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Old   June 12, 2017, 07:16
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Originally Posted by tombo View Post
I don't have too much faith in that benchmark as far as AMD CPUs go. I'm finding the single core performance slightly better than Broadwell (for the same clock speed) for reasonable size cases (>10M cells), but that the scaling isn't that impressive to 8 cores with the AMD. Not terrible, but definitely not as good as the intel CPUs I have access to (which are quad channel or dual cpu quad channel).

AMD have just released an extension to the Clang compiler specifically for RYZEN so it'll be interesting to see if that makes any difference. I am getting best performance with OpenMPI (compared to intel and platform) but it is marginal.
So would you recommend this setup over a equivalently priced intel setup?
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Old   June 12, 2017, 08:48
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The R7 1700 is pretty good value, it comes with a stock cooler than handles a reasonable overclock, and works with the cheapest motherboards. At this price point it's comparing to mid-to-high end 4 core, 8 thread intel CPUs, also with 2 channel memory. If this is your budget, then I'd say the 1700 is the best bet currently.

The next step up is the X99 platform. To get a decent jump in performance over the 1700 I'd be going past the 6 core options to the 6900K or better. With quad channel memory that's going outperform the R7 without any doubt, at a price.

There is a lot of new stuff coming out in the next few months, including the X299 platform from intel and the X399 platform from AMD. I think it's highly likely that we'll see a 'mainstream' grade intel with at least 6 cores before too long.
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Old   June 13, 2017, 04:47
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I will wait for the new x299 and x399 solutions, but as a hobbyist in CFD (is there even such a thing?) I think financially the 1700 makes the most sense.
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Old   July 17, 2017, 17:29
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@tombo, you were right; the 6 core intel CPU arrived. It is based on the lga1151 socket, so hopefully, the price will be mainstream https://www.cpchardware.com/coffee-lake-approche/

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Old   October 17, 2017, 22:31
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Could anybody tell if CL 8700K (Double channel mem) would be better than a 6800k (four channel mem) for OpenFOAM? Would the higher frequency compensate the memory channels?.

I don't know if cannonlake or Icelake will be four channel and/or affordable

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Originally Posted by xava View Post
@tombo, you were right; the 6 core intel CPU arrived. It is based on the lga1151 socket, so hopefully, the price will be mainstream https://www.cpchardware.com/coffee-lake-approche/

Last edited by pibil1; October 18, 2017 at 11:30.
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Old   October 18, 2017, 04:58
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CFD performance is application dependent, that is rankings can change according to the solver in use. Having said that, I have seen a benchmark that ranked a stock 8700K performing at about 90% of the performance of a 6900K. That'd make it very close to the 6800K.

My experience with the R7 1700 indicates that it's pretty pointless going for more than 6 cores with dual channel. My rule of thumb is 3 cores per memory channel and that seems to work across most platforms.

It looks like a really good CPU - it overclocks well and has supports fast RAM.
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Old   October 19, 2017, 07:08
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Originally Posted by pibil1 View Post
Could anybody tell if CL 8700K (Double channel mem) would be better than a 6800k (four channel mem) for OpenFOAM? Would the higher frequency compensate the memory channels?.
The four memory channels will have much more bandwidth than a dual memory channel. It has 2x the memory channels, where the memory clock is 90% of that of the 8700K. CFD is memory bandwidth limited, and on large models using double precision, I lose linear speedup (due to memory bandwidth becoming a bottleneck) going from 3 to 4 cores. 4.2GHz 4930K CPU with Quad channel 2133MHz RAM. So It looks more like 1 core per memory channel is the most efficient, and bottlenecking becomes noticeable past that.
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