Dual Opteron -- FC2 won't recognize RAM

[Serge de Souza]

Craig White wrote:
> On Fri, 2004-07-23 at 20:36, Ed Hill wrote:
> 
>>Hi folks,
>>
>>Today, I installed FC2 on a dual Opteron-140 with 12Gig RAM.  The
>>install would only work if I added "mem=1024M" or similar as a kernel
>>option.
>>
>>After the install (which went nicely), the system would only boot if
>>less than 4Gig was specified using the kernel option "mem=3900M" or
>>similar.  Anything over 4Gig resulted in an immediate re-boot (reset?)
>>within a second or two of the attempted boot.
>>
> 
> ----
> I don't know about FC-3 but I definitely recall discussions in RHL about
> kernel being compiled without the options for big memory (of course,
> this applied to the 2.4 kernel and I would suppose kernel compile
> options are somewhat different with 2.6 kernel.
> 
> 
> Craig


That sounds right Craig. In the kernel you have to first activate 
HIGHMEM, then there are 2 size options in 2.6: 4GB and 64G

I don't have a FC2 box at hand and am in a bit of a hurry but have a 
look in /boot at the config file for your kernel (if using a kernel 
installed from and RPM, otherwise .config in /usr/src/linux-2.6) for 
something like this:

CONFIG_NOHIGHMEM=y
# CONFIG_HIGHMEM4G is not set
# CONFIG_HIGHMEM64G is not set

and make sure that the last one is activated (in this example it is not, 
neither is high mem). If it is not, it would explain why it only sees 
4GB and you have earned the right to recompile your kernel ;)

Serge