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Julian121 January 28, 2019 09:17
Budget workstation
 
I am planning to buy a budget workstation which will be used primarily for CFD simulations in CFX and Fluent.

I have the following choices which cost almost the same:

2* 2680 v3

1* Epyc 7281

Which one would you think is better in terms of performance? Is there any better choice than these processors?

In addition to these processors, an amd epyc 7551 es that has 32 cores is sold $599 in ebay. Does it worth buying?

Julian121 January 29, 2019 10:39
I know that engineering sample processors do not have good performance as OEM ones.

Could you please share your advice on the two processors?

flotus1 January 29, 2019 15:40
Tough call. If you intend to get only one Epyc CPU without an upgrade path to a second CPU, get one with a P suffix. They are generally cheaper than their dual-socket capable counterparts.
But then again, the dual Xeon system will be slightly faster for pretty much anything. So the only reason to go Epyc seems to be an upgrade path with a second CPU. This would require you to buy a dual-socket board.

Have you factored in the cost for memory? Depending on how much RAM you need, Xeon E5 v2 with cheap DDR3 is still a valid budget option.

I can't recommend Epyc ES CPUs. All I read about them was from people having issues getting them to run at all.

Julian121 January 30, 2019 06:48
Quote:
Originally Posted by flotus1 (Post 723299)
Tough call. If you intend to get only one Epyc CPU without an upgrade path to a second CPU, get one with a P suffix. They are generally cheaper than their dual-socket capable counterparts.
But then again, the dual Xeon system will be slightly faster for pretty much anything. So the only reason to go Epyc seems to be an upgrade path with a second CPU. This would require you to buy a dual-socket board.

Have you factored in the cost for memory? Depending on how much RAM you need, Xeon E5 v2 with cheap DDR3 is still a valid budget option.

I can't recommend Epyc ES CPUs. All I read about them was from people having issues getting them to run at all.
I think I read somewhere on the forum that since Epyc processors are octa channel, they should outperform Xeon (v2 or v3) processors which are quad channels. But since my budget is limited, I cannot afford to buy two Epyc processors now.
Is it possible to estimate how slow a dual 2680 v3 will be compared to a dual 2680 v2 for CFD simulations in CFX? Does it differ too much?
As you said, DDR3 is cheap and I can save money to buy a SSD drive, but it depends on how slow will be a v2 than v3.

flotus1 January 30, 2019 12:11
Quote:
I think I read somewhere on the forum that since Epyc processors are octa channel, they should outperform Xeon (v2 or v3) processors which are quad channels.
As a matter of fact, you will have 2x quad-channel with the Xeon CPUs and octa-channel (4x dual-channel to be more precise) with one Epyc CPU. So the difference is not huge apart from slightly higher memory frequency with Epyc. DDR4-2666 max vs. DDR4-2133.

Quote:
I cannot afford to buy two Epyc processors now.
You could still buy one with a dual-socket board and upgrade later. If you are 100% sure that you won't do that get the Epyc 7351P instead.

Quote:
Is it possible to estimate how slow a dual 2680 v3 will be compared to a dual 2680 v2 for CFD simulations in CFX?
Given a similar choice of CPUs, the difference will be in the order of 20%. The closest competitors here are E5-2690v2 and E5-2667v2.


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