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-   -   dual or single (http://www.cfd-online.com/Forums/fluent/28806-dual-single.html)

reza August 10, 2001 09:32

dual or single
 
dear friends please let me have your comments for a cfd workstation to run fluent it is better to use dual processor mother board with pentum iii processor? thanks reza

Jonas Larsson August 10, 2001 09:44

Re: dual or single
 
You'd be better of buying a P4. A 1.8GHz P4 will run Fluent twice as fast as a 1GHz PIII - see the benchmarks I posted here some weeks ago.

Scott Whitney August 10, 2001 12:24

Re: dual or single
 
Or if you want, a dual P4 Xeon can run almost double the speed of the single P4. The key is the size of your problem. When using more that one processor, there are two steps: 1) Iterating the governing equations for each cell assigned to each processor, and 2) Sending this information between processors. If your model is a simple calculation with few cells you will spend less time of your time on step #1. Thus as the models get smaller, step #2 begins to dominate, and you get little benefit from using two processors. However if you work with large complicated models, step #1 dominates. In this extreme you can roughly double the speed of the calculation (and in some cases more than double since the operating system takes up your computer resources on only one processor).

I've got a dual 1.7 GHz Xeon and find I need to have about 2 million unknowns (7 governing equations x 300,000 cells) to approach doubling the speed of one processor - a typical medium class problem. I've also got a dual 450 MHz machine; with this I need 500,000 unknowns to approach doubling the speed of one processor. Interpolating between these results, if you buy a dual 1 GHz P3, you really need a problem with 1 million unknowns to get lots of benefit from the second processor.

Note: there is one Fluent model that people around here claim fails on more than one processor. Do a search here to make sure that isn't the model you will need.

Jayan August 12, 2001 03:58

Re: dual or single
 
Power is important, but you must mremember that memory is the most important in Fluent, if you uses Dual P4 but your memory capacity is not enough, may be you can not running the fluent in much node. and remember chipset intel 815 have max. memory 512 MB and chipset P4 capacity of memory up to 2 GB. I think Dual P4 with 2 GB memoty is much better for your system.

reza August 12, 2001 07:38

Re: dual or single
 
dear friends i have a limited bugjet and i can't help the cost of a dual piv system with 2gb of ram.

on the other hand i was thinking that in my case i can have a dual piii and i dont know that what would be the choice, i mean what mother board with say 1000 mhz piii can work best.

is that configuration bears the limit 1mb or ram.

please let me know the choices, brands, limits, or links.

i appreciate your comments and look for your answers.


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