Re: 36 bit MTRRs, Re: test10-pre1 problems on 4-way SuperServer8050

From: Boszormenyi Zoltan (
Date: Thu Oct 12 2000 - 05:21:46 EST

On Thu, 12 Oct 2000, Tigran Aivazian wrote:

> > On Thu, 12 Oct 2000, Boszormenyi Zoltan wrote:
> >
> > > echo "base=0 size=0x100000000 type=write-back" >/proc/mtrr
> this line immediately locks up the machine. But I want to understand where

We just shared an experience. :-( This is what I wrote some lines
later. Will you please set the uncached areas first? And do not forget
the last echo line I wrote.

> did you get base=0 and size=0x100000000 from? Shouldn't it be
> base=0x100000 and size=0xfccf0000 according to this entry from e820:
> BIOS-e820: 00000000fccf0000 @ 0000000000100000 (usable)

Yes, this is (4GB - whatever MB) starting at 1MB: upper 15MB of zone(0)
+ zone(1) + lower ~3GB of zone(2). The mtrr driver correctly
complains when you try to set it exactly this way because
the MTRRs base must be on size boundary. That's why I collected
the real memory areas and the should-be-uncached PCI areas.

Zoltan Boszormenyi

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