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SubjectRe: New Cyrix patch for 2.0.33
Hi Phil,

On Tue, 26 May 1998, Phil's Kernel Account wrote:

> On Tue, 26 May 1998, Mike Jagdis wrote:
>
> #Nah. If the cpuid failed you can't have a Pentium II so you can't
> #have a BX chip set. Don't waste your time - you can bet your life
> #that if/when Intel release a socket 7 BX-ish chip set or Cyrix
> #release a slot 2 CPU they will have changed things in ways you
> #haven't predicted :-).
>
> You're forgetting something; two days to AMD K6-3D. AMD's Slot1 entry. I'm
> taking the chance that it MIGHT not have cpuid enabled by default for some
> bizzare reason. NEVER assume things like that; the manufacturers will
> usually do the exact opposite. ;) And if Intel even looks at Socket7
> again, I think I'll wet myself. They're so intent on proprietarizing every
> little thing they do, I seriously doubt they're even looking back. If
> anything, they're probably screaming and yelling "we should have
> proprietarized socket7! now we can't exploit it any more!!" *smirk* :)

If more manufacturers start using ports 0x22 and 0x23, the we are really
in for trouble, unless we are certain that we are dealing with a Cyrix.
Cyrix assures that the port access won't generate external I/O for writes
(if done correctly, of course), but first we need to know that it IS a
Cyrix, which is a problem for CPUs with the cpuid off by default.

So it would be possible to have a BX-Cyrix(w/ cpuid) combo, but not a
Cyrix w/o cpuid enabled and some random hardware at the same ports.
Unless we test for every possible thing that may happen to lie at those
addresses (currently only the BX chipset, but who knows what the hardware
guys might come up with next).

The assumptions made in Andre Balsa's patch are:

1) basically that nothing without cpuid will ever be on a BX chipset (if
this proves to be false, then I see you have a valid point).

2) any CPU that preserves flags across division and doesn't have cpuid, is
probably a Cyrix and we may play with 0x22,0x23 ports (True w/ current
hardware).

[As always, I believe this is true, but please correct me if I'm wrong]

--
Rafael


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