Is the 3900x overkill?

[dcheuk]

I finally put together my 3950x, this is what I'm seeing, not exactly impressive maybe I'm missing something.

Specs: Asrock matx x570, 3950x, 4x16gb ddr4-3466 17-19-19



It's really weird this processor seldom jumps 10 degrees then goes back down, and jumps again. Temperature fluctuates a lot. This shouldn't happen, at least I didn't expect it to.

Hope this helps anyone who's planning to buy one. Let me know if you want me to run any specific tests.

[kladner]

What is the CPU cooling? I'm wondering about thermal interface issues.

Is this 4 channel memory? If so, I am in awe of such a system.
EDIT: Well I am in awe, regardless.

[dcheuk]

Originally Posted by kladner

What is the CPU cooling? I'm wondering about thermal interface issues.

Is this 4 channel memory? If so, I am in awe of such a system.
EDIT: Well I am in awe, regardless.

Nope this is only dual channel, I think only the threadrippers are quad channel.

According to data given by others i.e. The Judger on the 3900x, it seems like 3950x is not a good choice economically speaking, at least for use in Prime95. Compared to his data on FFT around DC range I think 2880K, I'm only getting a max of 790iter/ms (12 cores) compared to his 850iter/ms on the 3900x.

Cooler is the corsair h115i pro. Not sure why the temperature randomly spikes every 30 seconds or so, maybe its a ryzen thing, but guess will try to reapply thermal paste and see what happens.

Take care, everyone.

[LaurV]

Re: the new title of thread, ("is the 3900x overkill?") - there is not overkill in distributed computing world. If you can afford the money for hardware and electricity, then the more hardware the merrier...

[M344587487]

Originally Posted by dcheuk

I finally put together my 3950x, this is what I'm seeing, not exactly impressive maybe I'm missing something.

Specs: Asrock matx x570, 3950x, 4x16gb ddr4-3466 17-19-19

Attachment 22060

It's really weird this processor seldom jumps 10 degrees then goes back down, and jumps again. Temperature fluctuates a lot. This shouldn't happen, at least I didn't expect it to.

Hope this helps anyone who's planning to buy one. Let me know if you want me to run any specific tests.

You might have better luck using 4 or 2 workers, you might need to manually pin each worker to certain cores or run multiple instances of P95. A Zen2 CCX is its own unit of (up to) 4 cores and 16MiB of L3 cache, the L3 cache is only directly accessible to cores in its CCX so minimising cross-CCX communication could help.



Zen2 (and probably all CPUs going forwards) act more like a GPU by automatically boosting when thermal limits allow. Under steady load I wouldn't expect a lot of temperature jumps, maybe the load isn't steady as a result of the disjoint L3 causing some unpredictable access times or maybe 10 degrees just isn't that big a jump.



If you're in a testing mood you could try optimising for a 50M exponent with single channel memory, this would simulate quarter of a 3990X and answer part of this question ( https://www.mersenneforum.org/showthread.php?t=25463 ). The question also includes 90M and 332M exponents but unless you're particularly bored I wouldn't bother as GPUs are much better suited to large exponents.

[Viliam Furik]

Originally Posted by dcheuk

I finally put together my 3950x, this is what I'm seeing, not exactly impressive maybe I'm missing something.

Specs: Asrock matx x570, 3950x, 4x16gb ddr4-3466 17-19-19

Attachment 22060

It's really weird this processor seldom jumps 10 degrees then goes back down, and jumps again. Temperature fluctuates a lot. This shouldn't happen, at least I didn't expect it to.

Hope this helps anyone who's planning to buy one. Let me know if you want me to run any specific tests.

I have 3900X, and when I had it at stock speed and stock fan curve, it was doing exactly the same thing, jump to 50 and then slowly to 36-38 and after a few seconds again 50... Cpu temperature graph looked like saw teeth.

EDIT:
I forgot to mention now I have it on 4,1 GHz overclock on all cores, and when I turn on Prime95, I set fans to 100%, and no fluctuations whatsoever under load. I should also mention that spiking occurred only when not under load on stock settings.

[dcheuk]

Originally Posted by Viliam Furik

I have 3900X, and when I had it at stock speed and stock fan curve, it was doing exactly the same thing, jump to 50 and then slowly to 36-38 and after a few seconds again 50... Cpu temperature graph looked like saw teeth.

EDIT:
I forgot to mention now I have it on 4,1 GHz overclock on all cores, and when I turn on Prime95, I set fans to 100%, and no fluctuations whatsoever under load. I should also mention that spiking occurred only when not under load on stock settings.

Yes - this is exactly what happens to my chip. It is stable under load.

Here's some data on different FFTs, I switched to 3333mhz cas15 memory this time.

Prime95 64-bit version 29.8, RdtscTiming=1
Timings for 2560K FFT length (12 cores, 1 worker):  1.19 ms.  Throughput: 840.80 iter/sec.
Timings for 2560K FFT length (12 cores hyperthreaded, 1 worker):  1.14 ms.  Throughput: 879.66 iter/sec.
Timings for 2688K FFT length (12 cores, 1 worker):  1.19 ms.  Throughput: 838.49 iter/sec.
Timings for 2688K FFT length (12 cores hyperthreaded, 1 worker):  1.26 ms.  Throughput: 795.96 iter/sec.
Timings for 2800K FFT length (12 cores, 1 worker):  1.41 ms.  Throughput: 708.21 iter/sec.
Timings for 2800K FFT length (12 cores hyperthreaded, 1 worker):  1.52 ms.  Throughput: 658.88 iter/sec.
Timings for 2880K FFT length (12 cores, 1 worker):  1.36 ms.  Throughput: 734.25 iter/sec.
Timings for 2880K FFT length (12 cores hyperthreaded, 1 worker):  1.47 ms.  Throughput: 678.32 iter/sec.
Timings for 3072K FFT length (12 cores, 1 worker):  1.42 ms.  Throughput: 703.88 iter/sec.
Timings for 3072K FFT length (12 cores hyperthreaded, 1 worker):  1.42 ms.  Throughput: 705.53 iter/sec.
Timings for 3200K FFT length (12 cores, 1 worker):  1.47 ms.  Throughput: 678.45 iter/sec.
Timings for 3200K FFT length (12 cores hyperthreaded, 1 worker):  1.45 ms.  Throughput: 690.52 iter/sec.
Timings for 3360K FFT length (12 cores, 1 worker):  1.51 ms.  Throughput: 664.09 iter/sec.
Timings for 3360K FFT length (12 cores hyperthreaded, 1 worker):  1.46 ms.  Throughput: 684.63 iter/sec.
Timings for 3584K FFT length (12 cores, 1 worker):  1.63 ms.  Throughput: 614.33 iter/sec.
Timings for 3584K FFT length (12 cores hyperthreaded, 1 worker):  1.56 ms.  Throughput: 641.42 iter/sec.
Timings for 3840K FFT length (12 cores, 1 worker):  1.74 ms.  Throughput: 575.05 iter/sec.
Timings for 3840K FFT length (12 cores hyperthreaded, 1 worker):  1.70 ms.  Throughput: 588.05 iter/sec.
Timings for 4096K FFT length (12 cores, 1 worker):  1.84 ms.  Throughput: 543.58 iter/sec.
Timings for 4096K FFT length (12 cores hyperthreaded, 1 worker):  1.76 ms.  Throughput: 567.93 iter/sec.
Timings for 4480K FFT length (12 cores, 1 worker):  2.08 ms.  Throughput: 481.58 iter/sec.
Timings for 4480K FFT length (12 cores hyperthreaded, 1 worker):  2.05 ms.  Throughput: 487.49 iter/sec.
Timings for 4608K FFT length (12 cores, 1 worker):  2.09 ms.  Throughput: 478.69 iter/sec.
Timings for 4608K FFT length (12 cores hyperthreaded, 1 worker):  2.13 ms.  Throughput: 468.51 iter/sec.
Timings for 4800K FFT length (12 cores, 1 worker):  2.16 ms.  Throughput: 462.00 iter/sec.
Timings for 4800K FFT length (12 cores hyperthreaded, 1 worker):  2.08 ms.  Throughput: 479.87 iter/sec.
Timings for 5120K FFT length (12 cores, 1 worker):  2.34 ms.  Throughput: 428.14 iter/sec.
[Sat Apr 18 19:22:58 2020]
Timings for 5120K FFT length (12 cores hyperthreaded, 1 worker):  2.32 ms.  Throughput: 431.55 iter/sec.
Timings for 5376K FFT length (12 cores, 1 worker):  2.68 ms.  Throughput: 373.61 iter/sec.
Timings for 5376K FFT length (12 cores hyperthreaded, 1 worker):  2.84 ms.  Throughput: 352.25 iter/sec.
Timings for 5600K FFT length (12 cores, 1 worker):  2.85 ms.  Throughput: 351.09 iter/sec.
Timings for 5600K FFT length (12 cores hyperthreaded, 1 worker):  2.98 ms.  Throughput: 335.68 iter/sec.
Timings for 5760K FFT length (12 cores, 1 worker):  3.16 ms.  Throughput: 316.13 iter/sec.
Timings for 5760K FFT length (12 cores hyperthreaded, 1 worker):  3.71 ms.  Throughput: 269.34 iter/sec.
Timings for 6144K FFT length (12 cores, 1 worker):  3.45 ms.  Throughput: 290.23 iter/sec.
Timings for 6144K FFT length (12 cores hyperthreaded, 1 worker):  3.57 ms.  Throughput: 280.42 iter/sec.

EDIT: 2 Workers much faster. Tried 3/4 workers they are slower.

Prime95 64-bit version 29.8, RdtscTiming=1
Timings for 2560K FFT length (12 cores, 2 workers):  1.95,  1.91 ms.  Throughput: 1034.34 iter/sec.
Timings for 2560K FFT length (12 cores hyperthreaded, 2 workers):  1.83,  1.82 ms.  Throughput: 1096.38 iter/sec.
Timings for 2560K FFT length (14 cores, 2 workers):  1.86,  1.84 ms.  Throughput: 1080.83 iter/sec.
Timings for 2560K FFT length (14 cores hyperthreaded, 2 workers):  1.65,  1.63 ms.  Throughput: 1216.80 iter/sec.
Timings for 2560K FFT length (16 cores, 2 workers):  1.70,  1.71 ms.  Throughput: 1173.84 iter/sec.
Timings for 2560K FFT length (16 cores hyperthreaded, 2 workers):  1.63,  1.63 ms.  Throughput: 1227.80 iter/sec.
Timings for 2688K FFT length (12 cores, 2 workers):  2.08,  2.04 ms.  Throughput: 971.74 iter/sec.
Timings for 2688K FFT length (12 cores hyperthreaded, 2 workers):  2.02,  2.00 ms.  Throughput: 995.81 iter/sec.
Timings for 2688K FFT length (14 cores, 2 workers):  1.91,  1.94 ms.  Throughput: 1037.88 iter/sec.
Timings for 2688K FFT length (14 cores hyperthreaded, 2 workers):  1.73,  1.73 ms.  Throughput: 1155.66 iter/sec.
Timings for 2688K FFT length (16 cores, 2 workers):  1.78,  1.79 ms.  Throughput: 1119.54 iter/sec.
Timings for 2688K FFT length (16 cores hyperthreaded, 2 workers):  1.74,  1.73 ms.  Throughput: 1154.92 iter/sec.
Timings for 2800K FFT length (12 cores, 2 workers):  2.23,  2.24 ms.  Throughput: 895.77 iter/sec.
Timings for 2800K FFT length (12 cores hyperthreaded, 2 workers):  2.22,  2.17 ms.  Throughput: 910.38 iter/sec.
Timings for 2800K FFT length (14 cores, 2 workers):  2.07,  2.20 ms.  Throughput: 938.82 iter/sec.
Timings for 2800K FFT length (14 cores hyperthreaded, 2 workers):  1.95,  1.93 ms.  Throughput: 1031.45 iter/sec.
Timings for 2800K FFT length (16 cores, 2 workers):  2.22,  2.22 ms.  Throughput: 900.80 iter/sec.
Timings for 2800K FFT length (16 cores hyperthreaded, 2 workers):  1.93,  1.93 ms.  Throughput: 1037.16 iter/sec.
Timings for 2880K FFT length (12 cores, 2 workers):  2.30,  2.29 ms.  Throughput: 870.46 iter/sec.
Timings for 2880K FFT length (12 cores hyperthreaded, 2 workers):  2.37,  2.31 ms.  Throughput: 855.47 iter/sec.
Timings for 2880K FFT length (14 cores, 2 workers):  2.02,  2.18 ms.  Throughput: 954.38 iter/sec.
Timings for 2880K FFT length (14 cores hyperthreaded, 2 workers):  1.92,  1.91 ms.  Throughput: 1044.36 iter/sec.
Timings for 2880K FFT length (16 cores, 2 workers):  1.92,  2.02 ms.  Throughput: 1017.67 iter/sec.
Timings for 2880K FFT length (16 cores hyperthreaded, 2 workers):  1.86,  1.84 ms.  Throughput: 1082.63 iter/sec.