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Gen February 19, 2008 08:02

4 (one core) or 2 (double core) processors?
Hi all! What do you recommend for parallel solving by ANSYS CFX? 4 (one core) or 2 (double core) processors; 8 (one core) or 4 (double core) processors? Thanks for your response!

Bart February 19, 2008 08:17

Re: 4 (one core) or 2 (double core) processors?
As most new (faster) processors are at least dual core, single or dual core is not really a choice (single core is just too old). You have to look at what processor is fastest PER core. So it's either 4 dual core used as single core or 2 dual core using 4 cores. Then the memory bus is the bottleneck (both cores need access to the same memory). Comparing quad cores to dual cores the fastest processors PER core are to my knowlegde still dual cores. We recently opted for Intel Xeon 5160 (dual cores) where only one core per processors is used. You can save money on hardware using all cores on the processors, but most of the money goes to the parallel licenses (paid per used core). The money/performance ratio is than shifted to using 1 parellel license per processor (using only 1 core per processor). I hope this makes sense.

Dre February 19, 2008 09:00

Re: 4 (one core) or 2 (double core) processors?
This is somewhat related. I found it very interesting.

Go Barcelona!

Bart February 19, 2008 09:53

Re: 4 (one core) or 2 (double core) processors?
Excellent link. Thanks for that. But: Go Barcelona????? Conclusion says intel Xeon 5160, taking everything into account (scaling, license cost etc). Problem with Harpertown is availability. Barcelona is good if licence costs are not an issue (free parallel codes).

Dre February 19, 2008 13:37

Re: 4 (one core) or 2 (double core) processors?
Well I think it's obvious that parallel computing is the new direction. Maybe not new, but getting cheaper, more sophisticated and more acceptance. You'll have to embrace sooner or later.

I'm also an AMD supporter :)

Glenn Horrocks February 19, 2008 17:31

Re: 4 (one core) or 2 (double core) processors?

Bart is definitely right for commercial ANSYS CFX customers - the license cost for parallel licenses far exceeds the hardware cost so Woodcrest 5160 is a clear winner on this basis. However, for academic customers who pay a far lower price for the software the equation may be different and it may be better to use a larger number of slower CPUs (such as the AMD CPUs) that run better in parallel.

Glenn Horrocks

Gen February 20, 2008 03:15

Re: 4 (one core) or 2 (double core) processors?
Thank you all! Your advices are very useful for me.

Bart February 20, 2008 04:25

Re: 4 (one core) or 2 (double core) processors?
Sniff sniff, :,-( I used to be AMD supported (had one at home also). But it looks like AMD is in its final days.

CFD: one major player: Ansys CPU: one major player: Intel

so much for competition

By the way. I had a look at the CADFEM presentation from Dre. New Harpertown Xeon CPU's are available (X5460, 3+ GHz). It might tip the scale from he Xeon 5160 to the new quad cores (buy less CPU's use them as multicore and save some on hardware with the same or more speed). I'm reconsidering my upcomming purchase of a new cluster. Thanks Dre again!!!


alterego February 21, 2008 06:35

Re: 4 (one core) or 2 (double core) processors?
Any suggestions if it would be worth the wait for the new Xeon 5482 3.2GHz with 1600 FSB to be available?

Were heading for a new server with 2 Quadcore CPUs.

Bart February 21, 2008 06:48

Re: 4 (one core) or 2 (double core) processors?
The latest information I have is that the increase in bus frequency (from 1333 to 1600 MHz) doesn't help as the Xeon memory bottleneck is still there. However, the new Harpertowns Xeon's do scale better than the older 5160 (dual cores) and are just faster per core. So I would disregard the Bus frequency and go for the fastest quad core harpertown Xeon.


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