Best performing setup - with used components
 

Back in the day (may be 5-6 years ago) before I knew about cfd, I built a lga 2011 desktop on the asus p9x79 mb. I still have the rig, writing on it now, while it is running and computing cfd max overclocked. It just runs continuously for months. It has the i7 4820k, 16gb 2400MHz ddr3, running at 4,4GHz, aircooled, with a modest gpu - gtx 760 4gb. I love the machine. Rock steady.

But as thing has progressed I really need more power for the cfd. I need advice for which components to aim for in the used market (ebay etc), mainly thinking of assembling a powerful server from used parts, running whatever OS.

I have to agree, X79 was way ahead of its time.
I assume you are already running the memory in quad-channel? Then you could think about just dropping in the best X79 CPU in your existing system: the 8-core Xeon 1680v2. Despite being a Xeon, it still is fully unlocked. So CPU and memory overclocking work just as with an I7.
The downsides: Your motherboard only officially supports up to Xeon 1650 v2, a 6-core CPU. But there is really no reason why it should not work, and people got it working no problem: https://community.hwbot.org/topic/16...-overclocking/
And then there is the price. The cheapest I can currently find on ebay is 190$. Which is the fate of most "best in slot" parts, they remain unreasonably expensive.

Apart from that, the possibilities are endless. So having some kind of direction would help narrowing down your options.
How much RAM do you need?
Would you be willing to drop some of the awesome single-core performance of an overclocked X79 CPU for significantly higher multi-core performance?
Which software are you using for CFD, and do your licenses have a core limit?

Edit: there is one minor issue with your upgrade plans though...X79 would still be pretty high up there in terms of used price/performance for CFD. At least if it were not for the crazy expensive motherboards these days. Since you already have that part sorted out, getting better price/performance will be difficult.

Wow, what a reply! Thanks flotus1! I've been fixed on the i7 4960X as the only choice for an upgrade, but if the E5 1680 v2 really is compatible with the x79 mb the search is over. After reading up on it, it seems like a bolt on. You just have to know about it. And 200$ is fair, the 4960 is actually slightly more expensive (and slower). It will make my old vanilla Asus p9x79 a Slachtshiff of a workstation. I'll just gonna do it. Thanks!
With this upgrade I have a prima workstation (hopefully for 5 more years, I just cant see why not).
But sooner or later I need an explicit cfd cluster, with significantly more punch. I mean: set up simulations, test them, whatever on the workstation - to process them on some pure hw-rack..

About RAM: I now got 16gb (4x4) kingston hyperx, 2400MHz (OC'd, in quad). The only solution as I see it is to double it up to 32gb. An old cfd "rule of thumb" is 2gb for each core, right?

About SW and license: I am now with Star CCM+, licensed through the university, core limit not an issue for this case. I will be heading for OpenFOAM soon.

About the X79: I thank my background as a dedicated CCM/Football Manager player to head for high performance CPU setups, looong waits behind me ;-) I did not know about cfd when I built it, but it saved my ass in the end.

About the 2011 socket: Since it is discontinued -> good value for money, right? May be it could be my cluster solution as well? As a pure server. Dual xeon (or suchlike (AMD?))?

I see things like this pop up from time to time, but I can not fully subscribe to the concept. Maybe it is supposed to prevent people from combining 64 cores with 32GB of RAM, which could lead to excessive parallelization overhead due to running small cases. But then again, running the same case on 64 cores and 128GB or RAM would not change this.
Get as much RAM as your simulations need, forget about memory per core.
The more important rule of thumb: about 2-3 cores per memory channel, since CFD is hungry for memory bandwidth.

Dual LGA2011 used to be my go-to option back when DDR4 prices were high. With better prices for DDR4 now, you would need to find really good deals on decommissioned cluster nodes to make it worth the overhead. I personally draw the line with Xeon E5-v2. Older than that, and the low efficiency and density make it unappealing to me.
Even new first gen Epyc CPUs should be taken into consideration. A 24-core Epyc 7451 costs around 900€. That still is a lot of money, but a single node with two of these replaces at least two nodes with dual-socket Xeon E5. Forget about AMD Opterons, at least if you have to pay for space, power and cooling.

I guess it all depends on which kind of deals you have access to in your part of the world. And how much you have to pay for electricity.

I have a desktop nearly identical to the OP......

Asus Rampage 4
4820k
Kingston 4x4Gb kit DDR3 @ 2400

.....and it also runs like a champ. My work with CFD (openFoam) is
non professional and only for myself, mostly high subsonic projectiles.
If I were to install a 1650v2, what sort of reduction in running time
would you expect to see when going from 4 cores of 4820 to 8 of 1650?
Depending on the answers I may give it a try.


Ron

I'd say something in the order of 20% reduction in solver time. The Xeon E5-1650v2 has 6 cores, not 8. That's still good value for the money, considering you can sell your old CPU for little less than what the Xeon would cost you.

Excuse the typo Alex, I meant to compare with the 1680.

Ron

I just wait for my 1680 to arrive now, and hope for a straight double up after overclocking. My 4820 scored 11500 on the cpumark @ 4,4GHz, 2400MHz ddr3. Up from 9700 stock. Don't know how good/bad it is, but for my case it must be stable. 4,5GHz was that only for some days... Air-cooled. The 1680 is supposed to achieve 19000 after some tweaking. For the price you get them now - easy choice for me at least.

... and the dropping prices of high quality hardware made me really start looking for some affordable dual cpu server solution.

Sure, FPU throughput will double when upgrading to twice the amount of cores, same clock speed and same generation. Which is what benchmarks like passmark or cinebench are attempting to measure.
But most CFD codes won't scale perfectly up to 2 cores per memory channel. So don't be disappointed if the solver time is not cut in half.

... and it was not :rolleyes: ... but much faster.

The E5 1680 v2 is amazing, but it won't run the ram (HyperX 2400, Kingston) @ 2400MHz with the cpu clocked to 4,2GHz under load, as the i7 4820 did. I only get 2133 -> one second slower (4,1%) for every 5 iterations (3,55M cells, VOF) compared to when running @ 2400 until it crashes. Either the cfd program crashes, or there is a blue screen after about 5 min.

It works fine at idle and whatever, but not under full charge as I need it to. Motherboard: Asus P9X79 (vanilla/entry level).

Cooling: Noctua NH-D14, both fans at full power. Average temp, 100%load, CPUID: 70-72C.

Would it help with better cooling e.g. water? Just found out through web research (got no experience with WC), that the Corsair H115i Pro 240mm wont help much(?).

So the upgrade worked? Good to hear that.
When it comes to memory overclocking, the rules are the same as for CPU overclocking. Not every IMC can get the same results. And from my limited experience with X79, your old CPU must have had an above-average IMC, being able to run quad-channel DDR3-2400.

I don't think better CPU cooling would help much in that regard. And a closed-loop liquid cooler is not significantly better than a Noctua NH-D14 with fans at 100%. You would need a full custom water cooling, which kind of defeats the price/performance theme of this upgrade.

I assume you are already familiar with how to overclock your system ;)
If you need a refresher, here is a quite thorough guide: https://forums.overclockers.co.uk/th...uide.18476907/
The voltage most relevant to overclocking memory, aside from memory voltage itself, is VCCSA.
Or you could try a 125 strap to see if you can get at least DDR3-2333 working.