Portable CFD machine - some suggestions needed

flotus1 · July 6, 2018, 07:14

If by "previous generation" you mean the I7-5820k you are out of luck. There are no mini-ITX boards for this processor with 4 DIMM slots. Edit: well except for the ASRock Rack EPC612D4I which takes 4 SO-DIMM modules. But then agian, I don't really see the need to restrict yourself to ITX since you chose a pretty large ITX case. Going mATX would not make for a less portable build, at least I thought that a portable ITX build should be much smaller.
Did you already try to increase memory frequency? That should help a bit with the I7-6700k.

Gerry Kan · July 13, 2018, 16:06

Hallo Flotus,

yes, I was thinking of ASRock Rack EPC612D4I as well ... it's a bit expensive (last time I checked it was 320€) and with the 2011-3 narrow you're basically stuck with a Dynaron cooler (if memory serves, one should come with the MB), which sounds like an airplane taking off. I am actually very curious, though.

From what you said, do you think it is really the fact that I have only dual channel RAMs on the ITX that is slowing down my computations?

I remember when I was setting it up I tried to run the RAMs at 2400 MHz, but the system became unstable, even without overclocking the CPU. I had to throttle it back to 1866 MHz and then the system was stable again.

I also tried to overclock the CPU to 4.4 GHz and I didn't see a noticeable difference in performance, at least for my CFD jobs so I put it back to 4.0 GHz.

Thanks and have a good weekend, Gerry.

flotus1 · July 15, 2018, 09:50

Yes, it is most likely the lack of memory bandwidth that is limiting how fast your computations can run in parallel. Hence my original reservations against an ITX motherboard and slow memory.
With DDR4-1866 your memory isn't even running at the rated speed of the IMC. With a current bios version, basically all Skylake CPUs should be able to handle DDR4-3000 unless your choice of RAM was extremely unfavorable. The memory itself might need a bit more voltage to get there, 1.35V is still perfectly safe for DDR4.

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July 6, 2018, 07:14		#21
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,399 Rep Power: 46	If by "previous generation" you mean the I7-5820k you are out of luck. There are no mini-ITX boards for this processor with 4 DIMM slots. Edit: well except for the ASRock Rack EPC612D4I which takes 4 SO-DIMM modules. But then agian, I don't really see the need to restrict yourself to ITX since you chose a pretty large ITX case. Going mATX would not make for a less portable build, at least I thought that a portable ITX build should be much smaller. Did you already try to increase memory frequency? That should help a bit with the I7-6700k.

July 13, 2018, 16:06		#22
Gerry Kan Senior Member Gerry Kan Join Date: May 2016 Posts: 348 Rep Power: 10	Hallo Flotus, yes, I was thinking of ASRock Rack EPC612D4I as well ... it's a bit expensive (last time I checked it was 320€) and with the 2011-3 narrow you're basically stuck with a Dynaron cooler (if memory serves, one should come with the MB), which sounds like an airplane taking off. I am actually very curious, though. From what you said, do you think it is really the fact that I have only dual channel RAMs on the ITX that is slowing down my computations? I remember when I was setting it up I tried to run the RAMs at 2400 MHz, but the system became unstable, even without overclocking the CPU. I had to throttle it back to 1866 MHz and then the system was stable again. I also tried to overclock the CPU to 4.4 GHz and I didn't see a noticeable difference in performance, at least for my CFD jobs so I put it back to 4.0 GHz. Thanks and have a good weekend, Gerry.

July 15, 2018, 09:50		#23
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,399 Rep Power: 46	Yes, it is most likely the lack of memory bandwidth that is limiting how fast your computations can run in parallel. Hence my original reservations against an ITX motherboard and slow memory. With DDR4-1866 your memory isn't even running at the rated speed of the IMC. With a current bios version, basically all Skylake CPUs should be able to handle DDR4-3000 unless your choice of RAM was extremely unfavorable. The memory itself might need a bit more voltage to get there, 1.35V is still perfectly safe for DDR4.