Dell Latitude D620 with 4GB RAM
My Dell Latitude D620 at work had a 1024MB DDR2-667 PC2-5300 SO-DIMM. I purchased two 2048MB DDR2-677 PC2-5300 SO-DIMMs to try to expand RAM to 4096MB.
My operating system is Ubuntu hardy (development branch) running kernel 2.6.24-15-generic.
With BIOS Revision A02 and 3072MB RAM installed, I was able to use ~ 3033.5MB.
$ head -1 /proc/meminfo MemTotal: 3106300 kB
Surprisingly, with BIOS Revision A02 and 4096MB RAM installed, I was only able to use ~ 3033.7MB!
$ head -1 /proc/meminfo MemTotal: 3106464 kB
After upgrading my BIOS to the BIOS Revision A09 (D620_A09.EXE) using the process here, I was still only able to use ~3287.5MB.
$ head -1 /proc/meminfo MemTotal: 3366396 kB
Note: Running kernel 2.6.24-15-generic did not significantly change the amount of available RAM.