Re: AMD64, 4GB, mttr questions

[Prakash Punnoor <prakash@punnoor.de>]

Am Mittwoch Januar 25 2006 01:13 schrieb Robert Hancock:
> Prakash Punnoor wrote:
> > I have a machine with 4GB RAM, an Athlon64 X2 and following mttr entries:
> >
> > reg00: base=0x00000000 (   0MB), size=4096MB: write-back, count=1
> > reg01: base=0x100000000 (4096MB), size=2048MB: write-back, count=1
> > reg02: base=0x80000000 (2048MB), size=2048MB: uncachable, count=1
> >
> > First of all, why is there an uncachable region? Is it the upper half of
> > memory? Or is this just a hole and the remaining 2GB are seated at
> > 0x100000000 ?
>
> Your e820 memory map shows the first 2GB of RAM is at 0-2GB and the
> remaining 2GB is at 4-6GB, so yes there is a hole. This doesn't explain
> why all of 0-4GB is set as write-back and then the top half of it is
> also set as uncacheable. This will presumably have been set up by the
> BIOS though, I don't think the kernel does this.

OK thanks to both of you for clearing this up. :-)

Cheers,
-- 
(°=                 =°)
//\ Prakash Punnoor /\\
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