[vox-tech] Kernel not seeing all my RAM

[Bill Broadley]

Chanoch (Ken) Bloom wrote:
> I'm upgrading an x86

Not x86-64?

> machine to 4 GB of RAM, and have compiled the
> kernel with CONFIG_HIGHMEM64G=y, but the kernel is only seeing 3283 MB
> of the RAM. Any idea what I'm doing wrong?

Nothing.  It's up to the motherboard to remap memory reserved for I/O to
memory over 4GB.  Thinks like a 256MB video card often require 768MB of
address space.

Check out BIOS for any hint of being able to remap memory, high memory, bounce
buffers for I/O, etc.

The consolidation price is that your configuration is often the highest
performance.  The only thing I can offer that might fix it (beside BIOS
tweaks) is upgrading to x86-64 (assuming the hardware is capable).

I had a machine with 3.0 GB available running centos-5 and upgraded to x86-64
(ubuntu 8.10):
# free
             total       used       free     shared    buffers     cached
Mem:       4054428    1023508    3030920          0     192656     357008
-/+ buffers/cache:     473844    3580584
Swap:      4192956       5412    4187544

Side benefits include better performance (slight) and better security.