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Alder lake mobile cpu for cfd or upgrade older desktop?

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Old   October 11, 2022, 20:22
Default Alder lake mobile cpu for cfd or upgrade older desktop?
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Hello everyone,

I am waiting to buy a laptop because it's midterm season and I am in the process of applying to a student formula-e team.

However hoping that I do make it through, this would decide my purchasing decision.

So my school has used ansys fluent but wants to move to openfoam, so likely will be running both or a ratio of each.

My desktop is an x99 i7 5960x with 16gb ddr4 2133mhZ ram. Now most benchmark shows the new mobile alder lakes and even amd beat my desktop, however none of that shows potential cfd performance. I'm wondering if it's worth buying a cheaper laptop and buying 3300mhz 64 gb kit for my desktop will be a better idea ? The team historically runs RANS and then DES simulation of their car and aero kit.

The new ram should allow me to overclock as well. So is it a good option or is it better to get a balls to the wall alder lake laptop?

Thanks
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Old   October 12, 2022, 01:28
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If you can get 3000 MHz on a memory overclock of your desktop with four channels your performance on the benchmark: OpenFOAM benchmarks on various hardware should be quite good. I estimate just over 100 seconds to complete. For comparison: Threadripper 5995wx workstation completes in 40 seconds.
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Old   October 12, 2022, 04:07
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Close to 100s seems a bit optimistic for ye olde i7 5960x, even with fast memory. It was a good CPU, but not that good.
OpenFOAM benchmarks on various hardware
There are quite a few comparable HEDT CPUs in this thread that are in the 150-170s range, with DDR4-3000+

You can get similar or a bit faster run times with a modern laptop. Provided it has proper dual-channel DDR5 memory.
So it comes down to preference. Do you want a dedicated machine for CFD, i.e. being able to use your laptop while the old I7 solves your CFD models. Maybe you care about power consumption, which will certainly be higher with an overclocked I7-5960X running DDR4-3200 memory. And an Alder Lake laptop CPU will outclass the I7-5960X in anything lightly-threaded. Like pre- and post-processing, tasks where you probably sit in front of it and have to wait until it finishes.
It's up to you, the performance of both solutions for the solver phase can be in the same ballpark.
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Old   October 12, 2022, 16:17
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The older 5960x may outperform the 7820x because the L3 cache is almost twice as large: 20 MB Intel® Smart Cache versus 11 MB L3 Cache. Still, 160 seconds would not be bad.


My method of estimating is to compare an overclock to 5.6 GHz with 3200 MT/s memory to a dual E5-4627 v2 system at 3.6 GHz using 1600 MT/s memory (but double the total memory channels.) This system dual v2 does the benchmark in 113 seconds. You might not quite get there, because you have less cache and half the cores, but somewhere in between 113 and 160 seconds seems the likely outcome.


If you have the time, you can try the benchmark on your desktop as is. You should expect something like 240 seconds on 8 cores.


I think a cheap upgrade on your desktop now and a laptop purchase later is preferred, because you would want a DDR5 laptop. These laptops are sure to come down in price in the coming year.
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Old   October 12, 2022, 23:32
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Quote:
Originally Posted by wkernkamp View Post
The older 5960x may outperform the 7820x because the L3 cache is almost twice as large: 20 MB Intel® Smart Cache versus 11 MB L3 Cache. Still, 160 seconds would not be bad.


My method of estimating is to compare an overclock to 5.6 GHz with 3200 MT/s memory to a dual E5-4627 v2 system at 3.6 GHz using 1600 MT/s memory (but double the total memory channels.) This system dual v2 does the benchmark in 113 seconds. You might not quite get there, because you have less cache and half the cores, but somewhere in between 113 and 160 seconds seems the likely outcome.


If you have the time, you can try the benchmark on your desktop as is. You should expect something like 240 seconds on 8 cores.


I think a cheap upgrade on your desktop now and a laptop purchase later is preferred, because you would want a DDR5 laptop. These laptops are sure to come down in price in the coming year.
How do I run the benchmark on my current system ? I assume I need more than 16 gb ram?

I was thinking of doing a mild upgrade to desktop too.
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Old   October 12, 2022, 23:35
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Quote:
Originally Posted by flotus1 View Post
Close to 100s seems a bit optimistic for ye olde i7 5960x, even with fast memory. It was a good CPU, but not that good.
OpenFOAM benchmarks on various hardware
There are quite a few comparable HEDT CPUs in this thread that are in the 150-170s range, with DDR4-3000+

You can get similar or a bit faster run times with a modern laptop. Provided it has proper dual-channel DDR5 memory.
So it comes down to preference. Do you want a dedicated machine for CFD, i.e. being able to use your laptop while the old I7 solves your CFD models. Maybe you care about power consumption, which will certainly be higher with an overclocked I7-5960X running DDR4-3200 memory. And an Alder Lake laptop CPU will outclass the I7-5960X in anything lightly-threaded. Like pre- and post-processing, tasks where you probably sit in front of it and have to wait until it finishes.
It's up to you, the performance of both solutions for the solver phase can be in the same ballpark.
I'd ideally want to run most of the cad and simulation on my desktop with some light RANS and test runs on my laptop. I'd love a used workstation but the octa channel ones cost alot and it seems regular threadripper isn't a good choice.

Anyway, I'd like both my laptop and desktop to be capable, but if a laptop out performs my desktop then I don't know if it's worth sinking more money into it.
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Old   October 13, 2022, 00:15
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Quote:
Originally Posted by EternalSeekerX View Post
How do I run the benchmark on my current system ? I assume I need more than 16 gb ram?

I was thinking of doing a mild upgrade to desktop too.

The benchmark runs in about 7GB I think.


You can go here (press on ">") for the benchmark files:
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Here it is. Run it with run.tst The file has a list of numbers of nodes at the beginning. A little further down you can set prep=0 to avoid recalculating the mesh if you already have a valid mesh. In the loop for running openFOAM itself, I remove the simpleFoam log files, etc to allow a rerun to proceed. On the first try, these files are not there yet, so you see an error message that you can ignore.

If you have a problem running the benchmark post a question back here.
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Old   October 13, 2022, 04:29
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Quote:
Originally Posted by wkernkamp View Post
My method of estimating is to compare an overclock to 5.6 GHz with 3200 MT/s memory
Typo? 5.6GHz on an I7-5960X is LN2 territory. Something in the 4.5GHz range might be doable with custom water cooling, if you don't care about power consumption at all.
03-leistungsaufnahme-volllast-cpu-(gesamtsystem)-chart.png
Diminishing returns with higher CPU clock speeds strike as well. Increasing uncore frequency will get you further, but also is a huge contributor to the heat load.

Same with memory. DDR4-3200 on this CPU is relatively straightforward with 4x single-rank DIMMs. For 64GB+, you are using 2 ranks per channel, which some CPUs might just not be capable of at 3200MT/s. And if they are, it requires increasing various other voltages. Leading to even higher power consumption.
I once had a system with the little brother of this CPU, a Xeon E5-1650v3. It was great fun to play around with, but power consumption and cooling requirements quickly go through the roof if you push it.
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Old   October 17, 2022, 10:49
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My desktop workstation still runs a i7-5960x; it was quite ahead of its time for a desktop-grade CPU for CFD. But it's half as fast as a Ryzen 5950x for CFD (even overlocked to 4 Ghz all-core), while drawing like twice the power, so it's about time to put her out to pasture.

A colleague tried to run CFD on a newer workstation-grade laptop recently, and it worked reasonably well. But laptop cooling solutions are really not designed for the sustained loads produced by CFD (especially on the SODIMMs), and it was throttling a lot.

I'll repeat my usual 'budget CFD workstation' recommendation of a used EPYC Rome workstation with 2-4 cores per memory channel (16-32 cores per socket), and make sure it's running 3200 MT/s RAM with every DIMM slot populated. Your $ will go a lot farther that route than trying to run CFD on a laptop or upgrading an ancient Haswell workstation.
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Old   January 11, 2023, 03:02
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Quote:
Originally Posted by wkernkamp View Post
The benchmark runs in about 7GB I think.


You can go here (press on ">") for the benchmark files:



If you have a problem running the benchmark post a question back here.
Hey sorry for the late reply, but when I run the script file, it runs the case.with default mesh, I don't see it trying the higher mesh count run
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Old   January 11, 2023, 03:08
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Originally Posted by flotus1 View Post
Typo? 5.6GHz on an I7-5960X is LN2 territory. Something in the 4.5GHz range might be doable with custom water cooling, if you don't care about power consumption at all.
Attachment 91910
Diminishing returns with higher CPU clock speeds strike as well. Increasing uncore frequency will get you further, but also is a huge contributor to the heat load.

Same with memory. DDR4-3200 on this CPU is relatively straightforward with 4x single-rank DIMMs. For 64GB+, you are using 2 ranks per channel, which some CPUs might just not be capable of at 3200MT/s. And if they are, it requires increasing various other voltages. Leading to even higher power consumption.
I once had a system with the little brother of this CPU, a Xeon E5-1650v3. It was great fun to play around with, but power consumption and cooling requirements quickly go through the roof if you push it.
Quote:
Originally Posted by the_phew View Post
My desktop workstation still runs a i7-5960x; it was quite ahead of its time for a desktop-grade CPU for CFD. But it's half as fast as a Ryzen 5950x for CFD (even overlocked to 4 Ghz all-core), while drawing like twice the power, so it's about time to put her out to pasture.

A colleague tried to run CFD on a newer workstation-grade laptop recently, and it worked reasonably well. But laptop cooling solutions are really not designed for the sustained loads produced by CFD (especially on the SODIMMs), and it was throttling a lot.

I'll repeat my usual 'budget CFD workstation' recommendation of a used EPYC Rome workstation with 2-4 cores per memory channel (16-32 cores per socket), and make sure it's running 3200 MT/s RAM with every DIMM slot populated. Your $ will go a lot farther that route than trying to run CFD on a laptop or upgrading an ancient Haswell workstation.
Thank you both for your responses, I am officially on the f1 team doing some work on front wings. Anyway they use mechanical for fea and openfoam for cfd. In addition I'm doing a side research with some professors that have us use fluent with no core limit as well. So I will be using both software it would seem. We do have access to a cluster (but it seems busy and it looks like PhD students always fight for cluster time).

I am considering building a purpose built system for just this type of workload (maybe even have a windows vfio for solidworks and other windows applications). I am in the Canadian market, however based on some threads here, it would seem even some older eypc aren't that good ? It's quad channel really considered bottom of the barrel now? It would also seem the used server market is not that attractive for Canadians lol.

Thanks
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Old   January 11, 2023, 03:32
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It's quad channel really considered bottom of the barrel now?
Pretty much, yes. Not necessarily because these CPUs are trash. But because you get much better value from current-gen desktop CPUs with DDR5.
This likely won't change in the future, if Intel or AMD decide to release new HEDT CPUs. They will aim for high core count, not good value with moderate core count.

For a DIY system on a limited budget, it's either a modern desktop CPU with fast DDR5 memory. Or used server stuff like Epyc Rome if you need more performance. I don't really see any platforms between these two extremes.
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