System Ram Not Completely Recognized

Levi Pearson levipearson at gmail.com
Thu Jun 27 09:29:19 MDT 2013


On Wed, Jun 26, 2013 at 4:09 PM, Nathan England <nathan at nmecs.com> wrote:
>
> I have an AMD A6 that I use as a development server in my office. I have two similar 4 GB
> sticks of ram installed in the proper channel and the BIOS recognizes 8192MB ram in
> unganged mode.
>
> The system has an integrated Radeon HD blahblahblah video chipset and in the BIOS I have it
> set to 64MB, so the IGP should not be the issue.
>
> I have been running CentOS 6.4 which only recognized 5.3 GB of ram installed. I decided to
> play a test and see if Ubuntu 12.04 LTS or even 13.04 would recognize more ram. I downloaded
> Kubuntu 13.04 (live desktop) and booted it on this system. I swear up and down it recognized
> all 8GB of ram, so I decided to dump CentOS and I installed Ubuntu Server 12.04 LTS and only
> recognized 6GB of ram. So then I installed Ubuntu Server 13.04 and it only recognizes 6GB of
> ram. I booted the system with the Kubuntu disc again and it says 6GB of ram, so I must have
> misread it initially. Anyway, I now have 6GB instead of 5.3 which is a step in the right direction.
>
> What else could be causing this issue? Yes, this is ubuntu-13.04-amd64. Is there a command I
> can feed grub to force recognition? Google is returning everything under the sun for 32-bit pae
> and 6gb of ram, which do not apply to me!
>
> any help would be greatly appreciated!

I'm not sure what to tell you, except that DRAM controller
initialization is typically done in the BIOS on PC platforms.  There's
no such thing in a lot of embedded systems, so there either the
bootloader or kernel have to do it, and screw-ups there can cause some
memory to not get recognized or general system instability, but it's
something that has to be done *very* early in the boot process.

What does your BIOS say about how much memory the system has?  If the
BIOS and OS disagree, which seems very bizarre, you might try your
live desktop again and take note of the kernel version and
configuration.  If the BIOS doesn't recognize it, you probably need to
figure out which stick is not being recognized and replace it with one
your BIOS can handle.

        --Levi


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