[TriLUG] 32+ GB RAM PC advice

[Carlos J. Cela]

Ed,

Thank you for your detailed answer. I have been using Fedora Core for a 
while, so I guess Opteron/Fedora Core will be the combination of choice 
here...I have noticed that you can configure 32GB RAM only if you have 4 
processors installed in the machine....do you know if in a 32GB RAM/Quad 
Opteron any of the 4 processors can access the full range of memory? I 
mean, if my application is single-threaded, can I use the 32GB od RAM or 
just to 1/4th of it? is all of the memory shared? if so, why the '4 
processors installed' requirement?

Thanks,
Carlos-


Ed Hill wrote:

>Hi Carlos,
>
>For large memory systems (>4GB RAM) the Xeons are awful.  Instead, you
>should consider Opterons, Itaniums, or other hardware.  We have a number
>large-memory systems within our network
>
>  http://acesgrid.org/technical_blueprint.html
> 
>including:
>
>  + Dell dual-Itaniums w/ 16GB RAM
>  + dual-Opterons: (mostly Tyan 2885 MB w/ 16GB RAM)
>  + an Altix 350 w/ 16 CPUs and 32GB RAM
>
>and they perform *far* better than the Xeons on predominantly memory-
>bandwidth-limited scientific applications.
>
>Dual (up to 16GB RAM) and quad (up to 32GB RAM) Opteron systems can be
>purchased and/or assembled for a few thousand dollars and they scale
>*remarkably* well.  I'm very fond of our Opterons.  We see almost linear
>(that is, per-CPU) speed-ups with many applications including our main
>ocean/atmospheric modeling software.  And Linux (we use both Fedora Core
>2 for x86_64 and RHEL v3 for x86_64) runs quite nicely on the Opterons.
>
>For more than 32GB RAM, you'll have to look into SGI Altix or other
>high-end hardware.  For truly huge simulations it is often best to get
>time at a center such as:
>
>  http://www.ncsc.org/
>  http://www.psc.edu/
>
>rather than trying to buy your own.  As an academic, you can usually get
>grants of computing time on their (often huge) systems quite easily.
>
>Good luck with your simulations!
>
>Ed
>
>  
>