Re: lost memory on a 4GB amd64

[Sergei Haller]

On Thu, 16 Sep 2004, Andrew Walrond (AW) wrote:

AW> On Thursday 16 Sep 2004 05:48, Sergei Haller wrote:
AW> > Hello,
AW> >
AW> > A friend of mine has a new Opteron based machine (Tyan Tiger K8W with two
AW> > Opteron 24?) and 4GB main memory.
AW> 
AW> Typo? Tyan Thunder?

no, it's a tiger: http://www.tyan.com/products/html/tigerk8w.html

AW> > the problem is that about 512 MB of that memory is lost (AGP aperture and
AW> > stuff). Although everything is perfect otherwise.
AW> > As far as I understand, all the PCI/AGP hardware uses the top end of the
AW> > 4GB address range to access their memory and there is just an
AW> > "overlapping" of the addresses. thus only the remaining 3.5 GB are
AW> > available.
AW> >
AW> >
AW> > Now there is an option in the BIOS called "Adjust Memory" which puts a
AW> > certain amount of memory (several choices between 64MB and 2GB) above the
AW> > 4GB address range. I tried the 2GB setting which results in 2GB main
AW> > memory at addresses 0-2GB and 2GB memory at addresses 4GB-6GB.
AW> >
AW> 
AW> Ok;
AW> 
AW> Assuming bios version 2.02.

yes

AW> The option you mention should be set to 'Auto'
AW> 
AW> Chipset->Northbridge->Memory Configuration->Adjust Memory = Auto
AW> 
AW> but set
AW> 
AW> Advanced->Cpu Configuration->MTRR Mapping = Continuous

I had "MTRR Mapping = Continuous" set all the time and tried "Adjust 
Memory" in all three modes (Auto/manual/disabled) and manual with 1 and 
2gb size.

today I had discovered the MTRR option and changed it to "discrete".
tried "Adjust Memory" manually at 2gb. 

the only working (but with loss of memory) combination seems to be "Adjust
Memory = disabled" and independant of "MTRR Mapping".

The only combination I didn't try is "MTRR Mapping=Discrete"+"Adjust
Memory= Auto". Will try tomorrow morning.


AW> That fixed it for me if I remember correctly :)

do you have a thunder or a tiger? And could you check in your BIOS setup 
whih options you used?



thanks,
        Sergei
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