[elyaa]

Dear all,

I'm about to build a (rather cheap) computer for personal use. I will mainly use OpenFOAM and another in-house built solver from a company based at my university. I have a budget of 1300 swiss francs (~1400 USD) for the whole thing.

I have some questions about the CPU, as I will use the computer for quite a lot of stuff including CFD, Machine Learning (in Python/MATLAB) and a bit for gaming.

I'm not tempted by GPU acceleration for the moment, so the GPU will be based on my gaming needs (I don't need a very powerful one, just one that works well, perhaps a GTX 1660 Ti or similar)

But I'm still confused about my CPU choice, and based on a first estimation, my budget for the CPU lays around 450~550 USD. Here are my first thoughts:

-AMD Ryzen 9 3900X (downside is 2 channel, not good for CFD scaling but good for the rest)
-A similar range Threadripper (opposite of the above)
-A similar range Intel Core

Thing is I read that the Ryzen 9 3900X performs quite well also for CFD even with 2 channels, and the new generation is coming in a month, so I was wondering if it's worth it.


Thank you !

[Simbelmynë]

3900X is not a good choice in terms of price/performance.


With a 1660 Ti for gaming I think almost all current generation CPUs will be sufficient. So then the question is how you can get maximum CFD performance per dollar.


Is it possible to buy used hardware?


If not, then I would probably opt for an X570 motherboard setup with a Ryzen 3600 and some low latency DDR4 at 3600 MHz minimum. Next generation Ryzen will most likely manage even higher frequencies while keeping the infinity fabric at 1:1, so then you have a clear upgrade path.


Intel has similar dual channel setups, however in the benchmark thread we have not seen the same performance. I believe this is not due to the CPU but rather because the benchmarks have not been performed with optimal RAM settings. The Ryzen benchmarks have used the Ryzen DRAM Calculator to fine tune memory settings and it seems this has a huge impact on the results.


Intel HEDT options will give you better performance, especially if you do not wish to fiddle with overclocking. 9800X is approx. 400 Euros. This is excellent value in this price range. It will fit all your gaming needs and it will be better at CFD than 3900X, at least if both systems use similar memory settings. Perhaps Zen 3 will be a better option, but at least in terms of theoretical memory bandwidth the 9800X should win. We will probably know in a month or two.


Tl:dr I would go with a 9800X or a used system.

[elyaa]

Thank you !


I have no problem to buy a used CPU, what would you advise me to buy in that case ?


For the moment I'm planning to go with a 9800X and overclock (I don't see a good reason to pay extra to go for an i9 10 core), 3600 CL16 RAM, some good cooling, and a good nvme SSD.



I'll also wait to see what new Zen 3 has to offer, even if also I doubt that a 2 channel will beat any 4 channel if both are paired with optimal RAM settings.




P.S. Does anyone know where to buy used systems in europe ?

[sharonyue]

For 1400 USD, the best option is to buy a used server. In certain cases, due to the memory channel, it is not as that slow as you expect.
We also want to try Zen3, and I think we will buy several CPUs when they are released to make a test and share our results.