode tasks are described in Appendix D of the <a href="http://bitsavers.trailing-edge.com/pdf/xerox/alto/AltoHWRef.part2.pdf">Hardware Manual</a>. The display task illustrates how low-level the microcode tasks are. In a "normal" computer, the display control hardware fetches pixels from memory. In the Alto, the display task in microcode copies pixels from memory to the display hardware's 16 word pixel buffer as each line is being written to the display. The point is that the hardware is simplified, but the microcode task is working very hard, copying every pixel to the display 30 times a second. Similarly the Ethernet hardware is simplified, since the microcode task does much of the work. <p> <a name="ref9"></a>[9] Steve Jobs claimed that the Apple II's use of a switching power supply was a revolutionary idea ripped off by other computer manufacturers. However, the Alto is just one of many computers that used switching power supplies before Apple (<a href="http://www.righto.com/2012/02/apple-didnt-revolutionize-power.html">details</a>). <p> <a name="ref10"></a>[10] Many sources have additional information on the Alto. Bitsavers has a <a href="http://bitsavers.org/pdf/xerox/alto/">large collection</a> of Alto documentation. <a href="http://www.digibarn.com/collections/systems/xerox-alto/index.html">DigiBarn</a> has photos and more information on the Alto. The Computer History Museum has a large collection of Alto source code online <a href="http://www.computerhistory.org/atchm/xerox-alto-source-code/">here</a>. The Alto simulator Salto is available <a href="http://www.computerhistory.org/atchm/xerox-alto-source-code/">here</a> if you want to try out the Alto experience. <a href="https://en.wikipedia.org/wiki/Xerox_Alto">Wikipedia</a> has a detailed article on the Alto. <p> <div style='clear: both;'></div> </div> <div class='post-footer'> <div class='post-footer-line post-footer-line-1'><span class='post-comment-link'> <a class='comment-link' href='https://www.blogger.com/comment/fullpage/post/6264947694886887540/1813630973213822814' onclick=''> 26 comments: </a> </span> <span class='post-icons'> <span class='item-action'> <a href='https://www.blogger.com/email-post/6264947694886887540/1813630973213822814' title='Email Post'> <img alt='' class='icon-action' height='13' src='http://img1.blogblog.com/img/icon18_email.gif' width='18'/> </a> </span> <span class='item-control blog-admin pid-1138732533'> <a href='https://www.blogger.com/post-edit.g?blogID=6264947694886887540&postID=1813630973213822814&from=pencil' title='Edit Post'> <img alt='' class='icon-action' height='18' src='https://resources.blogblog.com/img/icon18_edit_allbkg.gif' width='18'/> </a> </span> </span> <span class='post-backlinks post-comment-link'> </span> <div class='post-share-buttons goog-inline-block'> <a class='goog-inline-block share-button sb-email' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=1813630973213822814&target=email' target='_blank' title='Email This'><span class='share-button-link-text'>Email This</span></a><a class='goog-inline-block share-button sb-blog' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=1813630973213822814&target=blog' onclick='window.open(this.href, "_blank", "height=270,width=475"); return false;' target='_blank' title='BlogThis!'><span class='share-button-link-text'>BlogThis!</span></a><a class='goog-inline-block share-button sb-twitter' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=1813630973213822814&target=twitter' target='_blank' title='Share to X'><span class='share-button-link-text'>Share to X</span></a><a class='goog-inline-block share-button sb-facebook' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=1813630973213822814&target=facebook' onclick='window.open(this.href, "_blank", "height=430,width=640"); return false;' target='_blank' title='Share to Facebook'><span class='share-button-link-text'>Share to Facebook</span></a><a class='goog-inline-block share-button sb-pinterest' href='https://www.blogger.com/share-post.g?blogID=6264947694886887540&postID=1813630973213822814&target=pinterest' target='_blank' title='Share to Pinterest'><span class='share-button-link-text'>Share to Pinterest</span></a> </div> </div> <div class='post-footer-line post-footer-line-2'><span class='post-labels'> Labels: <a href='http://www.righto.com/search/label/alto' rel='tag'>alto</a>, <a href='http://www.righto.com/search/label/electronics' rel='tag'>electronics</a> </span> </div> <div class='post-footer-line post-footer-line-3'></div> </div> </div> </div> </div></div> </div> <div class='blog-pager' id='blog-pager'> <span id='blog-pager-newer-link'> <a class='blog-pager-newer-link' href='http://www.righto.com/search?updated-max=2016-09-12T10:53:00-07:00&max-results=7&reverse-paginate=true' id='Blog1_blog-pager-newer-link' title='Newer Posts'>Newer Posts</a> </span> <span id='blog-pager-older-link'> <a class='blog-pager-older-link' href='http://www.righto.com/search?updated-max=2016-06-18T09:54:00-07:00&max-results=7' id='Blog1_blog-pager-older-link' title='Older Posts'>Older Posts</a> </span> <a class='home-link' href='http://www.righto.com/'>Home</a> </div> <div class='clear'></div> </div></div> </div> </div> <div class='column-left-outer'> <div class='column-left-inner'> <aside> </aside> </div> </div> <div class='column-right-outer'> <div class='column-right-inner'> <aside> <div class='sidebar section' id='sidebar-right-1'><div class='widget HTML' data-version='1' id='HTML2'> <div class='widget-content'> <style> @import url('https://fonts.googleapis.com/css?family=Montserrat:300,400,500,700'); .form-preview { display: flex; flex-direction: column; justify-content: center; margin-top: 30px; padding: clamp(17px, 5%, 40px) clamp(17px, 7%, 50px); max-width: 350px; min-height: 200px; border-radius: 6px; box-shadow: 0 5px 25px rgba(34, 60, 47, 0.25); } .form-preview, .form-preview *{ box-sizing: border-box; } .form-preview .preview-heading { width: 100%; } .form-preview .preview-heading h5{ margin-top: 0; margin-bottom: 0; } .form-preview .preview-input-field { margin-top: 20px; width: 100%; } .form-preview .preview-input-field input { width: 100%; height: 40px; border-radius: 6px; border: 2px solid #e9e8e8; background-color: #fff; outline: none; } .form-preview .preview-input-field input::placeholder, .form-preview .preview-input-field input { opacity: 0.5; color: #000; font-family: "Montserrat"; font-size: 14px; font-weight: 500; line-height: 20px; text-align: center; } .form-preview .preview-submit-button { margin-top: 10px; width: 100%; } .form-preview .preview-submit-button button { width: 100%; height: 40px; border: 0; border-radius: 6px; line-height: 0px; } .form-preview .preview-submit-button button:hover { cursor: pointer; } </style><form data-v-4c58e686="" action="https://api.follow.it/subscription-form/U3NBTmZKVkI1YVpCa000a0RCZHFiQ3FYMko1cWRTZTN6K3hJdWM2QWxJbE1uVXdXUHZZVzJVQzVLZGh5Y0RCVXB2d2JSTzBobGhuY0FsZnlHbVdFZ2VTN2Q4Vy84RnIxUTgzVlcrbXNIR0Y0aW93d3REM2J6VS9RL0gxWURnV1d8ZWN0YStwUWdWWUFiOTIyWDVGWjdYYVdGZEVNcC9qODZacjlwWXRIcEJQRT0=/8" method="post"><div data-v-4c58e686="" class="form-preview" style="background-color: rgb(255, 255, 255); border-style: solid; border-width: 1px; border-color: rgb(204, 204, 204); position: relative;"><div data-v-4c58e686="" class="preview-heading"><h5 data-v-4c58e686="" style="font-family: Montserrat; font-weight: bold; color: rgb(0, 0, 0); font-size: 12px; text-align: center;">Get new posts by email:</h5></div> <div data-v-4c58e686="" class="preview-input-field"><input data-v-4c58e686="" type="email" name="email" placeholder="Enter your email" spellcheck="false" /></div> <div data-v-4c58e686="" class="preview-submit-button"><button data-v-4c58e686="" type="submit" style="font-family: Montserrat; font-weight: bold; color: rgb(255, 255, 255); font-size: 12px; text-align: center; background-color: rgb(0, 0, 0);">Subscribe</button></div></div></form> </div> <div class='clear'></div> </div><div class='widget HTML' data-version='1' id='HTML3'> <h2 class='title'>About the site</h2> <div class='widget-content'> <a href="https://www.righto.com/p/index.html">Contact info and site index</a> </div> <div class='clear'></div> </div><div class='widget PopularPosts' data-version='1' id='PopularPosts1'> <h2>Popular Posts</h2> <div class='widget-content popular-posts'> <ul> <li> <div class='item-thumbnail-only'> <div class='item-thumbnail'> <a href='http://www.righto.com/2025/02/origin-of-mainframe-term.html' target='_blank'> <img alt='' border='0' src='https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_tBn8FvBqiMwzms-EFuXp1eiIU4jMqaiPFJCU3N_-Qf3sHaElH9d4-wXsPd2mB6_axF3QudwELGKIi4g_BAcLosIUU1tKA-rlnn84wF_7HA7_PaB-f8E5aFKo-HjAoY3wNR3g=w72-h72-p-k-no-nu'/> </a> </div> <div class='item-title'><a href='http://www.righto.com/2025/02/origin-of-mainframe-term.html'>The origin and unexpected evolution of the word "mainframe"</a></div> </div> <div style='clear: both;'></div> </li> <li> <div class='item-thumbnail-only'> <div class='item-thumbnail'> <a href='http://www.righto.com/2024/05/blog-post.html' target='_blank'> <img alt='' border='0' src='https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_tktDGU_AMxNBFlBi0Sih_5d1yAqXXDwfOCw7O0fsKQpQmkPuLmQfVBplLB4vwlxkL953PmzPBc3O4M1YHatxuJLvdWicjlWnZ8FcJ6tZz9c3BW1wHxnCiImVckYt1G0r0VrqzBnFVP9NXq2uvS8qJI=w72-h72-p-k-no-nu'/> </a> </div> <div class='item-title'><a href='http://www.righto.com/2024/05/blog-post.html'>Inside a vintage aerospace navigation computer of uncertain purpose</a></div> </div> <div style='clear: both;'></div> </li> <li> <div class='item-thumbnail-only'> <div class='item-thumbnail'> <a href='http://www.righto.com/2009/08/multi-protocol-infrared-remote-library.html' target='_blank'> <img alt='' border='0' src='https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_svNELWWhfuSoYm_24v_BoTbUwxJB5z-WMsm_EW84rDfL7JJHrp2NzfswjTXHp4oQw9iqV41pf-W8fEN_1lnWMWJ2SVTDjxvAt2tnM1kZsOPIY=w72-h72-p-k-no-nu'/> </a> </div> <div class='item-title'><a href='http://www.righto.com/2009/08/multi-protocol-infrared-remote-library.html'>A Multi-Protocol Infrared Remote Library for the Arduino</a></div> </div> <div style='clear: both;'></div> </li> <li> <div class='item-thumbnail-only'> <div class='item-thumbnail'> <a href='http://www.righto.com/2012/05/apple-iphone-charger-teardown-quality.html' target='_blank'> <img alt='' border='0' src='https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_uspYiruEXsrv1Tz2gooXTLDrxlHBMi0A_b5tCiTUxgzyH1OCwR8rqIAnoL937NiEEu22m-Yo_RXNnUaapg22EGGlIWn8XjfaHMaUhftz77OxepcO_NM0tMyRTXnnOtywhP2mepSyFJTZNWFLruW5QSzP4=w72-h72-p-k-no-nu'/> </a> </div> <div class='item-title'><a href='http://www.righto.com/2012/05/apple-iphone-charger-teardown-quality.html'>Apple iPhone charger teardown: quality in a tiny expensive package</a></div> </div> <div style='clear: both;'></div> </li> <li> <div class='item-thumbnail-only'> <div class='item-thumbnail'> <a href='http://www.righto.com/2014/12/inside-intel-1405-die-photos-of-shift.html' target='_blank'> <img alt='' border='0' src='https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_tMky87VHkoZ5ncRe_xfanTOYlbH-VB9gu3rSSEUWEUJRYsZGXrgrjLB-4qyIQofChcGLEzFFFdMPEUp9k5RlggSTGQhODkQYw29Bs1u6ittniyao_V9F_gJoAbiOmd7Q=w72-h72-p-k-no-nu'/> </a> </div> <div class='item-title'><a href='http://www.righto.com/2014/12/inside-intel-1405-die-photos-of-shift.html'>Inside the Intel 1405: die photos of a shift register memory from 1970</a></div> </div> <div style='clear: both;'></div> </li> <li> <div class='item-thumbnail-only'> <div class='item-thumbnail'> <a href='http://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html' target='_blank'> <img alt='' border='0' src='https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_sLRoRjJfMgzCpjuz43Aw9i0FPIzUYP3A8U_o8BaAYHa_KKAXaEQ5k4ulIs7TiP8iAM-uM_tedbVRKzrWNVqAWYdBJcxfbjEOZHDAbagm-vuW7BTjw6OdDX4VO--V3dySm-=w72-h72-p-k-no-nu'/> </a> </div> <div class='item-title'><a href='http://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html'>Mining Bitcoin with pencil and paper: 0.67 hashes per day</a></div> </div> <div style='clear: both;'></div> </li> <li> <div class='item-thumbnail-only'> <div class='item-thumbnail'> <a href='http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html' target='_blank'> <img alt='' border='0' src='https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_uDThXWTM7kGsHLT7GrcQ5h8DUxeD7X3mAcz-Ry_HKcDs_kWEcZYa94KkAFg2_HC-k_sM0mpeG3SP1061QdyyYK2mbiQMG_HDAW67J1IOk8snsDm1spWtux5Vojemg=w72-h72-p-k-no-nu'/> </a> </div> <div class='item-title'><a href='http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html'>A dozen USB chargers in the lab: Apple is very good, but not quite the best</a></div> </div> <div style='clear: both;'></div> </li> <li> <div class='item-thumbnail-only'> <div class='item-thumbnail'> <a href='http://www.righto.com/2025/01/its-time-to-abandon-cargo-cult-metaphor.html' target='_blank'> <img alt='' border='0' src='https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_shCh6Vh25iGl3wDfdazNh6a49HgDGcoj-oxD4IjcIFK99tp74nZfD1hrF-zDkC9K8_B_K8T9xKwjrhqQfPP7BTuY8c5mK9gNGOBHx4c59hFW4P-aN-qj5kvbdEvd0wmQ=w72-h72-p-k-no-nu'/> </a> </div> <div class='item-title'><a href='http://www.righto.com/2025/01/its-time-to-abandon-cargo-cult-metaphor.html'>The origin of the cargo cult metaphor</a></div> </div> <div style='clear: both;'></div> </li> </ul> <div class='clear'></div> </div> </div><div class='widget BlogSearch' data-version='1' id='BlogSearch1'> <h2 class='title'>Search This Blog</h2> <div class='widget-content'> <div id='BlogSearch1_form'> <form action='http://www.righto.com/search' class='gsc-search-box' target='_top'> <table cellpadding='0' cellspacing='0' class='gsc-search-box'> <tbody> <tr> <td class='gsc-input'> <input autocomplete='off' class='gsc-input' name='q' size='10' title='search' type='text' value=''/> </td> <td class='gsc-search-button'> <input class='gsc-search-button' title='search' type='submit' value='Search'/> </td> </tr> </tbody> </table> </form> </div> </div> <div class='clear'></div> </div><div class='widget Label' data-version='1' id='Label1'> <h2>Labels</h2> <div class='widget-content cloud-label-widget-content'> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/386'>386</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/6502'>6502</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/8008'>8008</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/8085'>8085</a> </span> <span class='label-size label-size-4'> <a dir='ltr' href='http://www.righto.com/search/label/8086'>8086</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/8087'>8087</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/8088'>8088</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/aerospace'>aerospace</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/alto'>alto</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/analog'>analog</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/Apollo'>Apollo</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/apple'>apple</a> </span> <span class='label-size label-size-4'> <a dir='ltr' href='http://www.righto.com/search/label/arc'>arc</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/arduino'>arduino</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/arm'>arm</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/beaglebone'>beaglebone</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/bitcoin'>bitcoin</a> </span> <span class='label-size label-size-1'> <a dir='ltr' href='http://www.righto.com/search/label/c%23'>c#</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/cadc'>cadc</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/calculator'>calculator</a> </span> <span class='label-size label-size-4'> <a dir='ltr' href='http://www.righto.com/search/label/chips'>chips</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/css'>css</a> </span> <span class='label-size label-size-1'> <a dir='ltr' href='http://www.righto.com/search/label/datapoint'>datapoint</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/dx7'>dx7</a> </span> <span class='label-size label-size-5'> <a dir='ltr' href='http://www.righto.com/search/label/electronics'>electronics</a> </span> <span class='label-size label-size-1'> <a dir='ltr' href='http://www.righto.com/search/label/f%23'>f#</a> </span> <span class='label-size label-size-1'> <a dir='ltr' href='http://www.righto.com/search/label/fairchild'>fairchild</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/fpga'>fpga</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/fractals'>fractals</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/genome'>genome</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/globus'>globus</a> </span> <span class='label-size label-size-1'> <a dir='ltr' href='http://www.righto.com/search/label/haskell'>haskell</a> </span> <span class='label-size label-size-1'> <a dir='ltr' href='http://www.righto.com/search/label/HP'>HP</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/html5'>html5</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/ibm'>ibm</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/ibm1401'>ibm1401</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/ibm360'>ibm360</a> </span> <span class='label-size label-size-4'> <a dir='ltr' href='http://www.righto.com/search/label/intel'>intel</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/ipv6'>ipv6</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/ir'>ir</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/java'>java</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/javascript'>javascript</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/math'>math</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/microcode'>microcode</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/oscilloscope'>oscilloscope</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/Pentium'>Pentium</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/photo'>photo</a> </span> <span class='label-size label-size-4'> <a dir='ltr' href='http://www.righto.com/search/label/power%20supply'>power supply</a> </span> <span class='label-size label-size-4'> <a dir='ltr' href='http://www.righto.com/search/label/random'>random</a> </span> <span class='label-size label-size-5'> <a dir='ltr' href='http://www.righto.com/search/label/reverse-engineering'>reverse-engineering</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/sheevaplug'>sheevaplug</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/snark'>snark</a> </span> <span class='label-size label-size-3'> <a dir='ltr' href='http://www.righto.com/search/label/space'>space</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/spanish'>spanish</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/synth'>synth</a> </span> <span class='label-size label-size-4'> <a dir='ltr' href='http://www.righto.com/search/label/teardown'>teardown</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/theory'>theory</a> </span> <span class='label-size label-size-1'> <a dir='ltr' href='http://www.righto.com/search/label/unicode'>unicode</a> </span> <span class='label-size label-size-2'> <a dir='ltr' href='http://www.righto.com/search/label/Z-80'>Z-80</a> </span> <div class='clear'></div> </div> </div><div class='widget BlogArchive' data-version='1' id='BlogArchive1'> <h2>Blog Archive</h2> <div class='widget-content'> <div id='ArchiveList'> <div id='BlogArchive1_ArchiveList'> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2025/'> 2025 </a> <span class='post-count' dir='ltr'>(5)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2025/02/'> February </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2025/01/'> January </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/'> 2024 </a> <span class='post-count' dir='ltr'>(21)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/12/'> December </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/11/'> November </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/10/'> October </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/09/'> September </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/08/'> August </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/07/'> July </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/06/'> June </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/05/'> May </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/04/'> April </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/03/'> March </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/02/'> February </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2024/01/'> January </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/'> 2023 </a> <span class='post-count' dir='ltr'>(35)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/12/'> December </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/11/'> November </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/10/'> October </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/09/'> September </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/08/'> August </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/07/'> July </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/05/'> May </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/04/'> April </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/03/'> March </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/02/'> February </a> <span class='post-count' dir='ltr'>(5)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2023/01/'> January </a> <span class='post-count' dir='ltr'>(8)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/'> 2022 </a> <span class='post-count' dir='ltr'>(18)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/11/'> November </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/08/'> August </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/07/'> July </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/06/'> June </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/05/'> May </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/04/'> April </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/03/'> March </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/02/'> February </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2022/01/'> January </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/'> 2021 </a> <span class='post-count' dir='ltr'>(26)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/12/'> December </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/11/'> November </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/09/'> September </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/08/'> August </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/07/'> July </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/06/'> June </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/05/'> May </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/04/'> April </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/03/'> March </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/02/'> February </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2021/01/'> January </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/'> 2020 </a> <span class='post-count' dir='ltr'>(33)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/12/'> December </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/11/'> November </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/10/'> October </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/09/'> September </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/08/'> August </a> <span class='post-count' dir='ltr'>(5)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/07/'> July </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/06/'> June </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/05/'> May </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/04/'> April </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/03/'> March </a> <span class='post-count' dir='ltr'>(5)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2020/01/'> January </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2019/'> 2019 </a> <span class='post-count' dir='ltr'>(18)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2019/11/'> November </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2019/10/'> October </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2019/09/'> September </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2019/08/'> August </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2019/07/'> July </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2019/04/'> April </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2019/02/'> February </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2019/01/'> January </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/'> 2018 </a> <span class='post-count' dir='ltr'>(17)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/12/'> December </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/09/'> September </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/08/'> August </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/06/'> June </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/05/'> May </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/04/'> April </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/03/'> March </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/02/'> February </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2018/01/'> January </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/'> 2017 </a> <span class='post-count' dir='ltr'>(21)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/12/'> December </a> <span class='post-count' dir='ltr'>(5)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/11/'> November </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/10/'> October </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/08/'> August </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/07/'> July </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/06/'> June </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/04/'> April </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/03/'> March </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/02/'> February </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2017/01/'> January </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate expanded'> <a class='toggle' href='javascript:void(0)'> <span class='zippy toggle-open'> ▼  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/'> 2016 </a> <span class='post-count' dir='ltr'>(34)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/12/'> December </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/10/'> October </a> <span class='post-count' dir='ltr'>(5)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/09/'> September </a> <span class='post-count' dir='ltr'>(8)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/08/'> August </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/07/'> July </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate expanded'> <a class='toggle' href='javascript:void(0)'> <span class='zippy toggle-open'> ▼  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/06/'> June </a> <span class='post-count' dir='ltr'>(4)</span> <ul class='posts'> <li><a href='http://www.righto.com/2016/06/hello-world-in-bcpl-language-on-xerox.html'>"Hello world" in the BCPL language on the Xerox Al...</a></li> <li><a href='http://www.righto.com/2016/06/inside-tiny-rfid-chip-that-runs-san.html'>Inside the tiny RFID chip that runs San Francisco'...</a></li> <li><a href='http://www.righto.com/2016/06/restoring-y-combinators-xerox-alto-day.html'>Restoring Y Combinator's Xerox Alto, day 1: Power ...</a></li> <li><a href='http://www.righto.com/2016/06/y-combinators-xerox-alto-restoring.html'>Y Combinator's Xerox Alto: restoring the legendary...</a></li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/05/'> May </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/04/'> April </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/03/'> March </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/02/'> February </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2016/01/'> January </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2015/'> 2015 </a> <span class='post-count' dir='ltr'>(12)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2015/12/'> December </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2015/11/'> November </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2015/10/'> October </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2015/08/'> August </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2015/05/'> May </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2015/03/'> March </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2015/02/'> February </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2014/'> 2014 </a> <span class='post-count' dir='ltr'>(13)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2014/12/'> December </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2014/10/'> October </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2014/09/'> September </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2014/05/'> May </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2014/03/'> March </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2014/02/'> February </a> <span class='post-count' dir='ltr'>(5)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/'> 2013 </a> <span class='post-count' dir='ltr'>(24)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/11/'> November </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/09/'> September </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/08/'> August </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/07/'> July </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/06/'> June </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/04/'> April </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/03/'> March </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/02/'> February </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2013/01/'> January </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2012/'> 2012 </a> <span class='post-count' dir='ltr'>(10)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2012/12/'> December </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2012/11/'> November </a> <span class='post-count' dir='ltr'>(5)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2012/10/'> October </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2012/05/'> May </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2012/03/'> March </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2012/02/'> February </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2011/'> 2011 </a> <span class='post-count' dir='ltr'>(11)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2011/12/'> December </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2011/07/'> July </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2011/05/'> May </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2011/04/'> April </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2011/03/'> March </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2011/02/'> February </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/'> 2010 </a> <span class='post-count' dir='ltr'>(22)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/12/'> December </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/11/'> November </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/10/'> October </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/08/'> August </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/06/'> June </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/05/'> May </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/04/'> April </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/03/'> March </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2010/01/'> January </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/'> 2009 </a> <span class='post-count' dir='ltr'>(22)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/12/'> December </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/11/'> November </a> <span class='post-count' dir='ltr'>(5)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/09/'> September </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/08/'> August </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/07/'> July </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/06/'> June </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/04/'> April </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/03/'> March </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/02/'> February </a> <span class='post-count' dir='ltr'>(2)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2009/01/'> January </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2008/'> 2008 </a> <span class='post-count' dir='ltr'>(27)</span> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2008/07/'> July </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2008/06/'> June </a> <span class='post-count' dir='ltr'>(1)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2008/05/'> May </a> <span class='post-count' dir='ltr'>(3)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2008/04/'> April </a> <span class='post-count' dir='ltr'>(4)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2008/03/'> March </a> <span class='post-count' dir='ltr'>(10)</span> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <a class='toggle' href='javascript:void(0)'> <span class='zippy'> ►  </span> </a> <a class='post-count-link' href='http://www.righto.com/2008/02/'> February </a> <span class='post-count' dir='ltr'>(6)</span> </li> </ul> </li> </ul> </div> </div> <div class='clear'></div> </div> </div></div> </aside> </div> </div> </div> <div style='clear: both'></div>  </div>  </div> </div> <div class='main-cap-bottom cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div> <footer> <div class='footer-outer'> <div class='footer-cap-top cap-top'> <div class='cap-left'></div> <div class='cap-right'></div> </div> <div class='fauxborder-left footer-fauxborder-left'> <div class='fauxborder-right footer-fauxborder-right'></div> <div class='region-inner footer-inner'> <div class='foot no-items section' id='footer-1'></div> <table border='0' cellpadding='0' cellspacing='0' class='section-columns columns-2'> <tbody> <tr> <td class='first columns-cell'> <div class='foot no-items section' id='footer-2-1'></div> </td> <td class='columns-cell'> <div class='foot no-items section' id='footer-2-2'></div> </td> </tr> </tbody> </table>  <div class='foot section' id='footer-3'><div class='widget Attribution' data-version='1' id='Attribution1'> <div class='widget-content' style='text-align: center;'> Powered by <a href='https://www.blogger.com' target='_blank'>Blogger</a>. </div> <div class='clear'></div> </div></div> </div> </div> <div class='footer-cap-bottom cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div> </footer>  </div> </div> <div class='content-cap-bottom cap-bottom'> <div class='cap-left'></div> <div class='cap-right'></div> </div> </div> </div> <script type='text/javascript'> window.setTimeout(function() { document.body.className = document.body.className.replace('loading', ''); }, 10); </script> <script type="text/javascript" src="https://www.blogger.com/static/v1/widgets/2725212210-widgets.js"></script> <script type='text/javascript'> window['__wavt'] = 'AOuZoY6C3zeMrjWZ_2PoEw6lPhjLKcYeKg:1740618965607';_WidgetManager._Init('//www.blogger.com/rearrange?blogID\x3d6264947694886887540','//www.righto.com/2016/06/','6264947694886887540'); _WidgetManager._SetDataContext([{'name': 'blog', 'data': {'blogId': '6264947694886887540', 'title': 'Ken Shirriff\x27s blog', 'url': 'http://www.righto.com/2016/06/', 'canonicalUrl': 'http://www.righto.com/2016/06/', 'homepageUrl': 'http://www.righto.com/', 'searchUrl': 'http://www.righto.com/search', 'canonicalHomepageUrl': 'http://www.righto.com/', 'blogspotFaviconUrl': 'http://www.righto.com/favicon.ico', 'bloggerUrl': 'https://www.blogger.com', 'hasCustomDomain': true, 'httpsEnabled': false, 'enabledCommentProfileImages': true, 'gPlusViewType': 'FILTERED_POSTMOD', 'adultContent': false, 'analyticsAccountNumber': 'UA-3782444-1', 'encoding': 'UTF-8', 'locale': 'en', 'localeUnderscoreDelimited': 'en', 'languageDirection': 'ltr', 'isPrivate': false, 'isMobile': false, 'isMobileRequest': false, 'mobileClass': '', 'isPrivateBlog': false, 'isDynamicViewsAvailable': true, 'feedLinks': '\x3clink rel\x3d\x22alternate\x22 type\x3d\x22application/atom+xml\x22 title\x3d\x22Ken Shirriff\x26#39;s blog - Atom\x22 href\x3d\x22http://www.righto.com/feeds/posts/default\x22 /\x3e\n\x3clink rel\x3d\x22alternate\x22 type\x3d\x22application/rss+xml\x22 title\x3d\x22Ken Shirriff\x26#39;s blog - RSS\x22 href\x3d\x22http://www.righto.com/feeds/posts/default?alt\x3drss\x22 /\x3e\n\x3clink rel\x3d\x22service.post\x22 type\x3d\x22application/atom+xml\x22 title\x3d\x22Ken Shirriff\x26#39;s blog - Atom\x22 href\x3d\x22https://www.blogger.com/feeds/6264947694886887540/posts/default\x22 /\x3e\n', 'meTag': '', 'adsenseHostId': 'ca-host-pub-1556223355139109', 'adsenseHasAds': false, 'adsenseAutoAds': false, 'boqCommentIframeForm': true, 'loginRedirectParam': '', 'view': '', 'dynamicViewsCommentsSrc': '//www.blogblog.com/dynamicviews/4224c15c4e7c9321/js/comments.js', 'dynamicViewsScriptSrc': '//www.blogblog.com/dynamicviews/74cfe181c1bbb7a1', 'plusOneApiSrc': 'https://apis.google.com/js/platform.js', 'disableGComments': true, 'interstitialAccepted': false, 'sharing': {'platforms': [{'name': 'Get link', 'key': 'link', 'shareMessage': 'Get link', 'target': ''}, {'name': 'Facebook', 'key': 'facebook', 'shareMessage': 'Share to Facebook', 'target': 'facebook'}, {'name': 'BlogThis!', 'key': 'blogThis', 'shareMessage': 'BlogThis!', 'target': 'blog'}, {'name': 'X', 'key': 'twitter', 'shareMessage': 'Share to X', 'target': 'twitter'}, {'name': 'Pinterest', 'key': 'pinterest', 'shareMessage': 'Share to Pinterest', 'target': 'pinterest'}, {'name': 'Email', 'key': 'email', 'shareMessage': 'Email', 'target': 'email'}], 'disableGooglePlus': true, 'googlePlusShareButtonWidth': 0, 'googlePlusBootstrap': '\x3cscript type\x3d\x22text/javascript\x22\x3ewindow.___gcfg \x3d {\x27lang\x27: \x27en\x27};\x3c/script\x3e'}, 'hasCustomJumpLinkMessage': false, 'jumpLinkMessage': 'Read more', 'pageType': 'archive', 'pageName': 'June 2016', 'pageTitle': 'Ken Shirriff\x27s blog: June 2016'}}, {'name': 'features', 'data': {}}, {'name': 'messages', 'data': {'edit': 'Edit', 'linkCopiedToClipboard': 'Link copied to clipboard!', 'ok': 'Ok', 'postLink': 'Post Link'}}, {'name': 'template', 'data': {'name': 'custom', 'localizedName': 'Custom', 'isResponsive': false, 'isAlternateRendering': false, 'isCustom': true}}, {'name': 'view', 'data': {'classic': {'name': 'classic', 'url': '?view\x3dclassic'}, 'flipcard': {'name': 'flipcard', 'url': '?view\x3dflipcard'}, 'magazine': {'name': 'magazine', 'url': '?view\x3dmagazine'}, 'mosaic': {'name': 'mosaic', 'url': '?view\x3dmosaic'}, 'sidebar': {'name': 'sidebar', 'url': '?view\x3dsidebar'}, 'snapshot': {'name': 'snapshot', 'url': '?view\x3dsnapshot'}, 'timeslide': {'name': 'timeslide', 'url': '?view\x3dtimeslide'}, 'isMobile': false, 'title': 'Ken Shirriff\x27s blog', 'description': 'Computer history, restoring vintage computers, IC reverse engineering, and whatever', 'url': 'http://www.righto.com/2016/06/', 'type': 'feed', 'isSingleItem': false, 'isMultipleItems': true, 'isError': false, 'isPage': false, 'isPost': false, 'isHomepage': false, 'isArchive': true, 'isLabelSearch': false, 'archive': {'year': 2016, 'month': 6, 'rangeMessage': 'Showing posts from June, 2016'}}}]); _WidgetManager._RegisterWidget('_HeaderView', new _WidgetInfo('Header1', 'header', document.getElementById('Header1'), {}, 'displayModeFull')); _WidgetManager._RegisterWidget('_BlogView', new _WidgetInfo('Blog1', 'main', document.getElementById('Blog1'), {'cmtInteractionsEnabled': false}, 'displayModeFull')); _WidgetManager._RegisterWidget('_HTMLView', new _WidgetInfo('HTML2', 'sidebar-right-1', document.getElementById('HTML2'), {}, 'displayModeFull')); _WidgetManager._RegisterWidget('_HTMLView', new _WidgetInfo('HTML3', 'sidebar-right-1', document.getElementById('HTML3'), {}, 'displayModeFull')); _WidgetManager._RegisterWidget('_PopularPostsView', new _WidgetInfo('PopularPosts1', 'sidebar-right-1', document.getElementById('PopularPosts1'), {}, 'displayModeFull')); _WidgetManager._RegisterWidget('_BlogSearchView', new _WidgetInfo('BlogSearch1', 'sidebar-right-1', document.getElementById('BlogSearch1'), {}, 'displayModeFull')); _WidgetManager._RegisterWidget('_LabelView', new _WidgetInfo('Label1', 'sidebar-right-1', document.getElementById('Label1'), {}, 'displayModeFull')); _WidgetManager._RegisterWidget('_BlogArchiveView', new _WidgetInfo('BlogArchive1', 'sidebar-right-1', document.getElementById('BlogArchive1'), {'languageDirection': 'ltr', 'loadingMessage': 'Loading\x26hellip;'}, 'displayModeFull')); _WidgetManager._RegisterWidget('_AttributionView', new _WidgetInfo('Attribution1', 'footer-3', document.getElementById('Attribution1'), {}, 'displayModeFull')); </script> </body> </html>