DOS ain't dead

We talked about Linux dropping 80386 support, a few years ago. Now, 80486 got on the chopping board. Still, Linux keeps the support for Pentium and higher 32-bit x86 CPUs.

"More than 36 years after the release of the 486 and 18 years after Intel stopped making them, leaders of the Linux kernel believe the project can improve itself by leaving i486 support behind. Ingo Molnar, quoting Linus Torvalds regarding "zero real reason for anybody to waste one second" on 486 support, submitted a patch series to the 6.15 kernel that updates its minimum support features. Those requirements now include TSC (Time Stamp Counter) and CX8 (i.e., "fixed" CMPXCH8B, its own whole thing), features that the 486 lacks (as do some early non-Pentium 586 processors)."

https://arstechnica.com/gadgets/2025/05/linux-to-e...r-1989s-hottest-chip-the-486-with-next-release/

Linux 6.14 will be the last with 80486 support.

> https://arstechnica.com/gadgets/2025/05/linux-to-e...r-1989s-hottest-chip-the-486-with-next-release/
>
> Linux 6.14 will be the last with 80486 support.

I wonder how affected the early Vortex CPUs are. Mind you, they’re usually targeted at DOS and Windows 9x & XP.

> I wonder how affected the early Vortex CPUs are. Mind you, they’re
> usually targeted at DOS and Windows 9x & XP.

Wikipedia says that Vortex86 (even the first one) implements both CX8 and TSC, so it should be fine.

> > I wonder how affected the early Vortex CPUs are. Mind you, they’re
> > usually targeted at DOS and Windows 9x & XP.
>
> Wikipedia says that Vortex86 (even the first one) implements both CX8 and
> TSC, so it should be fine.

Does it have an x87 included? I think I read somewhere else that Linux dropping 486 support will remove the x87 emulation as well because Intel 586s all had an integrated x87.

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l

> Does it have an x87 included? I think I read somewhere else that Linux
> dropping 486 support will remove the x87 emulation as well because Intel
> 586s all had an integrated x87.

Depends on the model. Most do have, except for Vortex86SX and some very early models.

I though 486 was dropped many years ago but maybe I mixed it with Debian distro support that AFAIK needs at least 686 now. And I think most of distros are x64-only now so one may still compile 586 kernel but would be coupled with very few distros that still supports x86-32...

Vortex CPU also came in my mind. It depends how smart they did CPU detection. I think vortex has CPUID 4xx and if new kernel refuse anything <500 then vortex would have problem...

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DOS gives me freedom to unlimited HW access.

> I though 486 was dropped many years ago but maybe I mixed it with Debian
> distro support that AFAIK needs at least 686 now. And I think most of
> distros are x64-only now so one may still compile 586 kernel but would be
> coupled with very few distros that still supports x86-32...

Yes. Most distros are i686+ nowadays. If they even suport x86-32. There a few exceptions though. Gentoo has both i486 and i686+ versions. Slackware (32-bit) is by default i586 with some packages being i686.

Some distros that still support x86-32:
* Slackware
* Void Linux
* Gentoo
* Alpine Linux
* Antix
* MX Linux
* Q4OS
* Puppy Linux
* Damn Small Linux 2024
* Porteus
* Elive
* SparkyLinux (only minimal-cli and minimal-gui)
* Debian (but to be phased out in the future)