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Comment by magnat | Hacker News Reader

> Currently, it's not possible to run gray386linux on i486 machines (but it's possible to run gray386linux on Cyrix 486DLC and similar CPUs)

What's the cause? Incompatible/missing peripheral or some breaking changes in instruction set?

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Hi. I don't know for now. There is ton's of issues while switching to protected mode (ipxe for example: https://github.com/ipxe/ipxe/commit/bc35b24e3ebd2996b2484b7f...). It just stuck when I select it from PXE menu and I didn't debugged it further. Maybe someone can figure it out and send patches or advices.

Also it's not my goal to run gray386linux on i486 machines because I have another distribution: gray486linux, which aims specially to systems with 486 CPUs.

But what about folks who want to give their 386DX system a speed boost with RapidCAD? Will they have to re-install their OS? :) https://www.youtube.com/watch?v=UM4NPh5qg8Y

But seriously this stuff is very subtle. An issue (probably different) from a HN thread on similar matters: https://news.ycombinator.com/item?id=30801836

snort

The RapidCAD is pretty amusing since it’s literally just a castrated 486 (no L1! Eek!)

The Cyril gray top FastMath FPU is the best bet for an upgrade and still being a real 386 (I’m hunting for one for mine ) - https://www.vogons.org/viewtopic.php?t=65991

This hack might be a cause: https://github.com/marmolak/gray386linux/commit/81f9adb4656f...

Maybe and maybe another hacks and also not compiled support for 486 cpus. This hack is invoked only on CPUs, which doesn't support cmpxchg instruction. For example, 486 DLC from Cyrix is basically 386 with i486 instruction set but I'm not able to boot linux for 486 machines. https://en.wikipedia.org/wiki/Cyrix_Cx486DLC But gray386 runs perfectly on 486 DLC without hack involved.

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