Re: [RFC] Cachemap for 2.6.12rc4-mm1. Was Re: [PATCH] enhance x86MTRR handling

From: H. Peter Anvin
Date: Fri May 13 2005 - 18:46:38 EST


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

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