--- title: Your CPU still boots up pretending to be a 1978 Intel... description: Every x86 CPU, whether Intel or AMD, still boots into 16-bit real mode designed for the 1978 Intel 8086 before switching to protected and long mode. The reset... canonical: https://daily.dev/posts/your-cpu-still-boots-up-pretending-to-be-a-1978-intel-chip-and-intel-gave-up-on-removing-it-yoaapy56i twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Your CPU still boots up pretending to be a 1978 Intel chip, and Intel gave up on removing it | daily.dev og:description: Every x86 CPU, whether Intel or AMD, still boots into 16-bit real mode designed for the 1978 Intel 8086 before switching to protected and long mode. The reset... og:url: https://daily.dev/posts/your-cpu-still-boots-up-pretending-to-be-a-1978-intel-chip-and-intel-gave-up-on-removing-it-yoaapy56i og:image: https://api.daily.dev/og/posts/YoaaPY56i.png og:image:alt: Your CPU still boots up pretending to be a 1978 Intel chip, and Intel gave up on removing it og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Your CPU still boots up pretending to be a 1978 Intel chip, and Intel gave up on removing it **[XDA Developers](https://daily.dev/sources/xda-developers)** · 6 min read · 2 upvotes · 0 comments ## Summary Every x86 CPU, whether Intel or AMD, still boots into 16-bit real mode designed for the 1978 Intel 8086 before switching to protected and long mode. The reset vector, SIPI-based core wake-up, and 16-bit trampoline code in Linux and Windows all trace back to this legacy. Intel proposed X86S in 2023 to eliminate these legacy modes but abandoned the initiative in December 2024 after forming an advisory group with AMD, giving no detailed explanation. Separately, x86 expert Christian Ludloff disclosed in September 2026 that an unnamed manufacturer has reportedly shipped a PM64-only, PML5-only chip supporting FRED and APX at scale for over a year, though the vendor remains unidentified and unconfirmed. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why do modern x86 CPUs still boot into 16-bit real mode like an Intel 8086? Both Intel and AMD CPUs reset their control register CR0 to 60000010h at power-on, which disables protection and paging and puts the processor in the same real mode used by the 1978 Intel 8086. Firmware such as EDK2's UEFI reset vector still begins execution at physical address FFFF0h before switching to 32-bit protected mode and then 64-bit long mode, and Linux and Windows still ship 16-bit trampoline code to bring up additional CPU cores via SIPI. _Developers digging into boot internals and firmware quirks can follow x86 architecture explainers like this on daily.dev._ ### What happened to Intel's X86S initiative to remove legacy x86 modes? Intel proposed X86S in 2023 to eliminate legacy modes including real mode, 16-bit addressing, and SIPI-based core startup, arguing they served little purpose beyond bootstrapping into 64-bit mode. In December 2024 Intel confirmed to Tom's Hardware that it had abandoned X86S shortly after forming the x86 Ecosystem Advisory Group with AMD, without giving a detailed explanation; the group's first-year initiatives (FRED, AVX10, ACE, ChkTag) did not address removing real mode. _Those tracking x86 architecture direction can keep up with proposals like X86S being dropped via daily.dev._ ### Has any company actually shipped a 64-bit-only x86 chip without legacy real mode or compatibility mode? X86 expert Christian Ludloff, who runs Sandpile, disclosed on September 7, 2026 that he had been asked to document an unnamed company's PM64-only, PML5-only processor supporting FRED and APX, which had reportedly been used at scale for over a year with no legacy or compatibility mode. The manufacturer remains unidentified, with no public vendor documentation; Phoronix speculated about candidates like Zhaoxin, Hygon, or RosaicLabs, though none has been confirmed. _Engineers curious about emerging 64-bit-only x86 designs can track developments like this through daily.dev._ ## Similar posts on daily.dev - [Mysterious x86 CPU Already Has APX, x86S Where Intel Left Off For Legacy-Free x86](https://daily.dev/posts/mysterious-x86-cpu-already-has-apx-x86s-where-intel-left-off-for-legacy-free-x86-sjiimmxsz) · Phoronix · 0 upvotes · 0 comments - [Your PC still has a keyboard controller interface from 1984, and Linux keeps it as its second way to reboot](https://daily.dev/posts/your-pc-still-has-a-keyboard-controller-interface-from-1984-and-linux-keeps-it-as-its-second-way-to-amcdjxy9o) · XDA Developers · 0 upvotes · 0 comments - [The forgetful CPU \(Linux on M4\)](https://daily.dev/posts/the-forgetful-cpu-linux-on-m4--igqauax00) · Lobsters · 1 upvotes · 0 comments - [Small Things Retro](https://daily.dev/posts/small-things-retro-yps3c9exj) · Hacker News · 0 upvotes · 0 comments --- Tags: [#linux](https://daily.dev/tags/linux), [#hardware](https://daily.dev/tags/hardware), [#intel](https://daily.dev/tags/intel), [#amd](https://daily.dev/tags/amd) [View this post on daily.dev](https://daily.dev/posts/your-cpu-still-boots-up-pretending-to-be-a-1978-intel-chip-and-intel-gave-up-on-removing-it-yoaapy56i) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Your CPU still boots up pretending to be a 1978 Intel chip, and Intel gave up on removing it","url":"https://daily.dev/posts/your-cpu-still-boots-up-pretending-to-be-a-1978-intel-chip-and-intel-gave-up-on-removing-it-yoaapy56i","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/your-cpu-still-boots-up-pretending-to-be-a-1978-intel-chip-and-intel-gave-up-on-removing-it-yoaapy56i"},"datePublished":"2026-10-13T11:03:26.702Z","dateModified":"2026-10-13T12:23:40.763Z","description":"Every x86 CPU, whether Intel or AMD, still boots into 16-bit real mode designed for the 1978 Intel 8086 before switching to protected and long mode. 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Firmware such as EDK2's UEFI reset vector still begins execution at physical address FFFF0h before switching to 32-bit protected mode and then 64-bit long mode, and Linux and Windows still ship 16-bit trampoline code to bring up additional CPU cores via SIPI. Developers digging into boot internals and firmware quirks can follow x86 architecture explainers like this on daily.dev."}},{"@type":"Question","name":"What happened to Intel's X86S initiative to remove legacy x86 modes?","acceptedAnswer":{"@type":"Answer","text":"Intel proposed X86S in 2023 to eliminate legacy modes including real mode, 16-bit addressing, and SIPI-based core startup, arguing they served little purpose beyond bootstrapping into 64-bit mode. In December 2024 Intel confirmed to Tom's Hardware that it had abandoned X86S shortly after forming the x86 Ecosystem Advisory Group with AMD, without giving a detailed explanation; the group's first-year initiatives (FRED, AVX10, ACE, ChkTag) did not address removing real mode. Those tracking x86 architecture direction can keep up with proposals like X86S being dropped via daily.dev."}},{"@type":"Question","name":"Has any company actually shipped a 64-bit-only x86 chip without legacy real mode or compatibility mode?","acceptedAnswer":{"@type":"Answer","text":"X86 expert Christian Ludloff, who runs Sandpile, disclosed on September 7, 2026 that he had been asked to document an unnamed company's PM64-only, PML5-only processor supporting FRED and APX, which had reportedly been used at scale for over a year with no legacy or compatibility mode. The manufacturer remains unidentified, with no public vendor documentation; Phoronix speculated about candidates like Zhaoxin, Hygon, or RosaicLabs, though none has been confirmed. Engineers curious about emerging 64-bit-only x86 designs can track developments like this through daily.dev."}}]} ```