Re: 2.6.26-rc6-git2: Reported regressions from 2.6.25

Dave Jones
2008-06-17T15:31:50Z

On Mon, Jun 16, 2008 at 12:31:52AM +0100, Maciej W. Rozycki wrote:
> On Sat, 14 Jun 2008, Linus Torvalds wrote:
>
> > > From what you have written it looks the dependency should actually be:
> > >
> > > depends on !M386 && !M486 && !M586 && !M586TSC && !M586MMX
> > >
> > > as none of the pre-Pentium-Pro processors had the PAE feature (I am not
> > > sure about non-Intel implementations, so the case of M586 would have to be
> > > investigated).
> >
> > Yes, it's the non-intel ones that would keep me from saying !M586.
> >
> > For intel, PAE was a PPro feature (at least officially, as you point out),
> > but I do not know about various other manufacturers. From personal
> > experience, the line between Pentium and PPro features doesn't tend to be
> > totally black-and-white (although I suspect that when it comes to PAE it
> > _may_ be).
>
> Well, PAE is quite a significant block to implement and Intel kept it
> hidden until they published the long awaited PentiumPro manual sometime in
> 1996. I am fairly sure the K5 did not implement it (it may have had PSE
> and VME, especially in the later revisions) and Google does not show up
> any Cyrix processors with PAE. I may have a K5 manual somewhere, so I can
> see if I can verify it.

Even the K6 didn't have PAE. The Athlon was AMD's first CPU that had it.

> Please also note these processors tried to compete with Intel on the
> desktop market where 4GB of RAM was completely unreasonable in late 90s.
> I think unless someone can recall a counter-example, it can be safely
> assumed these chips did not have the PAE. We could try to extend the
> dependency and see if anybody screams.

I agree. To the best of my knowledge (and looking through output of
x86info from lots of old CPUs), Intel had the only CPUs with PAE in
that era.

Dave

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