RE: [Xen-users] X86_64 and 4GB RAM

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

John, 


> any ideas on where to go from here?
> Is it normal for it to only show
> Upper memory (to first chipset hole): 3144640K
> at the grub boot menu?

What revision of processor do you have, and how large is your graphics
memory? 

If you have a graphics card that eats a fair bit of memory (256 or
512MB) on a processor that doesn't support "memory hoisting"[1] (i.e.
remapping of "behind PCI memory" to a higher address), then I wouldn't
be surprised if you don't see more than 3.x GB - the reason being that
the rest of the memory is "behind" the PCI bus devices. 

Processors from Rev E has a more "flexible" memory hoisting
functionality, where there is a proper "set of memory hole registers". 

Also, if you have a newer processor you may need a new BIOS to support
this, and you'll possibly also need to enable "memory hoisting" (or
memory hole or some such) in the BIOS setup. 

[1] All processors do have a form of memory hoisting using the
"chipselect" method, however, this is only possible to use under certain
conditions, and it's limited to moving a whole chipselect-bank at a time
[which in your case may be 1-2GB, and the BIOS may deem it better to
leave a few hundred MB below 32-bit than to move a whole heap of 1 or
2GB above the 4GB boundary - particularly since a majority of users
still prefer to use 32-bit OS's that can't get past 4GB!]. 

--
Mats
> 
> Thanks
> 
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