I work as a Computer Scientist at an academic image processing department. In my research, I regularly work with nvidia Cuda (http://www.nvidia.com/object/cuda_home.html) for high performance computing on the graphics card (GPGPU). These are general computations that have nothing to do with rendering 3D scenes. For GPGPU, SLI is not required. Therefore, it seems possible to me to put four 9800GX2 cards on a single motherboard, for example the MSI K9A2 Platinum V2 (http://global.msi.com.tw/index.php [...] incat_no=1) that has four (physical) PCI-Express X16 slots with double spacing between the slots.  
 
So far, I have tried to figure out if there will be any obvious problems with driver support. Since SLI will not be used, it seems that it can be done (see this thread http://www.tomshardware.co.uk/foru [...] cards-work and this one http://forums.nvidia.com/index.php?showtopic=62618 for more info.
 
Anyway, let's assume for now that it will work on the software side. So far, I am thinking of the following case and PSU:
 
case: Lian-Li Armorsuit PC-P80 (http://lian-li.com/v2/en/product/p [...] s_index=61).  
This is the only big tower case I could find that has more than 7 expansion slots. Using four 9800GX2 cards means that at least 8 slots are required. Any suggestions for alternatives?
 
PSU: Thermaltake Toughpower 1500W (http://www.thermaltake.com/product [...] /w0171.asp).  
This is the only PSU I could find that has four PCI-Express x8 connectors and four PCI-Express x6 connectors, which should be enough to power the four cards.  
 
I have no intention of overclocking (it seems like enough heat already)
I am trying to get a feeling of whether or not it will be possible to cool this case sufficiently. Any thoughts on whether or not air cooling would be sufficient?  

Just a guess but I'd think your going to need water cooling for the thing not to melt.  
 
You might start thinking about getting a dual power supply case, I've heard there is a cooler master stacker that has two psu mounting points. Also the Antec p190 comes with two power supplies.
 
Air cooling wise you might be able to leave the case open and stick a full size fan blowing across everything.

Thanks! Unfortunately, none of the dual PSU cases I've seen (include the Stacker 832 and the Antec P190) have the required 8 expansion slots...

Hi, I was just wondering, you must already have some sort of computer that you  use for day to day work? Because have you looked at the Tesla products from Nvidia?! This allows what you what to do, but some products are self contained in a separate case, thus eliminating the need for an uber MB and also it would eliminate the need for Uber cooling.
 
See this:http://www.nvidia.com/object/tesla [...] tions.html
 
The Tesla S870 GPU Computing System comes with 4 GPUs and 6GB of Ram.
 
just my 2 cents.

Unfortunately, the Tesla S870 costs $14000, and then you still have "only" 4 GPUs (instead of eight, with a <$5000) single PC. Part of the reason for doing it is also the "fun factor" actually  If you could cram 4 9800GX2 cards in a PC, the computation speed for suitable tasks would be +3TFlops, easily more than a 512-node supercomputer....

The ThermalTake Armor+ also has 10 expansion slots ( http://www.newegg.com/Product/Prod [...] 6811133056 ).  As far as PSU goes, I'm not sure another one is made with 8 PCIe connectors.  I heard something about a 2000W PSU at CeBit this year, but I don't remember any specifics.
 
If you scaled back to 3 9800GX2s you'd have a significantly lower cost, and less headache about actually powering and containing it.
 
I'd suggest filling your case with as many of these as will fit:
 
Scythe SY1225SL12SH 120mm "Slipstream" Case Fan 1900RPM
http://www.newegg.com/Product/Prod [...] 6835185060
or
Scythe DFS123812-2000 120mm Case Fan  
http://www.newegg.com/Product/Prod [...] 6835185053

This case would work great for cooling and even dual power. Your still limited to 7 expansion slots though...
 
http://www.mountainmods.com/computer-cases-c-21.html

Go for it man, 4 9800gx2 would be pretty cool to see, if u build this u gotta post pics so we can see, then maybe a little explanation of what you do so that  the rest of us understand why SLI was not important for gpgpu work.
 
Have as many large fans as u can, so that u have plenty of airflow, the more the better, as heat will be a huge problem, and watercooling might be too complex for all 8 gpu's...

 
I think I will eventually settle for three, but maybe after trying four for a short while We can use the cards in other PC's around the workplace too, so that should be no problem.
 
Thank you all for your comments so far!

Screw the case!  Just get some plywood and a drill :-D

plywood might be the duct tape computer building...

w/e u do post pictures when u have completed it with the 4 9800gx2's!!!!

I will certainly post pictures as soon as it's up and running, hopefully within a few weeks :-)

I am concerned that you will be able to find a power supply to support 4 of those. I dont know if they require any less power not in SLI mode but you can go here and see what is actually certified for your psu needs:
 
http://www.slizone.com/object/slizone_build_psu.html
 
This is specs for two of these cards, not four.  You may have to get out the plywood and mount two of these units to get the job done! (from a certified standpoint).
 
Good luck!

You will need 2x decent power supplies in a case that supports that, from what I see atleast.

More importantly...
Will it blend?
 
If u plan on putting these cards in other pc's after awhile, its kind of a waste having a mobo, psu, case etc that wont be needed.
 
Cooling shouldnt be a big issue TBO. Considering u have 4x dual card, single slot gfx cards, which are 2 cards in one yes? You then have 8 gpu's to cool. Doing this with water will be stupid really.
8gpu blocks a mile of hose, 2x pumps, 1-2 360cm rads... ur looking at ~1,000USD to do it properly.
 
Look at the design of the cards carefully, along with your case. You will need to make 4 seperate ducts, each with their own fresh air intake ducts. These can be made out of cardboard etc. Add a side fan plus one on top and bottom just to get the still air moving around a bit and you should be able to run the cards 24/7.

Ok several questions about this thread need answering, so I will start by asking the questions and making a couple of suggestions as well..
 
#1: What software on the market (or not) will actually utilize four graphics cards designed to be linked via sli( but wont be), and what will these graphics cards (which by the way are not designed for the task you are assigning them) be used for if not 3d acceleration or rendering?  
 
#2: Being a computer scientist Im sure you have done your research and realize by now that (4) 9800 GX2 graphics cards (giving you in your situation) a proposed 8 GPU's with which to do computations is a complete and utter waste of time because the software that runs these cards is not designed to have all four cards working as a team nor would four cards in the four PCI Express slots you are mentioning give you balanced throughput or data processing capability as the bandwidth provided by each slot will be different as 2 of those slots will be converted into 8X bandwidth instead 16x as the other two will be. Also the software you are using must be capable of using each card independently of the others as the four PCI Express slots will not report to any software that I know of as a team or grouping of (8) GPU's atleast not on a standard motherboard like the one you are talking about, without being linked in some fashion and again you have already stated that they will not be linked.
 
#3: For you to run (4) of these in tandem without failure for any length of time over say an hour or 2 would require a PSU far above the normal available wattage from your average reseller. You would need to frankenstein this build and have all non-PRIORITY devices: Examples include CD Drives and fans, on a seperate PSU. And have the primary system components on another  PSU:EX = the MOBO and VIDEO CARDS. Also hooking (4) of these up at all to have them all on a single PSU would require a PSU with a whole hell of alot PCI express Plugs and adpaters.. Atleast 8 PCI Express connectors will be required by the time it would be done. However with (2) PSU's and the correct timing when you flipped the switches on ..this wouldnt be a problem. IF you dont know how to do this research how to put (2) PSU's together in one computer, it is simply a matter of shorting certain pins on the motherboard connector cable, and flipping the switch.
 
#4: Also for the sake of mentioning it, you are forgetting that the amount of ram that the motherboard you are using is capable of supporting much lower than say your "super computer" or Tesla Products as was stated earlier. This will mean that your actual data throughput and processing power of the (8) GPU's would be severely hindered as a result.
 
#5: As Far as cooling goes this will not pose a serious threat to the operation of such a computer. The easiest and most cost effective solution would be to leave the case open on both sides ( kind of like a stripped down server rack
) and have a standard box or floor fan positioned blowing fresh air directly across the cards at all times. This will allow fresh air to shoot in one side of the  case and force hot air out the other side. Trust me this works amazingly well, as I have tested it several times during 12-16 hour gaming sessions with SLI'd graphics cards in the past.
 
#6: There are cases which will support your requirements for available slots , I would suggest looking at server class cases for this build which are typically designed for the high cooling capability and also expandability. If that fails you could always do a hack job to the back of a case using a Dremel tool.
 
Well thats my 2 cents.. I do not think this will work very well in execution, as the actual functionality of 4 of these together has not been tested if at all, and they were not designed for these sorts of operations. Also the power issue will be an "ISSUE". The Cooling can be solved with some effort on your part to withstand noise levels, but all in all theres a reason why the Tesla system costs 14,000. I think you will find out why.

@ thread title = YES

I just built a system using a Tagan case but it only has 7 expansion slots. It has plenty of air flow though.
 
http://www.newegg.com/Product/Prod [...] 6811294006