[MLUG] 32-bit memory hole and x86_64

[Jack Smith <EMAIL:PROTECTED>]

I am starting work on a project that requires something near 4 GB RAM,
so I added two more 1 GB DDR-400 modules to my socket 939 Athlon 64 X2
in an ABIT KN8-SLi motherboard to make 4 GB in total. (BTW, 1 GB DDR-400
memory modules are VERY hard to find locally here in Columbia, but
Staples has them at an okay price for a B&M store.) I'm running Gentoo
2007.0 AMD64, so I though that this should be a quick drop-in upgrade. I
had reset the DRAM command rate to 2T so that the memory controller
would run the RAM at the full DDR-400 with all four slots full and it
booted up just fine. 

On the first boot, the BIOS said that it only detected something like
3300000 KB RAM, so I went back in the BIOS and changed the memory hole
setting from "Disabled" to "Auto." Next bootup had the BIOS detect all
4194304 KB of RAM that was installed. I ran Memtest86+ and all of the
RAM checked out. I started up Gentoo and it only sees 4045000 KB RAM.
There are two other options for the memory hole- "Hardware" and
"Software." I booted with each of them chosen and there is still only
3950 MB RAM seen by the OS. 

I know that the kernel's allocated memory and such will make the visible
RAM be *slightly* less than the full installed amount. Previously, the
computer saw about 2015 MB out of its 2048 MB installed RAM. But losing
146 MB RAM seems a bit much and makes me think that the memory hole is
not being completely mapped above the 4 GB RAM addressing line like it
is supposed to. Any ideas?

Jack


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