[Beowulf] CCL:Opteron or Nocona ? (fwd from cavallo at chemistry.unina.it)
sdm900 at gmail.com
Sat May 7 20:04:17 PDT 2005
It highly depends on your code and whether you are going to run more
than a single cpu in a box. If you are only going to purchase single
cpu boxes, I think they are more or less the same.
If, however, you are going to run more than a single cpu box, I think
it is fair to say, that the Opterons should give better performance.
Just look at the spec rate fp base and you will see that a dual
processor opteron system out perform the Nocona systems by a long way.
Each opteron chip has its own memory controller. So, if you have 2
cpu's, you have 2 memory controllers and your memory bandwidth scales
linearly. Nocona chips sit on a bus with a single memory
controller. If you have 2 cpu's you still only have 1 memory
controller, so each chip, on average, sees only 1/2 the memory
The other issue is memory latency. Because the Opterons have the
memory controller on the actual cpu chip, their latency to memory is
very very low, which gives an effective increase in memory
bandwidth. The Nocona chips have the memory controller off chip, so
their latency is high, reducing effective memory bandwidth.
There are other minor difference, but the memory sub-system is the
one that gives the biggest performance difference.
On 08/05/2005, at 3:23, Eugen Leitl wrote:
> ----- Forwarded message from Luigi Cavallo
> <cavallo at chemistry.unina.it> -----
> From: Luigi Cavallo <cavallo at chemistry.unina.it>
> Date: Sat, 07 May 2005 09:19:33 +0200 (MET DST)
> To: chemistry at ccl.net
> Subject: CCL:Opteron or Nocona ?
> we are going to invest some money for a few computers, and we have to
> make a decision between the AMD-Opterons and the Intel-Nocona. What's
> better ? We are experienced with the Opterons, but we have no idea
> the Noconas...
> Major codes to run on them will be classical QM packages as ADF,
> G03, TM,
> some AIMD as CPMD, and possibly some classical MD as gromacs.
Dr Stuart Midgley
sdm900 at gmail.com
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