On 9/16/07, Howard Chu <hyc@symas.com> wrote:
quoted text
> Yinghai Lu wrote:
> > On 9/14/07, Howard Chu <hyc@symas.com> wrote:
> >> Hi, was wondering if anyone else has been tripped up by this... I've got 4GB of
> >> RAM in my Asus A8V Deluxe and memory hole mapping enabled in the BIOS. By
> >> default, my system boots up with these MTRR settings:
> >>
> >> reg00: base=0x00000000 (   0MB), size=4096MB: write-back, count=1
> >> reg01: base=0x100000000 (4096MB), size=1024MB: write-back, count=1
> >> reg02: base=0xc0000000 (3072MB), size=1024MB: uncachable, count=1
> >> reg03: base=0xc0000000 (3072MB), size= 256MB: write-combining, count=1

if rev F before cpu aka Rev E is installed, and 8G RAM installed, it will be
quoted text
> >> reg00: base=0x00000000 (   0MB), size=8192MB: write-back, count=1
> >> reg01: base=0x100000000 (8192MB), size=1024MB: write-back, count=1
> >> reg02: base=0xc0000000 (3072MB), size=1024MB: uncachable, count=1
> >> reg03: base=0xc0000000 (3072MB), size= 256MB: write-combining, count=1
and you will have problem...

So good way is get the ram top, and hole size...and reset the whole
set ot var mtrr.

you could refer the code in LinuxBIOS about setting that...
http://www.openbios.org/viewvc/trunk/LinuxBIOSv2/src/cpu/x86/mtrr/mtrr.c?revision=2616...
esp the part about CONFIG_VAR_MTRR_HOLE...

but Andi and Eric said resetting mtrr is not good... when someone from
intel try to trim the MTRR for intel CPU.

YH
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