Re: Some observations regarding the ongoing x86-32 CPU configuration cleanups

[H. Peter Anvin]

On November 9, 2026 4:29:08 AM PST, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>On Mon, Nov 09, 2026 at 10:34:54AM +0000, Luís Mendes wrote:
>> Hi everyone,
>> 
>> First of all i would like to say that i both admire and appreciate all
>> your hard work with this lovely OS. I do understand that maintaining
>> some systems can cause additional burden on maintenance, but there are
>> some aspects that i would like you to reconsider.
>> 
>> I am writing because I  believe that some aspects have not been taking
>> into consideration regarding the removal of the 80486 32-bit support
>> from the kernel, namely:
>> - There is this active Linux distribution:https://tinycorelinnux.net/
>> and the Damn Smal Linux DSL (https://damnsmalllinux.org).
>> - There are also these CPUs: https://www.vortex86.com/products/Vortex86EX
>> - There may be only a few vintage 486 systems still working, but there
>> are also other new x86 CPUs systems, especially in FPGAs like the
>> https://github.com/MiSTer-devel/ao486_MiSTer which is a 486SX core
>> that operates at 90MHz and can use up to 256MB RAM memory. There are
>> plans to update this CPU IP core to become a full 486DX core, by
>> adding a FPU unit to it and would turn this into a usable Desktop
>> system with tineycorelinux. There is a considerable retro-computing
>> community that utilizes the AO486 core on the MiSTer FPGA platform.
>> There is even a Voodoo 3dfx accelerator card:
>> https://github.com/victor-fisyuk/voodoo-fpga-public.
>> 
>> Overall i just want to inform you that some new x86 32-bit systems are
>> still being sold brand new and can be utilized with Linux. I would
>> like that you consider this with regard to how much 80486 support
>> should be removed from Linux.
>> 
>> Personally i do have plans to extend the AO486 core to have the FPU
>> and would like to be able to run a modern Linux on it. It would have
>> entertainment and educational applications. With tinycoreinux it can
>> have a usable desktop.
>
>I don't realistically see 486 support coming back -- the thing doesn't
>even have TSC. Getting rid of all the horrible (and completely untested)
>code for no-tsc alone was worth deleting 486 support for.
>
>The other option is you actually implementing RDTSC, CPUID (and possibly
>CMPXCHG8B) on your FPGA.  I'm sure that's actually a *LOT* simpler than
>doing i487 support.
>
>Just add whatever instructions are required to get the bare minimal
>32bit build working.

It would be more likely to get x87 emulation back!

Later i486's actually did have CPUID, and implementing TSC and CX8 (in a unicore system) is rather trivial.