The choice of GPU(s) is the most important consideration.
While CPU performance is significant for GPUGrid, the more GPU's you have the more the motherboard becomes important. There are many architectures to chose from today and performance does not change much across several (i7-9xx, i7-8xx, i7-2000, i7-3900). AMD have a sizable range too, but performance is generally lower. System RAM speeds and amount tend not to make much of a difference for GPUGrid, so don't overly invest there. Ditto for the HDD.

The GPU (CC2.0/2.1), CPU and PSU are key to power and efficiency.
The SB processors offer excellent performance for their power consumption (stock ~65W crunching flat out). A mildly overclocked i7-9XX (to match the SB performance) is likely to use ~130W, which might push your PSU requirements up a notch. On the other hand a good 1366 board could support more than two GPU's at reasonable PCIE levels, and also offers triple channel RAM and more CPU threads.
In terms of crunching, it's been repeatedly demonstrated that the performance of the i7 3960X is no better than an i7-980. So at present the only benefits of these overly expensive systems is reduced power requirements and support for PCIE3, which is supposedly limited to a few recent boards, and as yet not for any NVidia GPU...

PCIE 3 X8 is as fast as PCIE 2 X16 if you can use it, but PCIE3 won't be usable at GPUGrid until a Kepler turns up, or we start using AMD's most recent GPU's and then only on the expensive LGA2011 systems.

I bought a similar board as Damaraland (Z68A-G45), partially because I like MSI/dislike others, but mostly because at the time MSI were the only company locally selling a 'potentially' PCIE3 future proofed LGA1155 mother board. I never expected to see PCIE3 performances with my GTX470; the impossible to obtain (theoretical) performance increase gained by moving from PCIE2 X16 to PCIE3 X16 would make for very little improvement in task runtimes anyway, probably ~1%. Even on a GTX580 it would be no more than 5%. The benefit would however be seen in supporting a much faster GPU.

It never even crossed my mind that the CPU would need to be PCIE3 compatible! I presumed PCIE3 compatibility lay with the motherboard and GPU. So it looks like PCIE3 motherboards are being sold when there are no existing CPU's that fit that board to make it PCIE3 capable. Asus and Gigabyte are at this too, however there is hope if you have a PCIE3 SB board; there will be a 22nm LGA1155 CPU's that will be PCIE3 compatible. If the next generation of GPU is say 60% faster than a GTX580 then using one PCIE3 x16 slot could be ~8% faster than PCIE2 x16. AnandTech demonstrated that the compute capability of an HD7970 is 9% higher using PCIE3 than when using PCIE2.

Anyway PCIE3 is fully backward compatible so I lost nothing, and later this year I will have more options if I decide to upgrade my GPU, even if it means a new 22nm 1155 CPU too.

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AnandTech demonstrated that the compute capability of an HD7970 is 9% higher using PCIE3 than when using PCIE2.

That's only true for this specific code. It really varies on an app-to-app basis: you could only work within the GPU cache, like MW does, or stream huge amount of data between system memory and GPU or require frequent communication between the two. In the latter case a faster interface will help, but only then.

@Damaraland: building two value-computers for crunching with 2 GPUs each seems like a good idea to me. You avoid many hassles, can get away with smaller PSUs and I dare say a Celeron G530 would be enough to power 2 GPUs at GPU-Grid. You could always drop in an Ivy Bridge Quad later on. Just don't skimp on the GPUs, that's not worth it :)

MrS

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Scanning for our furry friends since Jan 2002

You could always drop in an Ivy Bridge Quad later on. Just don't skimp on the GPUs, that's not worth it :)

Hmmm very, very interesting...

Ivy Bridge to launch on April 8

Prices of Ivy Bridge desktop CPUs

When crunching at stock the voltage on my i7-2600 is 1.18 and my i7-2600K is 1.05V. The i7-2600K uses 65W crunching; 30W less than the TDP, or just under 70% of the TDP. If IB with it's 77W TDP performs similarly then it's likely to use around 54W when crunching. The clock of the top IB is 'disappointingly' the same as the SB, 3.5GHz, and there are no more cores, but if it performs as expected, around 15% better clock for clock, then that would be the equivalent of a SB at 4GHz and only using 54W.

In terms of performance per Watt that's about 38% better than SB and at the same price. Tick-tock!?! Yes, but - for a crunching system with a top GPU the power saving would probably be <5% of the entire systems draw. Suddenly that 15% CPU boost doesn't look that special, and nor should it, GPU's are where the heavy work is done. To me Intel doesn't want 1155 to do too well. Intel began with dual channel RAM, rather than triple and 5years after introducing a quad core CPU we are still stuck with 4 cores for desktops. Why not a 4GHz IB, or at least 3.8GHz (without turbo)? It would have been inside 95W. Even a 3GHz 6 core CPU would have been ~95W.

So for GPU crunching the only real benefit of IB on LGA1155 is just PCIE3 support, assuming you have a PCIE3 capable motherboard. Even then this would only noticeably benefit those who purchase a high end PCIE3 capable GPU.
Anyway IB is due on 8th Apr (2months), and NVidia will probably release their big Kepler's around that time.

I would not want to be buying a system for crunching right now; to many not so great options, but if you must there are still choices. Either get a cheap GPU such as a GTX470 or a good GPU like the GTX570. A good GPU will still be a good GPU in 3months and in 6 to 12months you would still get a reasonable return for a SB and a GTX570.

The system choices are:
Something AMD to keep the cost down, an i7-800 or i7-900 based system. All of these have reduced/no upgrades paths for CPU and no PCIE3 capabilities. A bit short sighted and heavy on the running costs, but possibly lighter on the up-front costs, especially with an AMD system.

A SB with a PCIE3 capable motherboard. OK if you will be happy to upgrade to IB and want to get a replacement GPU (or perhaps two, but no more) in the future.

Alternatively you could wait until next week and content yourself with a $285 LGA2011 Core i7 3820 for a year. This will allow you to upgrade/add a PCIE3 GPU whenever they turn up at a reasonable price, say six to nine months, and without having to upgrade the CPU. Should you want to upgrade the CPU then there are existing 3960X and 3930K 12thread 32nm processors, a potential 3980X, probably within the next 6months, and a 22nm IB will come along in the form of Ivy Bridge-E some time in the more distant future (Q4).

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In terms of performance per Watt that's about 38% better than SB and at the same price. Tick-tock!?! Yes, but - for a crunching system with a top GPU the power saving would probably be <5% of the entire systems draw. Suddenly that 15% CPU boost doesn't look that special, and nor should it, GPU's are where the heavy work is done. To me Intel doesn't want 1155 to do too well. Intel began with dual channel RAM, rather than triple and 5years after introducing a quad core CPU we are still stuck with 4 cores for desktops. Why not a 4GHz IB, or at least 3.8GHz (without turbo)? It would have been inside 95W. Even a 3GHz 6 core CPU would have been ~95W.

You've answered your question:

GPU's are where the heavy work is done.

Intel knows it too, that's why the second benefit of IB is its IGP, which is much better than SB's. But it's still not a match for Fermi, nor Kepler, nor the new AMD GCN architecture, so from the crunchers' point of view the only benefit that matters is its PCIe3 support.

Sure, for GPU-Grid the CPU performance doesn't matter. Any Quad would be too much ehre to serve 2 GPUs. However, in BOINC land we sometimes run non-GPU stuff on our CPUs, which is very IB would be an excellent choice.

i7 800: outdated and you don't save much by going for S1156 compared to S1155.
i7 900: even more outdated and 30 W higher idle power consumption of the system. Bad choice (in the context of this thread).

@SK: expect ~2% more CPU performance per clock from IB compared to SB. 15% would be massive, I doubt even Haswell will be able to pull this off (except using new instructions).

Regarding higher clocks: Intel doesn't think it's neccessary right now. And they're probably right about this..

Regarding more cores: Intel is happy to give these to you.. in a fancy socket 2011 dress with 4 memory channels. Going triple channel on the mainstream platform wouldn't have been cost effective.

MrS

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Scanning for our furry friends since Jan 2002

i7 800: outdated and you don't save much by going for S1156 compared to S1155.

You could save a lot if you could buy some used i7-8x0 series CPU. Also, the socket 1156 motherboards (even new ones) are cheaper. A cruncher MB does not require SATA3 or USB3.0, only PCIe3 matters, when the Kepler and the IB will arrive in april, so I would rather wait to buy anything until then.

i7 900: even more outdated and 30 W higher idle power consumption of the system. Bad choice (in the context of this thread).

Idle power of a cruncher PC? This argument made me LOL. :D

Regarding higher clocks: Intel doesn't think it's neccessary right now. And they're probably right about this..

Agreed. If someone needs the extra speed, one could buy either a K or X series CPU.

Idle power of a cruncher PC? This argument made me LOL. :D

Sorry, I was actually thinking something.. :p
If you meausre idle power, the (modern) CPU is basically out of the equation. What's drawing power then is first and foremost the mainboard chipset, followed by RAM, drives etc.

So if a platform (with CPUs with similar excellent power saving features) draws 30 W more at idle, the same holds true under load. Example for a 100 W CPU, and simplifying a little:

S1155: idle 40 W, + 100 W CPU -> 140 W
S1366: idle 70 W, + 100 W CPU -> 170 W

MrS

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Scanning for our furry friends since Jan 2002

The i7-800's can only support 8thread CPU's (plenty for most), whereas the i7-980 and similar are 32nm 12thread processors. So for those of us that crunch CPU projects,
140W/8=17.5 and 170/12=14.16 W/thread.
So if you want more threads it's 1366 or 2011. 1366 is cheaper but doesn't support PCIE3. 2011 is more expensive to purchase but cheaper to run and 'some' boards support PCIE3. Lets hope April's arrivals are PCIE3 competent.

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Just please remember that while we compute compute for cures, we also are contributing to disease via environmental degradation. I can understand using your normal computer to crunch in the off-time but its questionable whether buying multi-kilowatt machines specifically for this is worthwhile. Chances are much of your energy comes from non green sources, but even if it does, a lot of pollution goes into the manufacturing of computer parts don't forget.

I'm sure it's fine if only a limited few are doing this but I don't think it would be reasonable for everyone to have 1000 watt computers running 24/7. And please, if you compute in the summer (I don't), dont put it in an air conditioned area because that will effectively triple (I think is a reasonable approximation) your energy consumption to compensate for it. On the flip side you could use it as your heater in the winter, which would effectively mean you are running it for free if you normally need a lot of heat in the area you have it :]

Just please remember that while we compute compute for cures, we also are contributing to disease via environmental degradation.

This is a hypocritical reasoning.

I can understand using your normal computer to crunch in the off-time but its questionable whether buying multi-kilowatt machines specifically for this is worthwhile. Chances are much of your energy comes from non green sources, but even if it does, a lot of pollution goes into the manufacturing of computer parts don't forget.

It's all the same for the gaming computers, and they don't generate any scientific progress, just pollution (and amusement).
Oh, and don't forget the known and unknown multi-megawatt supercomputers, used for rendering movies, breaking codes, monitoring phone calls, simulating nuclear weapons etc.

I'm sure it's fine if only a limited few are doing this but I don't think it would be reasonable for everyone to have 1000 watt computers running 24/7. And please, if you compute in the summer (I don't), dont put it in an air conditioned area because that will effectively triple (I think is a reasonable approximation) your energy consumption to compensate for it.

Triple (200% more energy for cooling) is overestimation. The air conditioner is a heat pump, it consumes the fraction of the energy compared to the transmitted energy. 15-20% more energy for cooling is reasonable. The Sun heats the Earth's surface in the summer approximately 1.5-2kW per square meters, so an 1kW computer is not too much extra.

On the flip side you could use it as your heater in the winter, which would effectively mean you are running it for free if you normally need a lot of heat in the area you have it :]

This is a self-justification. It's not free, because electricity costs and pollutes double compared to regular heating methods. It's worth it, when the heating is a side effect of crunching.

Compute centers usually calculate with a 1:1 ratio between generated heat and power needed to cool it down. So I agree: running PCs "just for fun" with an AC is not the best idea in the world.. although I understand it's kind of normal in some southern US states.

Running in winter: in Europe and colder regions it's normal to use much more (money-)efficient heating than electricity. However, as far as I understand, it's rather normal in (maybe again southern?) US states to heat electricity. In this case it's a 1:1 exchange, so "basically free".

MrS

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Scanning for our furry friends since Jan 2002

Electric heat pumps are common in the southern US, where temperatures generally do not fall below freezing. Further north, natural gas is common (what I have in North Carolina), as well as standard heating oil. It's a mixed bag. Geothermal is available, but not widely used to date.

Been crunching a while and had 2 different systems fail due to heat so be careful if you try to cram too many hot things is a box.

Had a 6 core 1055t with 3x 9800GT cards crunching and the mother board caught on fire!

Had 2x ATI HD 5770 cards crunching and the hot one (the top one that had restricted air flow) gave up the ghost. Separate those cards if you want them to last.

Been crunching a while and had 2 different systems fail due to heat so be careful if you try to cram too many hot things is a box.

Had a 6 core 1055t with 3x 9800GT cards crunching and the mother board caught on fire!

Had 2x ATI HD 5770 cards crunching and the hot one (the top one that had restricted air flow) gave up the ghost. Separate those cards if you want them to last.

Or use something like this:
http://www.netstor.com.tw/_03/03_02.php?ODI=
There are several different sizes available.

Heat always reduces the life of electronic components.

Had 2x ATI HD 5770 cards crunching and the hot one (the top one that had restricted air flow) gave up the ghost. Separate those cards if you want them to last.

That's why I chose the MSI board I mentioned before. The two PCI are well spaced. Plenty space for air flow between 2x GTX 560.

Or use something like this:
http://www.netstor.com.tw/_03/03_02.php?ODI=
There are several different sizes available.

That looks cool, but how does it work? It looks like all the bandwidth goes to a single PCIe 1x slot??

Or use something like this:
http://www.netstor.com.tw/_03/03_02.php?ODI=
There are several different sizes available.

That looks cool, but how does it work? It looks like all the bandwidth goes to a single PCIe 1x slot??

I don't personally use one so can't answer that, but I am sure the company will.

I don't personally use one so can't answer that, but I am sure the company will.

There's a pdf with specs on the link

I'm having a little trouble with the math but assuming I'm reading the specs correctly that Turbo Box will be a bottleneck. It looks like the Turbo Box runs from a 4x link that must be shared between video cards. The stated top speed is 20Gb/s (note the lower case "b" indicating bits).