[gentoo-user] Re: BIOS says 2GB, MemTest86 says 2GB, top says 900MB

[Mark Knecht <markknecht@gmail.com>]

On Mon, Jan 18, 2010 at 6:09 PM, Mark Knecht <markknecht@gmail.com> wrote:
> One of my machines smoked last week so when tearing it apart for spare
> parts I noticed the the PC2700 CL 2.5 memory is what my wife's machine
> uses and she had only 512MB so I took the opportunity to throw in a
> couple of DIMMs. When I boot Linux (and I'm writing this from Linux
> running the new memory so the machine works) top reports only about
> 900MB while BIOS itself says 2GB. I fired up memtest86 and it reports
> 2GB. It's been running memory tests for a couple of hours now with no
> problems so it seems like it should work.
>
> Is there anything in the kernel config that would stop a 2.6.32-gentoo
> kernel from seeing all the memory?
>
> I have double checked that the memory does seem to be seated well in
> the DIMM sockets.
>
> The box is an old eMachines thing that has no support and so far I
> can't find any BIOS updates.
>
> How does memory get reported up to the kernel? Is that something in
> the kernel (i.e. - choosing the proper chipset support or something)
> or is it purely the return from some sort of BIOS call? If so can it
> be tested or circumvented to get the machine to recognize everything
> I've put in?
>
> Thanks,
> Mark

A very simple test - booting from an old Gentoo install CD - shows 2GB
- so apparently it's a kernel config issue.

Sorry for the noise.

Cheers,
Mark