From: Andrew Walrond <andrew@walrond.org>
To: linux-kernel@vger.kernel.org
Subject: Re: lost memory on a 4GB amd64
Date: Thu, 16 Sep 2004 14:48:38 +0100
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Cc: Sergei Haller <Sergei.Haller@math.uni-giessen.de>
References: <Pine.LNX.4.58.0409161445110.1290@magvis2.maths.usyd.edu.au>
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On Thursday 16 Sep 2004 05:48, Sergei Haller wrote:
> Hello,
>
> A friend of mine has a new Opteron based machine (Tyan Tiger K8W with two
> Opteron 24?) and 4GB main memory.

Typo? Tyan Thunder?

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

Ok;

Assuming bios version 2.02. (upgrade if you haven't already);

The option you mention should be set to 'Auto'

Chipset->Northbridge->Memory Configuration->Adjust Memory = Auto

but set

Advanced->Cpu Configuration->MTRR Mapping = Continuous

That fixed it for me if I remember correctly :)

Andrew Walrond
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