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Date: Wed, 28 Sep 2005 07:10:30 -0700
From: David Kirchner <dpk@dpk.net>
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To: Nelis Lamprecht <nlamprecht@gmail.com>
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Cc: freebsd-questions@freebsd.org
Subject: Re: Intel 2U server 4GB RAM showing only 3GB
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On 9/28/05, Nelis Lamprecht <nlamprecht@gmail.com> wrote:
> Hi,
>
> I have a new dual Xeon Intel 2U server which I'm configuring with
> FreeBSD 5.4 and I can't get it to see more than 3GB RAM. If I try use
> the MAXMEM=3D(4096*1024) option it fails to boot up and just resets
> itself. Do I need to use the PAE option ? ..I wouldn't think so as
> this is meant for >4GB.

Yeah, you'll need to use PAE. Some BIOS apparently remap the top few
hundred megabytes (I've seen it use up to 768MB or so) for PCI (-X,
-Express?) devices.

FreeBSD 5.4-RELEASE, unpatched, has a bug that causes kernel panics
when you use PAE and memory above the 4GB barrier is accessed. The bug
is fixed in 5.4-STABLE, as of a while ago. I'm not sure if it made it
back in to any of the 5.4-RELEASE-p?? patches.