Weird Real memory reported with 5.4 PAE support

David Kirchner dpk at dpk.net
Fri Sep 30 10:14:03 PDT 2005


On 9/30/05, Tamouh H. <hakmi at rogers.com> wrote:
>
> Hello,
>
> We have a Supermicro that has Winston 4GB of ECC Registered DDR333 RAM. Dual
> Xeon Processors.
>
> With PAE enabled, it seems the system reports 6GB of realmemory instead of
> 4GB, as below:

We've seen similar stuff with Supermicro servers. PCI/PCI-X/PCI-E (or
something like that) uses memory addresses in the upper end of the 4GB
barrier. The BIOS remaps any real memory above that. The more PCI
slots you have the more is reserved, and the higher the BIOS has to
remap it. (Someone can correct me if I'm wrong here, I may be
oversimplifying).

The panics you are seeing are a known bug in FreeBSD 5.4-RELEASE. The
bug is fixed in 5-STABLE:

http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/i386/i386/pmap.c.diff?r1=1.494.2.9&r2=1.494.2.10&f=h

For an unknown reason, the patch has not been commited to the
5.4-RELEASE-p* branches, or 5.4-STABLE. If you don't want to move all
the way to 5-STABLE you can just make the above changes manually (it's
just 2 lines) and rebuild, and it'll work fine.


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