--- title: Linux on the Sega 32X. Who needs hardware... description: A developer ports Linux to the Sega 32X add-on, which features two Hitachi SH2 processors and only 320KB of RAM. The post covers the full journey: using a... canonical: https://daily.dev/posts/linux-on-the-sega-32x-who-needs-hardware-synchronization-primitives-anyway--hqibejcxm twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Linux on the Sega 32X. Who needs hardware synchronization primitives anyway? | daily.dev og:description: A developer ports Linux to the Sega 32X add-on, which features two Hitachi SH2 processors and only 320KB of RAM. The post covers the full journey: using a... og:url: https://daily.dev/posts/linux-on-the-sega-32x-who-needs-hardware-synchronization-primitives-anyway--hqibejcxm og:image: https://api.daily.dev/og/posts/hQIBejcXM.png og:image:alt: Linux on the Sega 32X. Who needs hardware synchronization primitives anyway? 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. # Linux on the Sega 32X. Who needs hardware synchronization primitives anyway? **[Hacker News](https://daily.dev/sources/hn)** · 13 min read · 0 upvotes · 0 comments ## Summary A developer ports Linux to the Sega 32X add-on, which features two Hitachi SH2 processors and only 320KB of RAM. The post covers the full journey: using a flash cart's ROM-as-RAM feature to get enough memory, fixing GCC internal compiler errors and register-clobbering bugs in the SH2 Linux port, writing an earlycon UART driver that routes through the 68000, and implementing a free-running timer driver. The most ambitious part is enabling SMP on hardware that lacks atomic synchronization primitives — solved by implementing Peterson's algorithm in software, using the 68000 as an IPI router, disabling caches to avoid stale values, and repurposing the SH2's hardware divider register as a CPU ID register. The result boots Linux with two CPUs on a 1994 game console add-on, albeit with poor performance due to bus contention. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do you implement SMP synchronization on hardware that lacks atomic read-modify-write primitives, like the Sega 32X's SH2 processors? Synchronization primitives such as cmpxchg can be implemented entirely in software using Peterson's algorithm, borrowing the approach from sparc32's kernel code. The SH2s in the Sega 32X lack a locked read-modify-write bus cycle, so flag and turn variables are placed in uncached memory to avoid stale cache reads, and inter-processor interrupts are routed through the Genesis's 68000 acting as a bus arbiter. Performance is poor but functional. _Developers wrestling with low-level concurrency primitives can find similar deep dives curated on daily.dev._ ### How can you get more usable RAM for a homebrew OS port on a console with very limited memory, like the Sega 32X's 256KB? Flash cartridges with special mapper configurations, such as those from Krikkz, can expose ROM as writeable RAM by toggling configuration bits, yielding 4MB of usable memory. A small portion, around 540KB, is reserved as ROM to hold the Linux and initramfs binary, while the rest becomes RAM that a loader copies the kernel into before jumping to it. _Anyone hacking around hardware memory constraints can track similar embedded bringup techniques on daily.dev._ ## Similar posts on daily.dev - [It’s Linux, On A Sega Megadrive](https://daily.dev/posts/it-s-linux-on-a-sega-megadrive-2dbyxcwkr) · Hackaday · 0 upvotes · 0 comments - [Someone made use of Linux's 68000 CPU compatibility by running it off an Atari Jaguar](https://daily.dev/posts/someone-made-use-of-linux-s-68000-cpu-compatibility-by-running-it-off-an-atari-jaguar-bs2kkrt12) · XDA Developers · 0 upvotes · 0 comments - [New Linux Patches Trying To Mainline Renesas SH7305 CPU Support](https://daily.dev/posts/new-linux-patches-trying-to-mainline-renesas-sh7305-cpu-support-tfzuo3b1g) · Phoronix · 0 upvotes · 0 comments - [Running Modern Linux On A 68008](https://daily.dev/posts/running-modern-linux-on-a-68008-ni9b7c7xe) · Hackaday · 5 upvotes · 0 comments - [GitHub - GrieferPig/esp32-s31-linux: Porting MMU Linux to ESP32-S31](https://daily.dev/posts/github---grieferpig-esp32-s31-linux-porting-mmu-linux-to-esp32-s31-o9nrg0dao) · Hacker News · 0 upvotes · 0 comments --- Tags: [#linux](https://daily.dev/tags/linux), [#embedded](https://daily.dev/tags/embedded) [View this post on daily.dev](https://daily.dev/posts/linux-on-the-sega-32x-who-needs-hardware-synchronization-primitives-anyway--hqibejcxm) ```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":"Linux on the Sega 32X. 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