CINXE.COM

<!DOCTYPE html> <html class="client-nojs vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-available" lang="en" dir="ltr"> <head> <meta charset="UTF-8"> <title>64b/66b encoding - Wikipedia</title> <script>(function(){var className="client-js vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-available";var cookie=document.cookie.match(/(?:^|; )enwikimwclientpreferences=([^;]+)/);if(cookie){cookie[1].split('%2C').forEach(function(pref){className=className.replace(new RegExp('(^| )'+pref.replace(/-clientpref-\w+$|[^\w-]+/g,'')+'-clientpref-\\w+( |$)'),'$1'+pref+'$2');});}document.documentElement.className=className;}());RLCONF={"wgBreakFrames":false,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy", "wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"f60a90a5-aa51-4181-bdc8-12817c0ea72b","wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"64b/66b_encoding","wgTitle":"64b/66b encoding","wgCurRevisionId":1257739951,"wgRevisionId":1257739951,"wgArticleId":7287059,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["Articles with short description","Short description matches Wikidata","Use mdy dates from September 2021","Use American English from March 2019","All Wikipedia articles written in American English","Articles lacking in-text citations from January 2017","All articles lacking in-text citations","All articles with vague or ambiguous time","Vague or ambiguous time from April 2021","Encodings","Line codes","Telecommunications standards"],"wgPageViewLanguage":"en", "wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"64b/66b_encoding","wgRelevantArticleId":7287059,"wgIsProbablyEditable":true,"wgRelevantPageIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":[],"wgNoticeProject":"wikipedia","wgCiteReferencePreviewsActive":false,"wgFlaggedRevsParams":{"tags":{"status":{"levels":1}}},"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgPopupsFlags":0,"wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr","pageVariantFallbacks":"en"},"wgMFDisplayWikibaseDescriptions":{"search":true,"watchlist":true,"tagline":false,"nearby":true},"wgWMESchemaEditAttemptStepOversample":false,"wgWMEPageLength":10000,"wgRelatedArticlesCompat":[],"wgCentralAuthMobileDomain":false,"wgEditSubmitButtonLabelPublish":true,"wgULSPosition":"interlanguage","wgULSisCompactLinksEnabled":false,"wgVector2022LanguageInHeader":true,"wgULSisLanguageSelectorEmpty":false,"wgWikibaseItemId":"Q2631891", "wgCheckUserClientHintsHeadersJsApi":["brands","architecture","bitness","fullVersionList","mobile","model","platform","platformVersion"],"GEHomepageSuggestedEditsEnableTopics":true,"wgGETopicsMatchModeEnabled":false,"wgGEStructuredTaskRejectionReasonTextInputEnabled":false,"wgGELevelingUpEnabledForUser":false};RLSTATE={"ext.globalCssJs.user.styles":"ready","site.styles":"ready","user.styles":"ready","ext.globalCssJs.user":"ready","user":"ready","user.options":"loading","ext.cite.styles":"ready","skins.vector.search.codex.styles":"ready","skins.vector.styles":"ready","skins.vector.icons":"ready","jquery.makeCollapsible.styles":"ready","ext.wikimediamessages.styles":"ready","ext.visualEditor.desktopArticleTarget.noscript":"ready","ext.uls.interlanguage":"ready","wikibase.client.init":"ready","ext.wikimediaBadges":"ready"};RLPAGEMODULES=["ext.cite.ux-enhancements","site","mediawiki.page.ready","jquery.makeCollapsible","mediawiki.toc","skins.vector.js","ext.centralNotice.geoIP", "ext.centralNotice.startUp","ext.gadget.ReferenceTooltips","ext.gadget.switcher","ext.urlShortener.toolbar","ext.centralauth.centralautologin","mmv.bootstrap","ext.popups","ext.visualEditor.desktopArticleTarget.init","ext.visualEditor.targetLoader","ext.echo.centralauth","ext.eventLogging","ext.wikimediaEvents","ext.navigationTiming","ext.uls.interface","ext.cx.eventlogging.campaigns","ext.cx.uls.quick.actions","wikibase.client.vector-2022","ext.checkUser.clientHints","ext.growthExperiments.SuggestedEditSession","wikibase.sidebar.tracking"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.impl(function(){return["user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); }];});});</script> <link rel="stylesheet" href="/w/load.php?lang=en&modules=ext.cite.styles%7Cext.uls.interlanguage%7Cext.visualEditor.desktopArticleTarget.noscript%7Cext.wikimediaBadges%7Cext.wikimediamessages.styles%7Cjquery.makeCollapsible.styles%7Cskins.vector.icons%2Cstyles%7Cskins.vector.search.codex.styles%7Cwikibase.client.init&only=styles&skin=vector-2022"> <script async="" src="/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector-2022"></script> <meta name="ResourceLoaderDynamicStyles" content=""> <link rel="stylesheet" href="/w/load.php?lang=en&modules=site.styles&only=styles&skin=vector-2022"> <meta name="generator" content="MediaWiki 1.44.0-wmf.4"> <meta name="referrer" content="origin"> <meta name="referrer" content="origin-when-cross-origin"> <meta name="robots" content="max-image-preview:standard"> <meta name="format-detection" content="telephone=no"> <meta name="viewport" content="width=1120"> <meta property="og:title" content="64b/66b encoding - Wikipedia"> <meta property="og:type" content="website"> <link rel="preconnect" href="//upload.wikimedia.org"> <link rel="alternate" media="only screen and (max-width: 640px)" href="//en.m.wikipedia.org/wiki/64b/66b_encoding"> <link rel="alternate" type="application/x-wiki" title="Edit this page" href="/w/index.php?title=64b/66b_encoding&action=edit"> <link rel="apple-touch-icon" href="/static/apple-touch/wikipedia.png"> <link rel="icon" href="/static/favicon/wikipedia.ico"> <link rel="search" type="application/opensearchdescription+xml" href="/w/rest.php/v1/search" title="Wikipedia (en)"> <link rel="EditURI" type="application/rsd+xml" href="//en.wikipedia.org/w/api.php?action=rsd"> <link rel="canonical" href="https://en.wikipedia.org/wiki/64b/66b_encoding"> <link rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en"> <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" href="/w/index.php?title=Special:RecentChanges&feed=atom"> <link rel="dns-prefetch" href="//meta.wikimedia.org" /> <link rel="dns-prefetch" href="//login.wikimedia.org"> </head> <body class="skin--responsive skin-vector skin-vector-search-vue mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject mw-editable page-64b_66b_encoding rootpage-64b_66b_encoding skin-vector-2022 action-view"><a class="mw-jump-link" href="#bodyContent">Jump to content</a> <div class="vector-header-container"> <header class="vector-header mw-header"> <div class="vector-header-start"> <nav class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-dropdown" class="vector-dropdown vector-main-menu-dropdown vector-button-flush-left vector-button-flush-right" > <input type="checkbox" id="vector-main-menu-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-main-menu-dropdown" class="vector-dropdown-checkbox " aria-label="Main menu" > <label id="vector-main-menu-dropdown-label" for="vector-main-menu-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-menu mw-ui-icon-wikimedia-menu"></span> <span class="vector-dropdown-label-text">Main menu</span> </label> <div class="vector-dropdown-content"> <div id="vector-main-menu-unpinned-container" class="vector-unpinned-container"> <div id="vector-main-menu" class="vector-main-menu vector-pinnable-element"> <div class="vector-pinnable-header vector-main-menu-pinnable-header vector-pinnable-header-unpinned" data-feature-name="main-menu-pinned" data-pinnable-element-id="vector-main-menu" data-pinned-container-id="vector-main-menu-pinned-container" data-unpinned-container-id="vector-main-menu-unpinned-container" > <div class="vector-pinnable-header-label">Main menu</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-main-menu.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-main-menu.unpin">hide</button> </div> <div id="p-navigation" class="vector-menu mw-portlet mw-portlet-navigation" > <div class="vector-menu-heading"> Navigation </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-mainpage-description" class="mw-list-item"><a href="/wiki/Main_Page" title="Visit the main page [z]" accesskey="z"><span>Main page</span></a></li><li id="n-contents" class="mw-list-item"><a href="/wiki/Wikipedia:Contents" title="Guides to browsing Wikipedia"><span>Contents</span></a></li><li id="n-currentevents" class="mw-list-item"><a href="/wiki/Portal:Current_events" title="Articles related to current events"><span>Current events</span></a></li><li id="n-randompage" class="mw-list-item"><a href="/wiki/Special:Random" title="Visit a randomly selected article [x]" accesskey="x"><span>Random article</span></a></li><li id="n-aboutsite" class="mw-list-item"><a href="/wiki/Wikipedia:About" title="Learn about Wikipedia and how it works"><span>About Wikipedia</span></a></li><li id="n-contactpage" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us" title="How to contact Wikipedia"><span>Contact us</span></a></li> </ul> </div> </div> <div id="p-interaction" class="vector-menu mw-portlet mw-portlet-interaction" > <div class="vector-menu-heading"> Contribute </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-help" class="mw-list-item"><a href="/wiki/Help:Contents" title="Guidance on how to use and edit Wikipedia"><span>Help</span></a></li><li id="n-introduction" class="mw-list-item"><a href="/wiki/Help:Introduction" title="Learn how to edit Wikipedia"><span>Learn to edit</span></a></li><li id="n-portal" class="mw-list-item"><a href="/wiki/Wikipedia:Community_portal" title="The hub for editors"><span>Community portal</span></a></li><li id="n-recentchanges" class="mw-list-item"><a href="/wiki/Special:RecentChanges" title="A list of recent changes to Wikipedia [r]" accesskey="r"><span>Recent changes</span></a></li><li id="n-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_upload_wizard" title="Add images or other media for use on Wikipedia"><span>Upload file</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> <a href="/wiki/Main_Page" class="mw-logo"> <img class="mw-logo-icon" src="/static/images/icons/wikipedia.png" alt="" aria-hidden="true" height="50" width="50"> <span class="mw-logo-container skin-invert"> <img class="mw-logo-wordmark" alt="Wikipedia" src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" style="width: 7.5em; height: 1.125em;"> <img class="mw-logo-tagline" alt="The Free Encyclopedia" src="/static/images/mobile/copyright/wikipedia-tagline-en.svg" width="117" height="13" style="width: 7.3125em; height: 0.8125em;"> </span> </a> </div> <div class="vector-header-end"> <div id="p-search" role="search" class="vector-search-box-vue vector-search-box-collapses vector-search-box-show-thumbnail vector-search-box-auto-expand-width vector-search-box"> <a href="/wiki/Special:Search" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only search-toggle" title="Search Wikipedia [f]" accesskey="f"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </a> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail cdx-typeahead-search--auto-expand-width"> <form action="/w/index.php" id="searchform" class="cdx-search-input cdx-search-input--has-end-button"> <div id="simpleSearch" class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia" aria-label="Search Wikipedia" autocapitalize="sentences" title="Search Wikipedia [f]" accesskey="f" id="searchInput" > <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <nav class="vector-user-links vector-user-links-wide" aria-label="Personal tools"> <div class="vector-user-links-main"> <div id="p-vector-user-menu-preferences" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-userpage" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-dropdown" class="vector-dropdown " title="Change the appearance of the page's font size, width, and color" > <input type="checkbox" id="vector-appearance-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-appearance-dropdown" class="vector-dropdown-checkbox " aria-label="Appearance" > <label id="vector-appearance-dropdown-label" for="vector-appearance-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-appearance mw-ui-icon-wikimedia-appearance"></span> <span class="vector-dropdown-label-text">Appearance</span> </label> <div class="vector-dropdown-content"> <div id="vector-appearance-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div id="p-vector-user-menu-notifications" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-overflow" class="vector-menu mw-portlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=64b%2F66b+encoding" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=64b%2F66b+encoding" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o" class=""><span>Log in</span></a> </li> </ul> </div> </div> </div> <div id="vector-user-links-dropdown" class="vector-dropdown vector-user-menu vector-button-flush-right vector-user-menu-logged-out" title="Log in and more options" > <input type="checkbox" id="vector-user-links-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-user-links-dropdown" class="vector-dropdown-checkbox " aria-label="Personal tools" > <label id="vector-user-links-dropdown-label" for="vector-user-links-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-ellipsis mw-ui-icon-wikimedia-ellipsis"></span> <span class="vector-dropdown-label-text">Personal tools</span> </label> <div class="vector-dropdown-content"> <div id="p-personal" class="vector-menu mw-portlet mw-portlet-personal user-links-collapsible-item" title="User menu" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport" class="user-links-collapsible-item mw-list-item"><a href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en"><span>Donate</span></a></li><li id="pt-createaccount" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:CreateAccount&returnto=64b%2F66b+encoding" title="You are encouraged to create an account and log in; however, it is not mandatory"><span class="vector-icon mw-ui-icon-userAdd mw-ui-icon-wikimedia-userAdd"></span> <span>Create account</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:UserLogin&returnto=64b%2F66b+encoding" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>Log in</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> Pages for logged out editors <a href="/wiki/Help:Introduction" aria-label="Learn more about editing"><span>learn more</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y"><span>Contributions</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n"><span>Talk</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="Contents" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Contents</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Function" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Function"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Function</span> </div> </a> <ul id="toc-Function-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Properties_and_application" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Properties_and_application"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Properties and application</span> </div> </a> <button aria-controls="toc-Properties_and_application-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Properties and application subsection</span> </button> <ul id="toc-Properties_and_application-sublist" class="vector-toc-list"> <li id="toc-Run_length" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Run_length"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Run length</span> </div> </a> <ul id="toc-Run_length-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-DC_balance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#DC_balance"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>DC balance</span> </div> </a> <ul id="toc-DC_balance-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Hamming_distance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Hamming_distance"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>Hamming distance</span> </div> </a> <ul id="toc-Hamming_distance-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Observations" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Observations"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4</span> <span>Observations</span> </div> </a> <ul id="toc-Observations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Variations" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Variations"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.5</span> <span>Variations</span> </div> </a> <ul id="toc-Variations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Successors" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Successors"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.6</span> <span>Successors</span> </div> </a> <ul id="toc-Successors-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Technologies_that_use_64b/66b_encoding" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Technologies_that_use_64b/66b_encoding"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Technologies that use 64b/66b encoding</span> </div> </a> <ul id="toc-Technologies_that_use_64b/66b_encoding-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Technologies_that_use_128b/1xxb_encoding" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Technologies_that_use_128b/1xxb_encoding"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Technologies that use 128b/1xxb encoding</span> </div> </a> <ul id="toc-Technologies_that_use_128b/1xxb_encoding-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Technologies_that_use_256b/257b_encoding" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Technologies_that_use_256b/257b_encoding"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Technologies that use 256b/257b encoding</span> </div> </a> <ul id="toc-Technologies_that_use_256b/257b_encoding-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">64b/66b encoding</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 3 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-3" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">3 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Codificaci%C3%B3_64b/66b" title="Codificació 64b/66b – Catalan" lang="ca" hreflang="ca" data-title="Codificació 64b/66b" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/64b66b-Code" title="64b66b-Code – German" lang="de" hreflang="de" data-title="64b66b-Code" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Codage_64b/66b" title="Codage 64b/66b – French" lang="fr" hreflang="fr" data-title="Codage 64b/66b" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q2631891#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/64b/66b_encoding" title="View the content page [c]" accesskey="c"><span>Article</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Talk:64b/66b_encoding" rel="discussion" title="Discuss improvements to the content page [t]" accesskey="t"><span>Talk</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="Change language variant" > <label id="vector-variants-dropdown-label" for="vector-variants-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">English</span> </label> <div class="vector-dropdown-content"> <div id="p-variants" class="vector-menu mw-portlet mw-portlet-variants emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> </div> </div> </nav> </div> <div id="right-navigation" class="vector-collapsible"> <nav aria-label="Views"> <div id="p-views" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-views" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-view" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/64b/66b_encoding"><span>Read</span></a></li><li id="ca-edit" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=64b/66b_encoding&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=64b/66b_encoding&action=history" title="Past revisions of this page [h]" accesskey="h"><span>View history</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-dropdown" class="vector-dropdown vector-page-tools-dropdown" > <input type="checkbox" id="vector-page-tools-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-tools-dropdown" class="vector-dropdown-checkbox " aria-label="Tools" > <label id="vector-page-tools-dropdown-label" for="vector-page-tools-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">Tools</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-tools-unpinned-container" class="vector-unpinned-container"> <div id="vector-page-tools" class="vector-page-tools vector-pinnable-element"> <div class="vector-pinnable-header vector-page-tools-pinnable-header vector-pinnable-header-unpinned" data-feature-name="page-tools-pinned" data-pinnable-element-id="vector-page-tools" data-pinned-container-id="vector-page-tools-pinned-container" data-unpinned-container-id="vector-page-tools-unpinned-container" > <div class="vector-pinnable-header-label">Tools</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">hide</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="More options" > <div class="vector-menu-heading"> Actions </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="selected vector-more-collapsible-item mw-list-item"><a href="/wiki/64b/66b_encoding"><span>Read</span></a></li><li id="ca-more-edit" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=64b/66b_encoding&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=64b/66b_encoding&action=history"><span>View history</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> General </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Special:WhatLinksHere/64b/66b_encoding" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j"><span>What links here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/64b/66b_encoding" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-specialpages" class="mw-list-item"><a href="/wiki/Special:SpecialPages" title="A list of all special pages [q]" accesskey="q"><span>Special pages</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=64b/66b_encoding&oldid=1257739951" title="Permanent link to this revision of this page"><span>Permanent link</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=64b/66b_encoding&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Special:CiteThisPage&page=64b%2F66b_encoding&id=1257739951&wpFormIdentifier=titleform" title="Information on how to cite this page"><span>Cite this page</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2F64b%2F66b_encoding"><span>Get shortened URL</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2F64b%2F66b_encoding"><span>Download QR code</span></a></li> </ul> </div> </div> <div id="p-coll-print_export" class="vector-menu mw-portlet mw-portlet-coll-print_export" > <div class="vector-menu-heading"> Print/export </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=Special:DownloadAsPdf&page=64b%2F66b_encoding&action=show-download-screen" title="Download this page as a PDF file"><span>Download as PDF</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=64b/66b_encoding&printable=yes" title="Printable version of this page [p]" accesskey="p"><span>Printable version</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q2631891" title="Structured data on this page hosted by Wikidata [g]" accesskey="g"><span>Wikidata item</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Line code used in Ethernet technologies</div> <p class="mw-empty-elt"> </p> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_footnotes_needed plainlinks metadata ambox ambox-style ambox-More_footnotes_needed" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Text_document_with_red_question_mark.svg/40px-Text_document_with_red_question_mark.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Text_document_with_red_question_mark.svg/60px-Text_document_with_red_question_mark.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Text_document_with_red_question_mark.svg/80px-Text_document_with_red_question_mark.svg.png 2x" data-file-width="48" data-file-height="48" /></span></span></div></td><td class="mbox-text"><div class="mbox-text-span">This article includes a list of <a href="/wiki/Wikipedia:Citing_sources#General_references" title="Wikipedia:Citing sources">general references</a>, but <b>it lacks sufficient corresponding <a href="/wiki/Wikipedia:Citing_sources#Inline_citations" title="Wikipedia:Citing sources">inline citations</a></b>.<span class="hide-when-compact"> Please help to <a href="/wiki/Wikipedia:WikiProject_Reliability" title="Wikipedia:WikiProject Reliability">improve</a> this article by <a href="/wiki/Wikipedia:When_to_cite" title="Wikipedia:When to cite">introducing</a> more precise citations.</span> <span class="date-container"><i>(<span class="date">January 2017</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p>In data networking and transmission, <b>64b/66b</b> is a <a href="/wiki/Line_code" title="Line code">line code</a> that transforms 64-<a href="/wiki/Bit" title="Bit">bit</a> data to 66-bit <a href="/wiki/Line_code" title="Line code">line code</a> to provide enough state changes to allow reasonable <a href="/wiki/Clock_recovery" title="Clock recovery">clock recovery</a> and alignment of the data stream at the receiver. It was defined by the <a href="/wiki/Institute_of_Electrical_and_Electronics_Engineers" title="Institute of Electrical and Electronics Engineers">IEEE</a> <a href="/wiki/IEEE_802.3" title="IEEE 802.3">802.3 working group</a> as part of the IEEE 802.3ae-2002 amendment which introduced 10 Gbit/s Ethernet. At the time 64b/66b was deployed, it allowed 10 Gb Ethernet to be transmitted with the same lasers used by <a href="/wiki/SONET" class="mw-redirect" title="SONET">SONET</a> <a href="/wiki/OC-192" class="mw-redirect" title="OC-192">OC-192</a>, rather than requiring the 12.5 Gbit/s lasers that were not expected<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Manual_of_Style/Dates_and_numbers#Chronological_items" title="Wikipedia:Manual of Style/Dates and numbers"><span title="The time period mentioned near this tag is ambiguous. (April 2021)">when?</span></a></i>]</sup> to be available for several years. </p><p>The <a href="/wiki/Protocol_overhead" class="mw-redirect" title="Protocol overhead">protocol overhead</a> of a coding scheme is the ratio of the number of raw payload bits to the number of raw payload bits plus the number of added coding bits. The overhead of 64b/66b encoding is 2 coding bits for every 64 payload bits or 3.125%. This is a considerable improvement on the 25% overhead of the previously-used <a href="/wiki/8b/10b_encoding" title="8b/10b encoding">8b/10b encoding</a> scheme, which added 2 coding bits to every 8 payload bits. </p><p>The overhead can be reduced further by doubling the payload size to produce the <b>128b/130b</b> encoding used by <a href="/wiki/PCIe" class="mw-redirect" title="PCIe">PCIe</a> 3.0. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Function">Function</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=1" title="Edit section: Function"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>As its scheme name suggests, 64 payload <a href="/wiki/Bit" title="Bit">bits</a> are encoded as a 66-bit entity. The 66-bit entity is made by prefixing one of two possible 2-bit preambles to the 64 payload bits. This 66-bit entity is now of two possible states. </p> <ul><li>If the preamble is 01<sub>2</sub>, the 64 payload bits are data.</li> <li>If the preamble is 10<sub>2</sub>, the 64 payload bits hold an 8-bit Type field and 56 bits of control information and/or data.</li></ul> <p>The preambles 00<sub>2</sub> and 11<sub>2</sub> are not used and indicate an error if seen. </p><p>The use of the 01<sub>2</sub> and 10<sub>2</sub> preambles guarantees a bit transition every 66 bits, which means that a continuous stream of 0s or 1s cannot be valid data. It also allows easier clock/timer synchronization, as a transition must be seen every 66 bits. </p><p>The 64-bit payload is then scrambled using a self-synchronous <a href="/wiki/Scrambler_(randomizer)" class="mw-redirect" title="Scrambler (randomizer)">scrambler</a> function. Scrambling is not intended to encrypt the data but to ensure that a relatively even distribution of 1s and 0s are found in the transmitted data. The scrambler cannot guarantee that output data will never have a long run-length of 0s or all 1s, or other undesirable properties in communications, but does allow strong statistical bounds to be put on the probability of such events. Practical designs will choose system parameters such that a bit-error due to long run-lengths is vanishingly unlikely. This method is different from the code-book based approach of <a href="/wiki/8b/10b_encoding" title="8b/10b encoding">8b/10b encoding</a>. </p><p>The encoding and scrambling are normally implemented entirely in hardware, with the scrambler using a <a href="/wiki/Linear-feedback_shift_register" title="Linear-feedback shift register">linear-feedback shift register</a>. Upper layers of the software stack need not be aware that the link layer is using these methods. </p> <div class="mw-heading mw-heading2"><h2 id="Properties_and_application">Properties and application</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=2" title="Edit section: Properties and application"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>64b/66b's design goals are clock recovery, stream alignment, DC balance, transition density and run length. 8b/10b encoding guarantees strict bounds on DC balance, transition density and run length, whereas 64b/66b provides statistical bounds on these properties. </p> <div class="mw-heading mw-heading3"><h3 id="Run_length">Run length</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=3" title="Edit section: Run length"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Most clock recovery circuits designed for SONET OC-192 and 64b/66b are specified to tolerate an 80-bit run length. Such a run cannot occur in 64b/66b because transitions are guaranteed at 66-bit intervals, and in fact long runs are very unlikely. Although it is theoretically possible for a random data pattern to align with the scrambler state and produce a long run of 65 zeroes or 65 ones, the probability of such an event is equal to flipping a <a href="/wiki/Fair_coin" title="Fair coin">fair coin</a> and having it come up in the same state 64 times in a row. At 10 Gigabits per second, the expected event rate of a 66-bit block with a 65-bit run-length, assuming random data, is 66×2<sup>64</sup>÷10<sup>10</sup>÷2 seconds, or about once every 1900 years. </p><p>The run length statistics may get worse if the data consists of specifically chosen patterns, instead of being random. An earlier scrambler used in <a href="/wiki/Packet_over_SONET/SDH" title="Packet over SONET/SDH">Packet over SONET/SDH</a> (<style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><a href="/wiki/RFC_(identifier)" class="mw-redirect" title="RFC (identifier)">RFC</a> <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc1619">1619</a> (1994)) had a short polynomial with only 7 bits of internal state which allowed a malicious attacker to create a <a href="/wiki/Denial-of-service_attack" title="Denial-of-service attack">Denial-of-service attack</a> by transmitting patterns in all 2<sup>7</sup>−1 states, one of which was guaranteed to de-synchronize the clock recovery circuits. This vulnerability was kept secret until the scrambler length was increased to 43 bits (<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/RFC_(identifier)" class="mw-redirect" title="RFC (identifier)">RFC</a> <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc2615">2615</a> (1999)) making it impossible for a malicious attacker to jam the system with a short sequence. </p><p>64b/66b avoided this vulnerability by using a scrambling polynomial with enough random internal state (58 bits) so that a dedicated attacker using a crafted Ethernet packet can only create a 64-bit run-length in the scrambler output once in about 29 years.<sup id="cite_ref-walker_1_0100_1-0" class="reference"><a href="#cite_note-walker_1_0100-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page / location: 11–13">: 11–13 </span></sup> This creates 66-bit blocks containing 65-bit runs at a rate similar to using random data. </p> <div class="mw-heading mw-heading3"><h3 id="DC_balance">DC balance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=4" title="Edit section: DC balance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The DC balance of 64b/66b is not absolutely bounded. However, it can be shown that the scrambler output closely approximates a sequence of random binary bits. Passing such a sequence through an AC-coupled circuit produces a <a href="/w/index.php?title=Baseline_wander&action=edit&redlink=1" class="new" title="Baseline wander (page does not exist)">baseline wander</a> noise that follows a <a href="/wiki/Gaussian_distribution" class="mw-redirect" title="Gaussian distribution">Gaussian distribution</a>, and the impact on the system error rate can be statistically quantified. In practice, a modest coupling capacitor value of 1 nF in a 100 Ω system is sufficient to guarantee that a DC drift of more than 2.5% will occur less often than once per 10<sup>22</sup> bits (about 31,700 years at 10 Gbit/s). [1]:15–16 </p> <div class="mw-heading mw-heading3"><h3 id="Hamming_distance">Hamming distance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=5" title="Edit section: Hamming distance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/10_Gigabit_Ethernet" title="10 Gigabit Ethernet">10 Gigabit Ethernet</a> has a strict charter requiring a Mean Time to False Packet Acceptance (MTTFPA) to be on the order of 1 billion years for a single operating link. To achieve this at normal bit error rates requires at least a 4-bit <a href="/wiki/Hamming_distance" title="Hamming distance">Hamming distance</a> protection for all packet data. In other words, all combinations of 3 randomly spaced bit-flips within a packet boundary must be detected and result in an invalidated packet. Several strategies were combined to achieve the 4-bit Hamming distance for 64b/66b packets: 1) strong type fields were chosen with 4-bit Hamming distance, 2) the scrambler polynomial was chosen to be compatible with the CRC-32 used for packet protection and 3) protocol violations adjacent to the packet boundaries are required to invalidate the packet. The combination of CRC-32 and the chosen scrambler polynomial were evaluated by exhaustively enumerating all 4-bit error patterns for all possible packet sizes with an optimized C program. </p> <div class="mw-heading mw-heading3"><h3 id="Observations">Observations</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=6" title="Edit section: Observations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The main contribution of 64b/66b is the observation that deterministic run length and transition density of 8b/10b are not always worth a 25% code overhead, and that solid robust systems could be designed using statistically bounded methods. At some point, practical risks, whether from <a href="/wiki/Mean_time_between_failures" title="Mean time between failures">MTBF</a> of components such as power supplies or from phenomena such as <a href="/wiki/Cosmic_ray#Effect_on_electronics" title="Cosmic ray">cosmic rays</a> or <a href="/wiki/Solar_flare#Hazards" title="Solar flare">solar flares</a>, dominate the reliability of both 8b/10b and 64b/66b systems. </p> <div class="mw-heading mw-heading3"><h3 id="Variations">Variations</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=7" title="Edit section: Variations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Interlaken_(networking)" title="Interlaken (networking)">Interlaken</a> protocol improves the DC balance further by trading off more coding bits. Its <a href="/w/index.php?title=64b/67b_encoding&action=edit&redlink=1" class="new" title="64b/67b encoding (page does not exist)">64b/67b encoding</a> extends 64b/66b with explicit DC balancing. This may be beneficial for some applications, such as using smaller on-chip coupling capacitors. </p><p><a href="/wiki/PCI_Express" title="PCI Express">PCI Express</a> 3.0 introduced 128b/130b encoding, which is similar to 64b/66b but has a payload of 128 bits instead of 64 bits, and uses a different scrambling polynomial: <i>x</i><sup>23</sup> + <i>x</i><sup>21</sup> + <i>x</i><sup>16</sup> + <i>x</i><sup>8</sup> + <i>x</i><sup>5</sup> + <i>x</i><sup>2</sup> + 1. It is also not self-synchronous and so requires explicit synchronization of seed values, in contrast with 64b/66b. </p><p><a href="/wiki/USB_3.1" class="mw-redirect" title="USB 3.1">USB 3.1</a> and <a href="/wiki/DisplayPort_2.0" class="mw-redirect" title="DisplayPort 2.0">DisplayPort 2.0</a> use 128b/132b encoding, which is identical to 64b/66b, but duplicates each of the preamble bits to reduce the risk of undetected errors there. </p> <div class="mw-heading mw-heading3"><h3 id="Successors">Successors</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=8" title="Edit section: Successors"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>For each {<i>n</i>}b/{<i>n</i>+2}b encoding, the symbol/data ratio is always below 1. With a ratio of 0.985 for 128b/130b encoding, there is no real margin for improvement. </p><p>The following approaches are available to further increase the data rate: </p> <dl><dt>Higher symbol rates combined with <a href="/wiki/Forward_error_correction" class="mw-redirect" title="Forward error correction">FEC</a></dt> <dd></dd></dl> <p>Very common are 512b/514b encodings combined with <a href="/wiki/Reed%E2%80%93Solomon_error_correction" title="Reed–Solomon error correction">Reed–Solomon error correction</a>. The following variants are often used: </p> <ul><li>RS(528,514,<span style="visibility:hidden;color:transparent;">0</span>7,10), adding 14 correction bits to the 512b/514b code word, allowing to correct up to <span style="visibility:hidden;color:transparent;">0</span>7 corrupted bits. Overhead is 3%, same as 64b/66b encoding</li> <li>RS(544,514,14,10), adding 30 correction bits to the 512b/514b code word, allowing to correct up to 15 corrupted bits. Overhead is 6%.</li></ul> <p>The FEC allows symbol error rates of 2.3 · 10<sup>−5</sup> or 2.2 · 10<sup>−4</sup> to achieve a <a href="/wiki/Bit_error_rate" title="Bit error rate">bit error rate</a> of less than 10<sup>−15</sup> in the transmitted data. </p> <dl><dt>Multi-level encoding combined with FEC</dt> <dd></dd></dl> <p>Further improvements are possible by switching from PAM-2 to <a href="/wiki/PAM-4" class="mw-redirect" title="PAM-4">PAM-4</a> or <a href="/wiki/Differential_signaling#2-wire" class="mw-redirect" title="Differential signaling">Ensemble</a> <a href="/wiki/Non-return-to-zero" title="Non-return-to-zero">NRZ</a> coding. </p> <dl><dt><a href="/wiki/Trellis_modulation" class="mw-redirect" title="Trellis modulation">Multi-level Trellis modulation</a> combined with FEC</dt> <dd></dd></dl> <div class="mw-heading mw-heading2"><h2 id="Technologies_that_use_64b/66b_encoding"><span id="Technologies_that_use_64b.2F66b_encoding"></span>Technologies that use 64b/66b encoding</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=9" title="Edit section: Technologies that use 64b/66b encoding"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 30em;"> <ul><li><a href="/wiki/100_Gigabit_Ethernet" title="100 Gigabit Ethernet">100 Gigabit Ethernet</a></li> <li><a href="/wiki/10G-EPON" title="10G-EPON">10G-EPON</a>, 10 Gbit/s Ethernet Passive Optical Network</li> <li><a href="/wiki/10_Gigabit_Ethernet" title="10 Gigabit Ethernet">10 Gigabit Ethernet</a> (most varieties)</li> <li><a href="/wiki/Aurora_(protocol)" title="Aurora (protocol)">Aurora</a>, from <a href="/wiki/Xilinx" title="Xilinx">Xilinx</a></li> <li><a href="/w/index.php?title=Camera_Link_HS&action=edit&redlink=1" class="new" title="Camera Link HS (page does not exist)">Camera Link HS</a></li> <li><a href="/wiki/Common_Public_Radio_Interface" title="Common Public Radio Interface">Common Public Radio Interface</a></li> <li><a href="/wiki/Fibre_Channel" title="Fibre Channel">Fibre Channel</a> 10GFC and 16GFC</li> <li><a href="/wiki/InfiniBand" title="InfiniBand">InfiniBand</a></li> <li><a href="/wiki/Thunderbolt_(interface)" title="Thunderbolt (interface)">Thunderbolt</a></li> <li><a href="/w/index.php?title=JESD204C&action=edit&redlink=1" class="new" title="JESD204C (page does not exist)">JESD204C</a></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="Technologies_that_use_128b/1xxb_encoding"><span id="Technologies_that_use_128b.2F1xxb_encoding"></span>Technologies that use 128b/1xxb encoding</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=10" title="Edit section: Technologies that use 128b/1xxb encoding"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1184024115"><div class="div-col" style="column-width: 30em;"> <ul><li><a href="/wiki/NVLink" title="NVLink">NVLink</a> 1.0</li> <li><a href="/wiki/PCI_Express#PCI_Express_3.0" title="PCI Express">PCIe 3.x</a></li> <li><a href="/wiki/PCI_Express#PCI_Express_4.0" title="PCI Express">PCIe 4.x</a></li> <li><a href="/wiki/PCI_Express#PCI_Express_5.0" title="PCI Express">PCIe 5.x</a></li> <li><a href="/wiki/SATA" title="SATA">SATA</a> 3.2</li> <li><a href="/wiki/Serial_Attached_SCSI" title="Serial Attached SCSI">SAS</a> 4</li> <li><a href="/wiki/USB_3.0" title="USB 3.0">USB 3.1 Gen2</a></li> <li><a href="/wiki/USB4" title="USB4">USB4</a></li> <li><a href="/wiki/DisplayPort#2.0" title="DisplayPort">DisplayPort 2.0</a></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="Technologies_that_use_256b/257b_encoding"><span id="Technologies_that_use_256b.2F257b_encoding"></span>Technologies that use 256b/257b encoding</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=11" title="Edit section: Technologies that use 256b/257b encoding"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1184024115"><div class="div-col" style="column-width: 30em;"> <ul><li><a href="/wiki/Fibre_Channel" title="Fibre Channel">Fibre Channel</a> 32GFC "Gen 6" and higher</li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=12" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-walker_1_0100-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-walker_1_0100_1-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFR.C._WalkerR._Dugan2000" class="citation web cs1"><a href="/wiki/R" title="R">R.C. Walker</a>; R. Dugan (January 18–20, 2000). <a rel="nofollow" class="external text" href="https://grouper.ieee.org/groups/802/3/10G_study/public/jan00/walker_1_0100.pdf">"64b/66b low-overhead coding proposal for serial links"</a> <span class="cs1-format">(PDF)</span>. IEEE 802.3 High Speed Study Group.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=64b%2F66b+low-overhead+coding+proposal+for+serial+links&rft.pub=IEEE+802.3+High+Speed+Study+Group&rft.date=2000-01-18%2F2000-01-20&rft.au=R.C.+Walker&rft.au=R.+Dugan&rft_id=https%3A%2F%2Fgrouper.ieee.org%2Fgroups%2F802%2F3%2F10G_study%2Fpublic%2Fjan00%2Fwalker_1_0100.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3A64b%2F66b+encoding" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=64b/66b_encoding&action=edit&section=13" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://grouper.ieee.org/groups/802/3/10G_study/public/jan00/walker_1_0100.pdf">64b/66b low-overhead coding proposal for serial links</a></li></ul> <dl><dd>Note that this is the original proposal to the IEEE, and some changes were made for the final, agreed standard. The circuit diagram for the 58-bit scrambling polynomial described in the proposal is identical to the one adopted in the standard. However, the proposal numbers the registers in reverse order such that the x<sup>58</sup>+x<sup>19</sup>+1 polynomial in the proposal is the same as the one labelled x<sup>58</sup>+x<sup>39</sup>+1 in the standard.</dd></dl> <ul><li><a rel="nofollow" class="external text" href="https://patents.google.com/patent/US6650638">US Patent/US6650638: Decoding method and decoder for 64b/66b coded packetized serial data</a></li> <li><a rel="nofollow" class="external text" href="https://patents.google.com/patent/US6718491">US Patent/US6718491: Coding method and coder for packetized serial data with low overhead</a></li> <li><a rel="nofollow" class="external text" href="https://patents.google.com/patent/US7055073">US Patent/US7055073: Coding method for coding packetized serial data with low overhead</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070310192256/http://gauss.ffii.org/PatentView/EP1133123">PatentView/EP1133123 Software Patent: 64b/66b decoding, for packetized serial data</a></li> <li><a rel="nofollow" class="external text" href="https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1556959">ERROR CORRECTION ON 64/66 BIT ENCODED LINKS</a></li> <li><a rel="nofollow" class="external text" href="http://www.iol.unh.edu/services/testing/10gec/training/10GbE_Cl49.pdf#search=%2264B%2F66B%20encoding%22">Introduction to 10 Gigabit 64b/66b (Clause 49)</a></li> <li><a rel="nofollow" class="external text" href="http://www.xilinx.com/support/documentation/application_notes/xapp775.pdf">A reference design by Xilinx on 64b/66b encoding and scrambling</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20100513022320/http://www.xilinx.com/products/ipcenter/aurora64b66b.htm">Aurora 64B66B IP core using 64b/66b encoding</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li dd:first-child::before,.mw-parser-output .hlist li dt:first-child::before,.mw-parser-output .hlist li li:first-child::before{content:" (";font-weight:normal}.mw-parser-output .hlist dd dd:last-child::after,.mw-parser-output .hlist dd dt:last-child::after,.mw-parser-output .hlist dd li:last-child::after,.mw-parser-output .hlist dt dd:last-child::after,.mw-parser-output .hlist dt dt:last-child::after,.mw-parser-output .hlist dt li:last-child::after,.mw-parser-output .hlist li dd:last-child::after,.mw-parser-output .hlist li dt:last-child::after,.mw-parser-output .hlist li li:last-child::after{content:")";font-weight:normal}.mw-parser-output .hlist ol{counter-reset:listitem}.mw-parser-output .hlist ol>li{counter-increment:listitem}.mw-parser-output .hlist ol>li::before{content:" "counter(listitem)"\a0 "}.mw-parser-output .hlist dd ol>li:first-child::before,.mw-parser-output .hlist dt ol>li:first-child::before,.mw-parser-output .hlist li ol>li:first-child::before{content:" ("counter(listitem)"\a0 "}</style><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output .navbox-list-with-group{text-align:left;border-left-width:2px;border-left-style:solid}.mw-parser-output tr+tr>.navbox-abovebelow,.mw-parser-output tr+tr>.navbox-group,.mw-parser-output tr+tr>.navbox-image,.mw-parser-output tr+tr>.navbox-list{border-top:2px solid #fdfdfd}.mw-parser-output .navbox-title{background-color:#ccf}.mw-parser-output .navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Line_coding_(digital_baseband_transmission)" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Bit-encoding" title="Template:Bit-encoding"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Bit-encoding" title="Template talk:Bit-encoding"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Bit-encoding" title="Special:EditPage/Template:Bit-encoding"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Line_coding_(digital_baseband_transmission)" style="font-size:114%;margin:0 4em"><a href="/wiki/Line_coding" class="mw-redirect" title="Line coding">Line coding</a> (digital baseband transmission)</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Main articles</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Unipolar_encoding" title="Unipolar encoding">Unipolar encoding</a></li> <li><a href="/wiki/Bipolar_encoding" title="Bipolar encoding">Bipolar encoding</a></li> <li><a href="/wiki/On%E2%80%93off_keying" title="On–off keying">On–off keying</a></li> <li><a href="/wiki/Mark_and_space" title="Mark and space">Mark and space</a></li></ul> </div></td><td class="noviewer navbox-image" rowspan="4" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/File:Digital_signal_encoding_formats-en.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/95/Digital_signal_encoding_formats-en.svg/240px-Digital_signal_encoding_formats-en.svg.png" decoding="async" width="240" height="206" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/95/Digital_signal_encoding_formats-en.svg/360px-Digital_signal_encoding_formats-en.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/95/Digital_signal_encoding_formats-en.svg/480px-Digital_signal_encoding_formats-en.svg.png 2x" data-file-width="586" data-file-height="504" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Basic <a href="/wiki/Line_code" title="Line code">line codes</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Return-to-zero" title="Return-to-zero">Return to zero (RZ)</a></li> <li><a href="/wiki/Non-return-to-zero#Non-return-to-zero_level" title="Non-return-to-zero">Non-return-to-zero, level (NRZ/NRZ-L)</a></li> <li><a href="/wiki/Non-return-to-zero#Non-return-to-zero_inverted" title="Non-return-to-zero">Non-return-to-zero, inverted (NRZ-I)</a></li> <li><a href="/wiki/Non-return-to-zero#Non-return-to-zero_space" title="Non-return-to-zero">Non-return-to-zero, space (NRZ-S)</a></li> <li><a href="/wiki/Manchester_code" title="Manchester code">Manchester</a></li> <li><a href="/wiki/Differential_Manchester_encoding" title="Differential Manchester encoding">Differential Manchester/biphase (Bi-φ)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Extended line codes</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Conditioned_diphase" class="mw-redirect" title="Conditioned diphase">Conditioned diphase</a></li> <li><a href="/wiki/4B3T" title="4B3T">4B3T</a></li> <li><a href="/wiki/4B5B" title="4B5B">4B5B</a></li> <li><a href="/wiki/2B1Q" title="2B1Q">2B1Q</a></li> <li><a href="/wiki/Bipolar_encoding#Alternate_mark_inversion" title="Bipolar encoding">Alternate mark inversion</a></li> <li><a href="/wiki/Modified_AMI_code" title="Modified AMI code">Modified AMI code</a></li> <li><a href="/wiki/Coded_mark_inversion" title="Coded mark inversion">Coded mark inversion</a></li> <li><a href="/wiki/MLT-3_encoding" title="MLT-3 encoding">MLT-3 encoding</a></li> <li><a href="/wiki/Hybrid_ternary_code" title="Hybrid ternary code">Hybrid ternary code</a></li> <li><a href="/wiki/6b/8b_encoding" title="6b/8b encoding">6b/8b encoding</a></li> <li><a href="/wiki/8b/10b_encoding" title="8b/10b encoding">8b/10b encoding</a></li> <li><a class="mw-selflink selflink">64b/66b encoding</a></li> <li><a href="/wiki/Eight-to-fourteen_modulation" title="Eight-to-fourteen modulation">Eight-to-fourteen modulation</a></li> <li><a href="/wiki/Delay_encoding" class="mw-redirect" title="Delay encoding">Delay/Miller encoding</a></li> <li><a href="/wiki/TC-PAM" title="TC-PAM">TC-PAM</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Optical line codes</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Carrier-suppressed_return-to-zero" class="mw-redirect" title="Carrier-suppressed return-to-zero">Carrier-suppressed return-to-zero</a></li> <li><a href="/wiki/Alternate-phase_return-to-zero" class="mw-redirect" title="Alternate-phase return-to-zero">Alternate-phase return-to-zero</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow hlist" colspan="3"><div> <ul><li><i>See also:</i> <a href="/wiki/Baseband" title="Baseband">Baseband</a></li> <li><a href="/wiki/Baud" title="Baud">Baud</a></li> <li><a href="/wiki/Bit_rate" title="Bit rate">Bit rate</a></li> <li><a href="/wiki/Digital_signal" title="Digital signal">Digital signal</a></li> <li><a href="/wiki/Digital_transmission" class="mw-redirect" title="Digital transmission">Digital transmission</a></li> <li><a href="/wiki/Ethernet_physical_layer" title="Ethernet physical layer">Ethernet physical layer</a></li> <li><a href="/wiki/Modulation#Pulse_modulation_methods" title="Modulation">Pulse modulation methods</a></li> <li><a href="/wiki/Pulse-amplitude_modulation" title="Pulse-amplitude modulation">Pulse-amplitude modulation</a> (PAM)</li> <li><a href="/wiki/Pulse-code_modulation" title="Pulse-code modulation">Pulse-code modulation</a> (PCM)</li> <li><a href="/wiki/Serial_communication" title="Serial communication">Serial communication</a></li> <li><a href="/wiki/Category:Line_codes" title="Category:Line codes">Category:Line codes</a></li></ul> </div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=64b/66b_encoding&oldid=1257739951">https://en.wikipedia.org/w/index.php?title=64b/66b_encoding&oldid=1257739951</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Encodings" title="Category:Encodings">Encodings</a></li><li><a href="/wiki/Category:Line_codes" title="Category:Line codes">Line codes</a></li><li><a href="/wiki/Category:Telecommunications_standards" title="Category:Telecommunications standards">Telecommunications standards</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li><li><a href="/wiki/Category:Use_mdy_dates_from_September_2021" title="Category:Use mdy dates from September 2021">Use mdy dates from September 2021</a></li><li><a href="/wiki/Category:Use_American_English_from_March_2019" title="Category:Use American English from March 2019">Use American English from March 2019</a></li><li><a href="/wiki/Category:All_Wikipedia_articles_written_in_American_English" title="Category:All Wikipedia articles written in American English">All Wikipedia articles written in American English</a></li><li><a href="/wiki/Category:Articles_lacking_in-text_citations_from_January_2017" title="Category:Articles lacking in-text citations from January 2017">Articles lacking in-text citations from January 2017</a></li><li><a href="/wiki/Category:All_articles_lacking_in-text_citations" title="Category:All articles lacking in-text citations">All articles lacking in-text citations</a></li><li><a href="/wiki/Category:All_articles_with_vague_or_ambiguous_time" title="Category:All articles with vague or ambiguous time">All articles with vague or ambiguous time</a></li><li><a href="/wiki/Category:Vague_or_ambiguous_time_from_April_2021" title="Category:Vague or ambiguous time from April 2021">Vague or ambiguous time from April 2021</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 16 November 2024, at 11:48<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. By using this site, you agree to the <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Terms_of_Use" class="extiw" title="foundation:Special:MyLanguage/Policy:Terms of Use">Terms of Use</a> and <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy" class="extiw" title="foundation:Special:MyLanguage/Policy:Privacy policy">Privacy Policy</a>. Wikipedia® is a registered trademark of the <a rel="nofollow" class="external text" href="https://wikimediafoundation.org/">Wikimedia Foundation, Inc.</a>, a non-profit organization.</li> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimers"><a href="/wiki/Wikipedia:General_disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-wm-codeofconduct"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct">Code of Conduct</a></li> <li id="footer-places-developers"><a href="https://developer.wikimedia.org">Developers</a></li> <li id="footer-places-statslink"><a href="https://stats.wikimedia.org/#/en.wikipedia.org">Statistics</a></li> <li id="footer-places-cookiestatement"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement">Cookie statement</a></li> <li id="footer-places-mobileview"><a href="//en.m.wikipedia.org/w/index.php?title=64b/66b_encoding&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://wikimediafoundation.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/static/images/footer/wikimedia-button.svg" width="84" height="29" alt="Wikimedia Foundation" loading="lazy"></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/w/resources/assets/poweredby_mediawiki.svg" alt="Powered by MediaWiki" width="88" height="31" loading="lazy"></a></li> </ul> </footer> </div> </div> </div> <div class="vector-settings" id="p-dock-bottom"> <ul></ul> </div><script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgHostname":"mw-web.codfw.main-f69cdc8f6-phpnv","wgBackendResponseTime":149,"wgPageParseReport":{"limitreport":{"cputime":"0.380","walltime":"0.496","ppvisitednodes":{"value":1655,"limit":1000000},"postexpandincludesize":{"value":24674,"limit":2097152},"templateargumentsize":{"value":1985,"limit":2097152},"expansiondepth":{"value":16,"limit":100},"expensivefunctioncount":{"value":5,"limit":500},"unstrip-depth":{"value":1,"limit":20},"unstrip-size":{"value":20249,"limit":5000000},"entityaccesscount":{"value":0,"limit":400},"timingprofile":["100.00% 438.022 1 -total"," 20.01% 87.660 1 Template:Bit-encoding"," 19.47% 85.292 1 Template:Navbox"," 17.28% 75.672 1 Template:More_footnotes"," 16.36% 71.665 1 Template:Short_description"," 15.89% 69.593 1 Template:Ambox"," 15.62% 68.417 1 Template:Reflist"," 12.66% 55.450 1 Template:Cite_web"," 9.80% 42.924 2 Template:Pagetype"," 9.13% 39.986 2 Template:IETF_RFC"]},"scribunto":{"limitreport-timeusage":{"value":"0.229","limit":"10.000"},"limitreport-memusage":{"value":4645786,"limit":52428800}},"cachereport":{"origin":"mw-api-int.codfw.main-849f99967d-5wjxb","timestamp":"20241123101103","ttl":2592000,"transientcontent":false}}});});</script> <script type="application/ld+json">{"@context":"https:\/\/schema.org","@type":"Article","name":"64b\/66b encoding","url":"https:\/\/en.wikipedia.org\/wiki\/64b\/66b_encoding","sameAs":"http:\/\/www.wikidata.org\/entity\/Q2631891","mainEntity":"http:\/\/www.wikidata.org\/entity\/Q2631891","author":{"@type":"Organization","name":"Contributors to Wikimedia projects"},"publisher":{"@type":"Organization","name":"Wikimedia Foundation, Inc.","logo":{"@type":"ImageObject","url":"https:\/\/www.wikimedia.org\/static\/images\/wmf-hor-googpub.png"}},"datePublished":"2006-10-04T15:49:24Z","dateModified":"2024-11-16T11:48:10Z","headline":"line code used in Ethernet technologies"}</script> </body> </html>