SOLVED: Only 3.6gb of 64gb RAM recognized by 64bit squeeze
Summary:
Debian Squeeze 64-bit was not able to use more than 3.6GB RAM. Linux
showed the problem as MTRR not covering all available RAM.
MTRR problems can be fixed by kernel if MTRR repair is enabled, e.g. in
the 3.2 kernel. However, the using the backported 3.2 kernel resulted in
kernel panic.
As RAM had been tested extensively with memtest, the problem was
hypothesized to be because of faulty motherboard or BIOS.
One RMA of MB later, and everything is working with the 3.2 kernel and
"noapic irqpoll acpi=force" boot flags.
I did have a small problem: Sometimes I would get "RAM R/W test fail" at
BIOS POST. I tested if the individual DIMMs could POST, only one gave
the "RAM R/W test fail". After removing the 'faulty' DIMM + a healthy
DIMM, the system works smoothly. I have not had time to test the
'faulty' DIMM in another computer yet to see if it really is faulty.
Thank you all for your help!
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