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SubjectRe: [Fwd: CPU detection revamp (Request for comments)]
davej@suse.de wrote:
>
> Hi hpa,
>
> First test, the AMD K6-2.
>
> Before your patch..
> cpu family : 5
> model : 8
> stepping : 12
>
> After..
>
> cpu family : 5
> model : 8
> stepping : 4
>
> Line 1826 of setup.c
>
> c->x86_mask = tfms & 7;
>
> Should be..
>
> c->x86_mask = tfms & 15;
>
> I think?
>
> Also, look at the feature flags:
> before:
> flags : fpu vme de pse tsc msr mce cx8 sep mtrr pge mmx 3dnow
>
> after:
> features : fpu vme de pse tsc msr mce cx8 pge mmx syscall 3dnow
>
> Note, I lost MTRR & sep. This may be related to the stepping bug
> though. I'll recompile a kernel with the &15 fix, and see if that cures
> all.
>

That is actually correct -- the K6-2 doesn't actually have mtrr and sep,
but has syscall and k6_mtrr instead (the stepping bug causes k6_mtrr not
to show up.) Part of the bugginess of the old system was using one flag
for multiple purposes. This was Linux' doing, not AMD's, by the way.

> btw, whilst all this is getting a shakedown, how about renaming
> that 'x86_mask' field to the more obvious 'x86_stepping' ?
> c->x86 would make more sense as c->x86_family too thinking about it.
>

--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt
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