Re: [RFC] Cachemap for 2.6.12rc4-mm1. Was Re: [PATCH] enhance x86 MTRR handling

H. Peter Anvin
2005-05-13T23:39:18Z

Dave Jones wrote:
> >
> > Drop the vendor check; PAT is a generic x86 feature. If AMD is not
> > compatible (see below), then use X86_VENDOR_AMD: and default:.
>
> Done. Does transmeta have PAT btw ? I know newer VIA has it,
> but I haven't looked through the docs to double check its
> implementation yet.
>

The Efficeon (TM8xxx) series does have PAT.
>
> > >+ * Note: On Athlon cpus PAT2/PAT3 & PAT6/PAT7 are both Uncacheable since
> > >+ * there is no uncached type.
> > If one sets the PAT to "uncached", does one get the same function as
> > "uncachable"?
>
> AIUI, only as long as we don't have an MTRR covering the same range marked WC.
> It seems to be the only thing I could find documenting the differences
> between 'uncached' and 'uncacheable' in this context.
> Though I've only looked through the Intel & AMD K8 docs, I don't have
> the K7 ones to hand.
>

I mean, on the Athlon series, is it really necessary to use a different
value?

-hpa