[Andrew Norfolk]

I've been tasked with putting together a new CAD/CFD workstation that will be running mostly CHT models on CFX. Most of the models i've run so far are 10 million cells or greater in terms of cell count. From what i've read, memory bandwidth is the limiting factor for performance in large CFD models. Based on this i've opted for a quad channel channel processor and with my price constraints i've narrowed it down to just a few CPU's:

Xeon E5-1650 v3 3.5GHz 6-Core £475

Xeon E5-2630 v3 2.4GHz 8-Core £540

i7-5930K 3.50GHz 6-Core £460

Now it's important to note that at this point in time my company only has a single core license for ANSYS CFX, however in the future we may be be acquiring a 4 core license so this build needs to be able to accommodate that.

Currently I am leaning towards the xeon E5-1650 v3 or 5930K as I believe the higher clock frequencies will provide better performance for our current (single core) and up to four core set up. The E5-2630 however does have 25% more on-board cache which could be more important given the importance of memory bandwidth. Unfortunately I couldn't find any specific CFX benchmarks comparing these three so I was hoping some of you lovely people could share your wisdom with this newbie

Any thoughts?

[flotus1]

With licenses for only one or later 4 cores, you should try to get the setup with the highest performance per core. This means you are looking for a processor with high clock speed, support for fast memory and large cache.

As far as the Xeon processors are concerned, remove everything from the list that does not support DDR4-2133MHz. So the Xeon E5-2630 v3 is out because of slow memory and low clock speed.
So if you are really on a low budget, the Xeon E5-1650 v3 is the best option.

The I7-5930k has no advantage compared to the cheaper I7-5820k, at least in a normal CFD workstation. Choosing this CPU over a Xeon CPU with ECC memory only makes sense with overclocking. If you know what you are doing you can sqeeze out a performance increase of 40% or more compared to the setup with the Xeon processor. Otherwise you are better off with the Xeon.

A note on your tight budget: If you have to pay full price for your Ansys licenses, hardware costs should be the last thing to worry about. You usually spend whatever it takes to get the fastest computer possible and make the most out of the expensive licenses.

[Andrew Norfolk]

Thanks for your thoughts.

Originally Posted by flotus1

A note on your tight budget: If you have to pay full price for your Ansys licenses, hardware costs should be the last thing to worry about. You usually spend whatever it takes to get the fastest computer possible and make the most out of the expensive licenses.

I've tried saying this. I could probably get an increase on the budget but we would still be in 4 core territory tops (multi-core licenses for 8 cores or more are super expensive). So assuming a larger budget, are there even any processors out there that could offer significantly better performance given this limitation?

In terms of overclocking, I've got a bit of experience here myself so this is an option.

[flotus1]

With more money to spend on the CPU, you could get one with a larger cache.
Xeon E5-2643 v3, 6x 3.40GHz, 20MB
Intel Xeon E5-2687W v3, 10x 3.10GHz, 25MB
I7-5960X, 8x 3.00GHz, 20MB