mtrr funnies

[Roger Heflin]

Wolfgang S. Rupprecht wrote:
> Roger Heflin <rogerheflin at gmail.com> writes:
> 
>> Wolfgang S. Rupprecht wrote:
>> On the AMD's I remember one of the AMD experts mentioning that the
>>> 4GB memory stuff is automagic so is not listed as a MTRR at all.   It
>> is just there.
>>
>> Does "cat /proc/meminfo" and top both show around 8GB like expected?
> 
> Yes, it shows most of the 8gig.  About half a gig are missing, but
> then the bios boot screen also mentions that only 7.6 gigs are being
> made available.  I wonder why the rest isn't remapped. to the top of
> ram.
> 
> -wolfgang


I know a bios engineer once told me that some chipsets/bios can only remap 
entire dimms (not parts of a dimm) and doing an entire dimm would result in only 
2GB below 4GB and that bothers some vendors since it would cause issues with 
memory availability with 32bit only OSes.

Check to see if any bios settings change things, on the higher end boards there 
use to be a memory hole setting that could be set to hardware or software, 
though if I remember correctly setting it such that you found all of the memory 
also resulting in the machine being a couple of percent slower.

                         Roger