5

My ubuntu 64-bit 11.10 installed box has 6GB RAM but Ubuntu only uses 4.1GB.

I have read various things about the 4GB limit etc, but all those talk about using less than 4GB.

What could be causing this?

My Hardware:

  • Asus P5Q Pro
  • Intel Core 2 Quad Q6600 @ 2.40GHz x4
  • GeForce 9600GT (1024MB) Card not integrated
  • 3x 2GB DDR2 RAM Modules - PC-6400

Output of uname -a

Linux ASUS-P5Q-PRO 3.0.0-13-generic #22-Ubuntu SMP Wed Nov 2 13:27:26 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux
neildeadman
  • 416

2 Answers2

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Check in the BIOS to see if there is a setting for 32-bit & 64-bit HPET timer. I've found when the HPET is set to 32-bit, it tends to not address all of the memory available. I don't know how a timer can play in this, but make sure it is set to 64-bit. I could be reaching here, but it's worth a shot.

@jpyper on Twitter.

John
  • 11
1

In my question above, I stated that the BIOS saw the 6GB. I said this because when booting, as it showed the device info etc before booting, it listed 6GB of RAM.

John suggested I look for a setting for HPET and in doing so, I discovered that the BIOS Setup was reporting that the only usable amount of System Memory was something like 4.3GB.

This obviously shows it wasn't a Ubuntu problem (wish I'd found this sooner!) and replaceing one of the 2GB sticks for 2x 1GB sticks gives me the 6GB I was looking for.

My memory config before was:

DIMM0: 2GB DDR2
DIMM1: 2GB DDR2
DIMM2: 2GB DDR2
DIMM3: EMPTY

My configuration now is:

DIMM0: 2GB DDR2
DIMM1: 1GB DDR2
DIMM2: 2GB DDR2
DIMM3: 1GB DDR2

This only came about because I had to remove a faulty stick! But at least it's sorted now!

neildeadman
  • 416