[vox-tech] Kernel not seeing all my RAM

Bill Broadley bill at cse.ucdavis.edu
Tue Feb 3 23:30:29 PST 2009


Cam Ellison wrote:
> Well, as I go back and read what it actually says in xconfig, it's for a 
> 32-bit processor with more than 4G of RAM:
> 
> 64GB (HIGHMEM64G)
> 
> Select this if you have a 32-bit processor and more than 4
> gigabytes of physical RAM.

Ah, I stand corrected.  There are two levels of PAE I believe, one where the
kernel gets a context, and all user space gets a second.  The 64GB is one
context per process I believe (with the added overhead).  Not sure how exactly
things like video card memory count though.  It's directly addressable, it
might trying 64GB if 4Gb doesn't help with the missing GB problem.

I believe I've seen cases where BIOS settings also contributed.

> I'm not going to quote what it says under "off" - it's too long - but 
> maybe he should read that and see if he can't find the answer.  My 
> interpretation is that it should be Off for a "64-bit processor".

Correct, a 64 bit CPU doesn't need any help addressing er, something like 64GB
ram.


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