4G Memory Only Recognised 3.4G

[Cameron Hutchison]

John DeCarlo wrote:

>On Dec 17, 2007 7:26 PM, Soo-Hyun Choi <s.choi at hackers.org.uk> wrote:

>> Recently, I have installed 4 x 1GB memory sticks with Ubuntu 7.10, but my
>> system only sees it as 3.4GB. Is this a typical phenomenon? Or, how can I
>> fix this problem?
>>

>The first reply had it about right.  A 32 bit system can only address 4 GB.
>When you have less than 4 GB memory, the system can map your BIOS and video
>memory and other items to unused addresses.  When you have 4 GB, you see
>that the result of this mapping means you can't use all your RAM.

>You could try using a 64 bit version of Ubuntu, then you will see all your
>RAM.

I have the same problem, but I am using a 64 bit version of Ubuntu:
# uname -m
x86_64
# free
             total       used       free     shared    buffers     cached
Mem:       3614168    3325016     289152          0       3940    1540088
-/+ buffers/cache:    1780988    1833180
Swap:      3903776          4    3903772

When I went from 2GiB to 4GiB, I had to boot with the kernel command
line parameter "mem=4G" in order to stop the machine hanging on boot
(something related to the ACPI module I think).

I have a Core 2 Duo E6600 in a Gigabyte DS3 Motherboard (ICH8).

Anyone have any ideas how to get my extra half gig back?