RHEL 5.1 (32 bit) shows 3GB RAM though there's 16GB physical

[Stainforth, Matthew (SD/DS)]

> why is "top" or "dmesg" showing only 3GB RAM
> instead of 4GB if 4GB is the max the 32 bit RHEL
> can support?
> 
> Supposedly there's 16GB physical RAM inserted
> in the hardware

I don't know exactly how Linux counts memory but on other platforms you will often see this because RAM of other adapters (video being the main culprit) counts as part of the 4GB so only 3 to 3.5GB of system RAM ends up being addressable.  So that would be my guess in this circumstance.