4 GB RAM showing up as 3, BIOS memory hole and all that
ghelmer at palisadesys.com
Tue Aug 16 21:46:27 GMT 2005
Scott Long wrote:
> Intel Xeon systems typically do the remapping trick, so when you boot
> FreeBSD i386+PAE or amd64 on them, they might show 4.5GB of RAM when
> there reall is only 4GB (this is a limitation of how we compute RAM and
> is purely cosmetic, but should be fixed). Many AMD Opteron systems do
> not do the remapping and result in you loosing effective RAM. The
> difference between Intel and AMD is because AMD puts the memory
> controller into the CPU instead of in the PCI host bridge, so it's
> much harder to have the two work together to do the remapping. I
> believe that there are some Opteron systems that can do this, though.
Ahh, that helps explain something. I got excited yesterday when I
noticed a Supermicro H8DAR-8 that I thought had 8MB of RAM reported 10GB
of physical memory instead.
Guy Helmer, Ph.D.
Principal System Architect
Palisade Systems, Inc.
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