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2x Threadripper 7980x 64-cores or AMD Epyc 9654 96-cores?

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Old   January 29, 2024, 14:41
Default 2x Threadripper 7980x 64-cores or AMD Epyc 9654 96-cores?
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First of all, sorry for my poor English, I am Brazilian.

I am budgeting a workstation for my work, aiming to perform CFD tasks in two software applications, StarCCM+ and OpenFOAM. However, I don't have much knowledge about CFD. I am unsure about these options, 2x AMD Threadripper 7980X 64-cores (totaling 128 cores) or AMD Epyc 9654 96-cores. Is there a significant difference between them? What should I take into consideration? We have a good budget, but if I can save money, it would be better.

Thank you in advance!
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Old   January 30, 2024, 04:06
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Even if we could have two TR 7980X in one shared memory system, it would be outperformed by a single Epyc 9654 in parallel CFD applications.
But we can't, Threadripper is single-socket only.
For the 7000 series of TR, the non-pro versions only have 4 memory channels. The pro versions get 8. And Epyc 9000 series CPUs have 12 memory channels.
Memory bandwidth matters for CFD. See this thread for some explanations: General recommendations for CFD hardware [WIP]

You can also look at the checklist in section 0 of that post, and write your answers here.
tL;dr: a machine with two medium core count Epyc 9000 CPUs is probably the best choice.
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Old   January 30, 2024, 08:56
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Quote:
Originally Posted by flotus1 View Post
Even if we could have two TR 7980X in one shared memory system, it would be outperformed by a single Epyc 9654 in parallel CFD applications.
But we can't, Threadripper is single-socket only.
For the 7000 series of TR, the non-pro versions only have 4 memory channels. The pro versions get 8. And Epyc 9000 series CPUs have 12 memory channels.
Memory bandwidth matters for CFD. See this thread for some explanations: General recommendations for CFD hardware [WIP]

You can also look at the checklist in section 0 of that post, and write your answers here.
tL;dr: a machine with two medium core count Epyc 9000 CPUs is probably the best choice.

Which software do you intend to use?

OpenFoam, StarCCM+ and Python

Are you limited by license constraints? I.e. does your software license only allow you to run on N threads?

Actually idk, but we have the full license of StarCCM+ and OpenFoam is free.

What type of simulations do you want to run? And what's the maximum cell count?

I think we are going to 10-50 million cells in our projects.

What kind of setting are you in? Hobbyist? Student? Academic research? Engineer?


Engineer.

Where can you source your new computer? Buying a complete package from a large OEM? Assemble it yourself from parts? Are used parts an option?

We are buying a complete package, taking budgets from enterprises.

Which part of the world are you from? It's cool if you don't want to tell, but since prices and availability vary depending on the region, this can sometimes be relevant. Particularly if it's not North America or Europe.

Brazil.



Our options were this Threadripper and the Epyc, but if you want to share another options, I'll be good

Edit:

We have already 2 workstations with AMD Threadripper PRO 5975WX, 32/64, 128GB RAM. We want to buy another faster for CFD. AMD Epyc 9654 or AMD Epyc 9654P, 256 GB of RAM would improve it significantly or we can get a better configuration in the same price range?

Last edited by tefo17; January 30, 2024 at 09:18. Reason: Adding information
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Old   January 31, 2024, 02:53
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Quote:
we have the full license of StarCCM+
CCM+ has tons of different licenses.
For just running regular CFD simulations in parallel, there are DOE tokens. One token equals one more thread/core you can use. And there is the "power" license, which lets you run one simulation, on an unlimited amount of threads/cores.

Anyway, let's just leave that aside for now, and focus on OpenFOAM.
The best setup is still two medium core count Epyc 9000 CPUs. Something like 2x48 or 2x64 cores.
Because two CPUs double shared CPU resources, 2x48 cores is much better than 1x96 cores.
For maximizing per-core performance (which we want with limited and expensive per-core licenses like CCM+ with DOE tokens) the Genoa-X CPUs are the best choice. The increased L3 cache really helps with CFD simulations.

The caveat: you might not find a vendor which offers 2x Epyc 9000 in a workstation form factor. In that case, you will have to settle for a single CPU.

Quote:
AMD Epyc 9654 or AMD Epyc 9654P, 256 GB of RAM
Be vigilant about the memory configuration. Epyc 9000 has 12 memory channels, and we need to fill them all with at least one DIMM. So 12 DIMMs for a single-socket machine, and 24 DIMMs for dual-socket. This will likely result in a total memory capacity of 384GB or 768GB. Be very specific about this when you put in the order with your vendor
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Old   January 31, 2024, 07:14
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Quote:
Originally Posted by flotus1 View Post
CCM+ has tons of different licenses.
For just running regular CFD simulations in parallel, there are DOE tokens. One token equals one more thread/core you can use. And there is the "power" license, which lets you run one simulation, on an unlimited amount of threads/cores.

Anyway, let's just leave that aside for now, and focus on OpenFOAM.
The best setup is still two medium core count Epyc 9000 CPUs. Something like 2x48 or 2x64 cores.
Because two CPUs double shared CPU resources, 2x48 cores is much better than 1x96 cores.
For maximizing per-core performance (which we want with limited and expensive per-core licenses like CCM+ with DOE tokens) the Genoa-X CPUs are the best choice. The increased L3 cache really helps with CFD simulations.

The caveat: you might not find a vendor which offers 2x Epyc 9000 in a workstation form factor. In that case, you will have to settle for a single CPU.


Be vigilant about the memory configuration. Epyc 9000 has 12 memory channels, and we need to fill them all with at least one DIMM. So 12 DIMMs for a single-socket machine, and 24 DIMMs for dual-socket. This will likely result in a total memory capacity of 384GB or 768GB. Be very specific about this when you put in the order with your vendor

We have Power license!

And ok, thank you for all the informations. We're going to make different requisitions and hope to find a vendor that supplies us. But your advices were great to guide us in the right way. Thank you so much for that!
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