RE: [Xen-users] amd64 system only seeing 3.5gb instead of 4gb of memory

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

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> James Harper
> Sent: 15 June 2007 06:38
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] amd64 system only seeing 3.5gb instead 
> of 4gb of memory
> 
> I've just had a server upgraded to 4gb of memory... BIOS 
> reports 4gb of
> memory but xen only sees 3.5gb (3583mb)
> 
> I was under the impression that an amd64 server should be able to see
> well over 4gb of memory. I believe that PCI space and other stuff gets
> mapped to the very top of memory... is there some setting 
> somewhere that
> I might need to set to get that .5gb mapped to somewhere visible?

Further to what has already been said (all of which is sensible and good
suggestions): 
1. Assuming you have an AMD processor, you need a procesor that is Rev E
or later. 
2. You need to have PAE or 64-bit mode to see any memory ABOVE 4GB (so
even if it's remapped, non-PAE will not be able to "get there" because
it's strictly limited to 32-bit memory addresses, which is 4GB in total
- this is why the PCI memory is located around the end of 4GB). 
3. Your BIOS must enable "memory hoisting", which is the techie name for
"move memory from under PCI space to someplace else".

--
Mats
> 
> Thanks
> 
> James
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
> 
> 
> 



_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users