[Bug 30745] Only 2.9 GB out of 4 GB appear

[Ben Collins]

Public bug report changed:
https://launchpad.net/malone/bugs/30745

Task: ubuntu linux-source-2.6.12
         Status: Needs Info => Rejected

Comment:
This is pretty much a hardware problem. At the top of dmesg, you'll notice these lines:

BIOS-e820: 0000000000000000 - 0000000000094800 (usable)
BIOS-e820: 0000000000094800 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000c2000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000bff20000 (usable)
BIOS-e820: 00000000bff20000 - 00000000bff2d000 (ACPI data)
BIOS-e820: 00000000bff2d000 - 00000000bff80000 (ACPI NVS)
BIOS-e820: 00000000bff80000 - 00000000c0000000 (reserved)
BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
BIOS-e820: 00000000fec00000 - 00000000fec00400 (reserved)
BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
BIOS-e820: 00000000fff80000 - 0000000100000000 (reserved)

Out of the two areas marked by your BIOS as "usable", the totlas come up to:

Usable1: 608256
Usable2: 3219259392
Total  : 3219867648
Total  : 3144402k

This closely matches what Linux detects:

Memory: 3084928k/3144832k available (1901k kernel code, 0k reserved, 1022k data, 192k init)

So the kernel is doing what the BIOS says it can do, and nothing more. I know that a machine I had was 512Megs of ram, but 96 of it was shadowed and reserved for various hw level things (like VGA memory). So this may be what's happening to you. I can see that the total memory showed by your BIOS is indeed for 4GB (0x100000000 is 4GB), but all of the reserved areas is why Linux can only use 2.9G of it.