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Recommendation to buy a workstation 2017

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Old   February 2, 2017, 12:03
Default Recommendation to buy a workstation 2017
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Hello everyone

I am working with a university, which has a good amount of money to buy a workstation. Our intention is to simulate in ansys fluent or in any powerful software. I want your recommendation what workstation we should buy.

Please can you write the features of the workstation that we should buy. We are seeking a really high performance.

Thank you

PD: I have read some other post but the majority are old.
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Old   February 9, 2017, 07:12
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Hi everyone,

since I'm in a similar situation, I'd like to add few things to this question. In my work, I'm considering the use of AVL Fire software. Ansys Fluent is also an option. I'll be needing to simulate sistems having eventually probably cca 5 mil cells, the number can quickly go up to 10 (geometry not defined completely yet). Since I'll be looking into combustion simulations (time step of order of seconds, low to medium turbulent flow), I'm wondering if an i7 CPU (6700) will be enough for practical work.

I'm guessing 32GB of RAM will be enough, 256-512GB+1/2TB SSD&HDD for running and storing. Discrete GPU (nVidia quadro K2200) should be ok.

I'd like to ask if you'd have some suggestions on using either the i7 or trying to get a dual Xeon (E5) for such kind of tasks and increase amount of cores. Would you then also have any suggestions on the motherboard and RAM which would be better for the dual Xeon?

Also, has anyone any kind of experience with running AVL Fire in parallel? I reckon the licences should not be a problem, but since I don't seem to get any specs for Fire so quickly as for Fluent, I'd ask if my assumption that Fire is similar to Fluent regarding running in parallel is sound? For fluent, there are comments that 100 000k cells are usually the way to go when you want efficiency and practicality but I'm afraid I'll have to eventually go higher than that and pay the price in longer time per time step...Also, what about hyperthreading and parallel simulations-Fluent seems to be better if this is turned off. Would anyone have comments on Fire and this matter?

thanks in advance!
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Old   February 12, 2017, 07:30
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Quote:
I'm wondering if an i7 CPU (6700) will be enough for practical work
Impossible to answer this question. Depends on how long you can wait for your simulation result. And if your models fit within the 64GB memory limit. Which they should with only 10 million cells.
btw: The I7-7700k replaced the I7-6700k a while ago.

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I'd like to ask if you'd have some suggestions on using either the i7 or trying to get a dual Xeon
This is not a binary decision. Somewhere in between the two options is a single-CPU 2011-3 platform. Which one is the best for you depends on your budget and if you want ECC memory or not.

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I'd ask if my assumption that Fire is similar to Fluent regarding running in parallel is sound?
I am not using AVL Fire, but for all I know your assumption is correct.

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For fluent, there are comments that 100 000k cells are usually the way to go when you want efficiency
You got this one mixed up. 100k cells per thread is a very rough rule of thumb. With a smaller amount of cells per thread, parallel efficiency decreases significantly. Of course you can use more than 100k cells per thread, you actually gain parallel efficiency.

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Also, what about hyperthreading
Turn it off or at least do not use more threads than physical cores.
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Old   February 12, 2017, 08:43
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thanks for the advice!

since I posted the questions, I've spent some time searching for what might work for me. I've really not known very well what exists out there regarding the CPUs now anyway, I've leaned towards i7 6800k. It offers me 6 cores and better performance than 7700k despite lower core frequency. On the other hand, I don't think I can go to dual 2011-3 configuration with xeons, the price vs gain does not seem plausible.

but I got worried now when you mentioned 64GB, if the model will fit into this. Upon checking what people say about RAM and amount of cells, I came to suggestions 1-2 mil cells per 1GB of ram are the rough estimates. it then depends on your models too. and here's the tricky bit for me, since I'll be doing combustion stuff, with lots of modelisation included. I leaned to 32GB which would seem enough for 10 mil cells regarding the 2mil/GB estimate, but your mentioning of 64GB got my attention-would you say that this would be needed? since if it's not going to be used, quite some money will be spent on a part not to be used. But anyway...the motherboard has 8 slots, I've went for 4 x 8 GB for now (apparently better than 2x16 because of quad channel, please correct if wrong) just so that I can add 4x8GB later...

also-since I see you're the proper address for harware questions here, two more questions
-would the quadro k1200 graphic card be a good one, or should I go for k2200? or what would your suggestion be, in the $$ range of these cards?
-for i7 6800k intel says that ddr4 with 2400MHz is the correct one. Is there maybe any play or gain if I choose higher frequency, since I see people saying higher freq can be chosen...

thanks again!
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Old   February 12, 2017, 09:44
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I mentioned the 64GB memory limit for Kaby Lake processors in a more general sense. I am pretty sure that with the simulations you described, starting with 32-64 GB (depending on how tight your budget is) and 4 free slots for future upgrades is reasonable. You can add 32GB or 64GB later, 96GB of total memory in quad-channel mode are possible when the DIMMs are populated correctly.

Concerning the graphics card, a Quadro K1200 4GB for ~280$ should do it. At least the K2200 is not much of a performance upgrade and costs almost twice as much.
My latest workstation has a GTX 1060 6GB which offers a much better price/performance ratio. But only because I made sure that I don't need any optimizations Quadro drivers offer for some professional softwares. Ansys claims that their software runs better with Quadro cards. I have no possibility to verify their claims and they do not back them up with some actual benchmarks. So using a Quadro card is a somewhat safe option because you do not need high GPU performance anyway.

DDR4-2400 is the maximum memory speed Intel guarantees for their Broadwell-E processors, that much is true. However, I would recommend buying DDR4-3200. It does not cost that much more money and usually runs runs without a problem thanks to the XMP profiles. If you should ever have trouble you can still run it with lower frequencies.
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Old   February 12, 2017, 09:53
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some nice answers for me right there thanks!
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