[Sergi_cfd]

Hi all!

Since December 2019, my currently build is as follows:

• AMD Threadripper 3960x
• ASUS TRX40 E-Gaming motherboard
• G-Skill Ripjaws V with 256GB RAM @3600MHz (upgraded in 2021)
• Samsung 980 Pro and 990 Pro with 2TB each (upgraded in 2023)
• Gigabyte RTX 3070 Gaming OC (upgraded in 2023)
• Corsair HX850i PSU
• Alphacool Eisbaer Pro Aurora 280 AIO (top mounting as an exhaust) (upgraded in 2024)

Back in 2019 I had a Corsair 780T case, but it was too big for my needs, and I sized it down to a Lian Li Lancool 3. Again, I found it big, and I narrowed it down to a Thermaltake Ceres 300, which is my current PC case.

But now I want to go even smaller and I'm considering going for the M-ATX route, which the only available option is to go for consumer desktop options and dual channel memory instead of the quad channel from my Threadripper.

I use Star CCM+, but not as much as I used to use it at the beginning. It's not my main use case anymore, but I don't want to completely elimitate it. So, I want to get a compromise between just web browsing, gaming and CFD with the power on demand license.

Is it an option to go for what AMD and Intel will offer with their Zen 5 and Arrow Lake future launches?

It's worth mentioning to say that money is not an issue (but considering TR 7000 series it's an issue because it's too expensive for my budget).

Thanks in advance to all of you!

[wkernkamp]

Originally Posted by Sergi_cfd

Hi all!

Since December 2019, my currently build is as follows:

• AMD Threadripper 3960x
• ASUS TRX40 E-Gaming motherboard
• G-Skill Ripjaws V with 256GB RAM @3600MHz (upgraded in 2021)
• Samsung 980 Pro and 990 Pro with 2TB each (upgraded in 2023)
• Gigabyte RTX 3070 Gaming OC (upgraded in 2023)
• Corsair HX850i PSU
• Alphacool Eisbaer Pro Aurora 280 AIO (top mounting as an exhaust) (upgraded in 2024)

Back in 2019 I had a Corsair 780T case, but it was too big for my needs, and I sized it down to a Lian Li Lancool 3. Again, I found it big, and I narrowed it down to a Thermaltake Ceres 300, which is my current PC case.

But now I want to go even smaller and I'm considering going for the M-ATX route, which the only available option is to go for consumer desktop options and dual channel memory instead of the quad channel from my Threadripper.

I use Star CCM+, but not as much as I used to use it at the beginning. It's not my main use case anymore, but I don't want to completely elimitate it. So, I want to get a compromise between just web browsing, gaming and CFD with the power on demand license.

Is it an option to go for what AMD and Intel will offer with their Zen 5 and Arrow Lake future launches?

It's worth mentioning to say that money is not an issue (but considering TR 7000 series it's an issue because it's too expensive for my budget).

Thanks in advance to all of you!

I would wait for 9950X3D. Hopefully it has 3D cache on both chiplets. The FCLK might be 2400. With a 2:1:1 ratio MCLK:UCLK:FCLK you might want to get DDR5-9600 in case the FCLK is 2400 max. If the stars align, that machine will outperform your threadripper.

[Sergi_cfd]

Originally Posted by wkernkamp

I would wait for 9950X3D. Hopefully it has 3D cache on both chiplets. The FCLK might be 2400. With a 2:1:1 ratio MCLK:UCLK:FCLK you might want to get DDR5-9600 in case the FCLK is 2400 max. If the stars align, that machine will outperform your threadripper.

Thanks for your answer!

So, the 3D version would be better when it comes to CFD than the non 3D version because of the higher L3 cache?

And then, there's another doubt. These DDR5-9600 RAM sticks as far as I'm concerned, they don't exist yet. But in any case, does it make any sense to go for the maximum allowed of 192GB (at a lesser MCLK)? Or could it be just ok going for a lesser total amount of dual channel RAM?

By the looks of it (i'm not quite familiar yet with DDR5 specs), DDR5 it has higher latency values than DDR4 for the same given amount of RAM. So perhaps, at a lesser total amount of DDR5 ram, if the latency is lower, the results may be better than going up to the maximum allowed but with a higher latency and a lower frequency speed. Am I right on this assumption?

Thanks!

[wkernkamp]

I have a 7800X3D with DDR5-6200. It does well on the Openfoam Benchmark. With a single chiplet, the performance is limited by the FCLK of 2067 MHz with 1:1:1 FCLK:UCLK:MCLK. With two chiplets, that FCLK driven bandwidth is doubled. It becomes well matched with the memory bandwidth. However, for the 7000 series, just one of the chiplets has the 3D cache, so the cpu is not symmetrical. I think that will change for the 9000 series. So my ideal chip would be the one I recommended.


The DDR5-9600 is not currently widely available, but neither are the 9000X3D.


If you want to purchase now, I would go for the 7950X3D. For CFD you need the cpu to prefer the chiplet with the 3D cache. I suspect the best performance for CFD results when using 12 cores on this 16 core chip. Eight cores on the chiplet with 3D cache and four on the other one. Cache enhances performance because there is less swapping in and out of RAM. So for the same RAM bandwidth there is better performance on CFD.


My 7800X3D can run at DDR5-6400, however it causes the CFD to fail with numerical errors. I would like to try a higher FCLK and UCLK of 2167 (which works fine), with DDR5-8666 so MCLK is 4333 MHz. That would speed me up ~ 5%.