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Old   May 26, 2018, 18:11
Default Budget desktop/workstation build
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First I would like to describe the initial problem that has led to me deciding my current i3-3230M lenovo laptop is no long sufficient for my computing needs. I am an undergraduate aerospace engineering student at my local state university and I am working on my senior design project. We are building a small(about 4.5 kg) RC UAV for the project and my faculty advisor/supervisor for the project wants to see an Ansys 3d CFD fluid analysis of the UAV.

I have checked and there is a student license for Ansys which has the following limitations:
500k mesh elements
16 cores maximum can be used to solve

Additionally further on down the line I would like to design my own small turbo-shaft engines as a side project. My target power output for these engines will be in the 100-150KW range to give you an idea of their size. If the design is successful I hope to use them in another much more involved project. I will almost certainly want to do CFD analysis on these and will most likely use OpenFOAM or a similar free/open-source CFD tool for that so as to not be limited or burdened by license limits or costs.

This machine will also be used as my general everyday home computer for everyday stuff as well as solidworks CAD for school when not being bogged down with a CFD problem. When it is running a CFD problem I still have my old lenovo laptop that is capable of doing everything else I foresee myself doing in the near future.

From my research it would seem that one of the major bottlenecks for CFD work is the memory bandwidth, especially once the processor reaches sufficient power to meet or exceed the speed of information that the memory bandwidth can supply. More specifically it seems that the "sweet-spot" for this is somewhere in the neighborhood of 2 CPU cores per memory channel, provided those cores are of sufficient clock speed, and that anything over this results in serious diminishing returns for use of additional or faster cores. However CFD is also very highly threaded and does benefit from having lots of cores provided the memory bandwidth doesn't become a bottleneck limiting the ability of these cores. To that end it seems that my best option is to have as many cores as I can afford as long as I increase memory bandwidth appropriately as I go up in core count.

My budget for this build is in the approximately 2,000 USD range, if I go over this slightly in order to build a much better machine that is ok. I am most likely going to be assembling the machine from parts myself as it seems I can get a lot more computer for my money this way and I am quite sure I am capable of it.

With all this in mind it seems my options have come down to 2 processor and chipset combinations in order to achieve the maximum core count with the fastest possible cores while still maintaining a 2 core per memory channel ratio. These choices are:
1) Intel i7-7820X (8 cores, 4 channels of DDR4 memory) with an X299 chipset motherboard
2) AMD Ryzen Threadripper 1900X (8 cores, 4 channels of DDR4 memory) with an X399 chipset

The rest of the components should be pretty much identical regardless of which chip I choose and they will most likely be along the lines of this:
Graphics: Nvidea GTX 1060 6GB
Storage: 512GB SATA SSD or possibly a PCIe SSD
Ram: 4x8GB DDR4 ram for 32GB 4 channel memory
A power supply sufficient to power everything with decent headroom above the minimum need
A case to that fits everything with good ventilation
Good cooling
and likely and DVD/CD-RW optical drive

My questions to you all are:

1) Does this build seem sufficient for what I will need to do with it?
2) Between the Intel and the AMD which processor would you recommend and why? I am personally leaning more towards the Intel as it seems to score higher in all of the benchmarks I've seen but none of those are CFD specific benchmarks.
3) Is the memory bandwidth as important as I believe it to be? Stepping down to either the Ryzen 7 or coffee-lake mainstream chips will grant similar CPU power but half the memory bandwidth at only 2 channels of memory
4) Along the lines of question 3, would it be worth potentially considering the threadripper 1920X 12 core processor or would it simply be choked by still only having 4 memory channels and not worth the additional cost?
5) Am I correct in my belief that stepping up to a server grade chip such as the Epyc or Xeon will put me way over budget? I have looked and while these processor lines both seem like they would provide much faster CFD run times their costs both for the chip itself as well as associated components seems to be much higher, especially for the specific models that would provide significant improvements.

Thank you all for your time and insight.
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Old   May 29, 2018, 07:30
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Have you read our sticky thread? OpenFOAM benchmarks on various hardware
It contains quite a few benchmarks for various hardware configurations.

Quote:
1) Does this build seem sufficient for what I will need to do with it?
Sure, no matter which option you choose.
Quote:
2) Between the Intel and the AMD which processor would you recommend and why? I am personally leaning more towards the Intel as it seems to score higher in all of the benchmarks I've seen but none of those are CFD specific benchmarks.
If you get really fast memory (in the range of DDR4-3600 or higher) and tweak the CPU a little bit, an I7-7820X can be significantly faster than a Threadripper CPU. If you run everything @stock the difference is pretty small and it comes down to personal preference.
Quote:
3) Is the memory bandwidth as important as I believe it to be? Stepping down to either the Ryzen 7 or coffee-lake mainstream chips will grant similar CPU power but half the memory bandwidth at only 2 channels of memory
Yes it is. Stepping down to an I5-8600k would yield better single-threaded performance, but significantly less parallel performance than those 8-core CPUs with quad-channel memory interface. But of course it is much cheaper...
Quote:
4) Along the lines of question 3, would it be worth potentially considering the threadripper 1920X 12 core processor or would it simply be choked by still only having 4 memory channels and not worth the additional cost?
Definitely not worth it.
Quote:
5) Am I correct in my belief that stepping up to a server grade chip such as the Epyc or Xeon will put me way over budget? I have looked and while these processor lines both seem like they would provide much faster CFD run times their costs both for the chip itself as well as associated components seems to be much higher, especially for the specific models that would provide significant improvements.
All decent current gen Xeons are way too expensive and have a hard time outperforming an I7-7820X that has been tweaked a little.
The only somewhat viable option would be an Epyc 7351P. But it is quite expensive, requires an expensive motherboard and at least 8 DIMMs. I would stick with an I7.

Another option might be an older dual-socket 2011 platform. This could get you 2x8 or 2x10 cores with plenty of memory for ~2000$.
More info here: Dual E5-2680 V2 workstation advice
And here: https://forums.servethehome.com/inde...d-build.18412/
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Old   May 30, 2018, 17:15
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So based on what I already know as well as your response I am going to stick with the plan of the i7-7820x. This will also be a general purpose desktop PC as well so I want decent single thread performance also in addition to multi-threaded and this seems like the best all round choice, especially once considering budget.

I will most likely order this PC from one of the custom resellers as I found one with good ratings that seems to have reasonable prices. I'm not opposed to building it myself if the savings are significant but I'd rather avoid the hassle if the cost is similar or only slightly more.

How do these specs look for everything?

Tower Case: Phanteks Eclipse Series P400S, No PSU, E-ATX, Black, Mid


Motherboard: ASUS TUF X299 MARK 2, Intel X299 Chipset, LGA 2066, ATX Motherboard


Processor: INTEL Core™ i7-7820X 8-Core 3.6 - 4.3GHz Turbo, LGA 2066, 140W TDP, Processor


Video Card: EVGA GeForce GTX 1060 SC GAMING ACX 2.0, 1607 - 1835MHz, 6GB GDDR5, Graphics Card [VR-Ready]


Memory: KINGSTON 32GB Kit (4 x 8GB) HyperX Fury DDR4 2666MHz, CL16, Black, DIMM Memory


Power Supply: SEASONIC SSR-850PX, 80 PLUS Platinum 850W, Fully Modular, ATX Power Supply


CPU Cooler: Special NOCTUA NH-D15S, 160mm Height, 220W TDP, Copper/Aluminum CPU Cooler


SSD Storage: SAMSUNG 500GB 860 EVO 7mm, 550 / 520 MB/s, V-NAND MLC, SATA 6Gb/s, 2.5-Inch SSD


Is there anything about this build that sticks out as wrong? Anything way above or below what I would want/need in comparison to the other parts? Anything that is known to be a low quality part? Anything that would be way overpriced compared to a similar equivalent part from another brand/manufacturer?
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Old   May 30, 2018, 18:02
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The CPU cooler is a good choice, but it could be a very tight fit with this case. I would rather change the case than the cooler
For the motherboard I recommend ASRock X299 Extreme 4. It has everything an X299 motherboard needs and saves a few bucks that are better spent on different components. For the absolute best performance, a motherboard with only 4 DIMM slots total (like most mATX boards) would offer a slight advantage. With the drawback of 64GB maximum RAM. Since your models seem to have a very low cell count, you might consider it.
And as usual: Either choose faster RAM in the first place or be prepared to do some manual overclocking on the RAM. Using DDR4-2666 would be a waste for this expensive PC. The platform has proven to run DDR4-3600 and even beyond. Get dual-rank modules if possible.
850W is more than enough to power this build. The same PSU with 750W still has the second 8-Pin EPS connector that some X299 motherboards have.
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Old   May 30, 2018, 19:56
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The computer builder's website shows that cooler as compatible with this case. If I change the option to the very slightly larger d15(without the s) at 165mm instead of 160mm it gives a warning that it is not compatible with the case. So it seems it will in fact fit, but is also the largest cooler that will and thus yes it will be a tight fit but it should fit. I'm not married to the case though, that was just the default case option for their "quite workstation" build. What other cases would you recommend? I don't care about glass windows or RGBs or any of that fancy "gamer" stuff. I do care that it has good airflow while preferably also being quiet, or at least as quiet as possible for this level of performance as I realize those two things tend to be mutually exclusive.


Regarding the motherboard, I selected the ASUS because the TUF board is supposed to be built for reliability and I read they ASUS was supposed to have the best audio. Looking at the specs the audio is similar between the 2 though, the asus might have slightly better but not a big enough difference that I think I would notice. I'm also now noticing that neither supports wifi or bluetooth on the board itself, not a huge deal since I will have it hardwired to the router most of the time, but it would be nice to have it if it's ever needed. They sell USB fobs for that though. The ASrock is about 45 bucks cheaper.

Regarding the RAM I was going for the 2666 MHz because that was the speed that intel says that the 7820x supports. I wasn't really trying to get into overclocking and faster ram is more expensive. I'll have to see how big the price difference is and think about it.

As far as only have 4 RAM slots, I don't think I want to do that unless the speed advantage is large. I would like to have the maximum expand-ability to add up to the maximum that the CPU supports in case I ever do more memory hungry work in the future. That is unless the performance boost from only 4 slots is significant, but you said it was slight.

Edit: Regarding the case, what do you think of the Fractal Designs Meshify C? It's a little shorter and not as long as the Phanteks but it's wider to allow for more room for the CPU cooler. It also has an angled mesh in front instead of a solid panel so it seems this will help facilitate good airflow through the case, also I personally think it looks cool.

Last edited by Cavitated; May 31, 2018 at 02:07. Reason: Added question regarding different possible case option.
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Old   May 31, 2018, 10:13
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The cheapest 4x8GB DDR4-2666 is around 290€ here. The same amount of DDR4-3600 starts at 340€.
Considering what the whole system costs, that is around 5% more money for 20-30% more performance. Hard to get such a great value with any other component. "Overclocking" is as easy as activating Intel XMP in the bios. A few clicks, reboot, done.
Thanks to the ridiculously high RAM prices in general, the premium for faster RAM is not as high as it used to be.

Fractal Design Meshify C will work. It only comes with 2 fans, get 2-3 extra fans to keep the noise level and temperatures low. Or replace the fans completely if you want it extra quiet.

Built-in Wifi can only be found on the more expensive boards. A PCIe-card or a USB adapter fix this for much less $.
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Old   May 31, 2018, 14:56
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So given the price difference being small I agree that I should go with faster ram. Also the ASrock seems to effectively have roughly all the same features as the asus, certainly all the features that I can think I will need, and is reviewed as well if not slightly better than the asus so that seem like a good option, especially being cheaper. The power supply is all about having enough power with a decent margin above for potential upgrades/changes and safety factor while being quality and efficient so there is no need to go needlessly overboard on the wattage. So having taken your advice on many points here is the current configuration I am looking at:

Tower Case: Meshify C, No PSU, ATX, Black, Mid Tower Case (this might still change)



Motherboard: ASROCK X299 Extreme4, Intel X299 Chipset, LGA 2066, ATX Motherboard


Processor: INTEL Core™ i7-7820X 8-Core 3.6 - 4.3GHz Turbo, LGA 2066, 140W TDP, Processor


Video Card: EVGA GeForce GTX 1060 SC GAMING ACX 2.0, 1607 - 1835MHz, 6GB GDDR5, Graphics Card [VR-Ready]


Memory: KINGSTON 32GB Kit (4 x 8GB) HyperX Predator DDR4 3200MHz, CL16, Black, DIMM Memory


Power Supply: SEASONIC SSR-750PX, 80 PLUS Platinum 750W, Fully Modular, ATX Power Supply


CPU Cooler: Special NOCTUA NH-D15S, 160mm Height, 220W TDP, Copper/Aluminum CPU Cooler


SSD Storage: SAMSUNG 500GB 860 EVO 7mm, 550 / 520 MB/s, V-NAND MLC, SATA 6Gb/s, 2.5-Inch SSD

I have looked at other cases and most of the smaller ones all only come with 2 fans while some of the larger(and more expensive) ones include 2 front fans and 1 rear for 3 total. The larger ones also tend to include/support larger fans as well though. The Fractal Design Define R6 seems like it might be a good alternative option with 3 fans instead of 2, and having 140mm fans instead of 120mm. It is about 60 bucks more expensive and draws intake air from side vents instead of a nice large front mesh though. The be quiet silent base 800 also includes 3 fans but is 100 bucks more expensive and the rear exhaust fan is still only 120mm. So I'm currently leaning towards either just adding a 2nd intake fan to the meshify or going with the R6.

Regarding ram 3200 MHz is the highest speed that the PC builder I'm currently looking at offers, it does not look like dual rank ram is an option at all. How much faster is dual rank anyway? Is it a major boost or only a slight one?
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Old   November 15, 2018, 06:46
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Trying to understand the importance of maximum bandwidth here; given somewhat similar CPU frequency, would a doubled bandwidth also lead to halfed solution time? I'm considering a used workstation.



Here's the current laptop and proposed CPU's in question: https://ark.intel.com/compare/97463,76161
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Old   November 15, 2018, 12:31
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Quote:
given somewhat similar CPU frequency, would a doubled bandwidth also lead to halfed solution time? I'm considering a used workstation.
Yes, under the following assumptions: same core count, same CPU architecture/generation and a workload that is still fully bandwidth limited on the CPU with twice the memory bandwidth available.

That being said, the Xeon E5-2687W v2 is without a doubt the better CFD processor. But if you buy used, the Xeon E5-2667v2 is the better choice because it is cheaper and has almost identical specs.
Another caveat: those Xeon E5-2xxx CPUs are for dual-socket operation. You can still use them in single-socket systems, but there is usually a better aka cheaper alternative. Xeon 1650v2, 1680v2 (not really cheap) or some I7 CPU for the same socket.
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Old   November 15, 2018, 12:45
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Would the bandwidth be limited if processors runs on 100% load? Or are there other means to check this?


For the record, I'm looking at a used workstation with two Xeon E5-2687W v2, and not buying these separately. So I have to go for the whole deal, or buy separate cpu's extra. But so far it looks like a fair deal.
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Old   November 15, 2018, 13:08
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If the operating system reports 100% load on all cores this does not even indicate that the CPU is fully utilized. And it allows no assumption on memory bandwidth usage. Without your own code that you can analyze or instrument for measurements, finding memory bandwidth utilization is not straightforward.
You could run a core scaling analysis, but without knowing what the code actually does this can lead to wrong conclusions.

FYI: this was one of the CFD workstations I put together with CPUs from the same gen. Total cost for parts was around 2200€
https://forums.servethehome.com/inde...d-build.18412/
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