physical memory support under RHEL for Opteron

[Chiu, PCM (Peter)]

Many thanks,

I have also gathered from a couple of vendors that they 
have experienced a problem in getting IDE and SATA working
to an opterons with more than 4GB of memory.  One theory is that 
quite a number of IDE and SATA controllers are still running 32-bit codes.

Peter

-----Original Message-----
From: Joshua Baker-LePain [mailto:jlb17 at duke.edu] 
Sent: 31 March 2004 18:12
To: redhat-list at redhat.com
Cc: Chiu, PCM (Peter) 
Subject: physical memory support under RHEL for Opteron


On Wed, 31 Mar 2004 at 12:00pm, redhat-list-request at redhat.com wrote

> I am just about to order an dual Opteron 248 server to run under RHEL 
> AS.
> 
> I would like to double check the physical memory supported - we are 
> getting 8 x 2GB PC3200 or PC2700 memory on this server.
> 
> I have found something a bit obscure on the RH web page: 
> 	 http://www.redhat.com/software/rhel/as/
> <http://www.redhat.com/software/rhel/as/>
> 
> in that it said:
> 
> ** 64GB is the maximum memory size for X86 systems. Maximum memory 
> sizes vary with other architectures.
> 
> Can anyone confirm
> a. the maximum memory size for Opterons supported, and
> b. the maximum usable physical memory per process on user applications

>From /usr/src/linux-2.4.21-9.EL/Documentation/x86_64/mm.txt on my RHEL3.0 
AMD64 system:

The paging design used on the x86-64 linux kernel port in 2.4.x provides:

o       per process virtual address space limit of 512 Gigabytes
o       top of userspace stack located at address 0x0000007fffffffff
o       start of the kernel mapping =  0x0000010000000000
o       global RAM per system 508*512GB=254 Terabytes
o       no need of any common code change
o       512GB of vmalloc/ioremap space

So I think you're OK with 16GB.  ;)  FWIW, that systems has 8GB and runs 
wonderfully.  Be sure to follow the recommendations in bugs 118152 and 
115438, which fix a couple of memory issues.

-- 
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University