DAMN boy ... Holy BIIIIIP ... now we need to see someone with 7x Devil 13 7970x2 (or 7990) or likewise 7x 690 - to beat your upcoming system - (all of them watercooled of course) although for folding capacity, it looks like the openCL compute on the 7970 is best (until GK110)
Some of the bitcoin miner guys do that using external racks and PCI-E extenders. Unfortunately however more than eight GPUs in a single system image basically does not work in Windows, and even in Linux it's a configuration nightmare and performance drops off sharply due to driver limitations. The second GPU on the Radeon 5970 and 6990 are in fact paperweights for GPGPU apps due to being locked into crossfire mode (disabling OpenCL) and I'm not convinced AMD will fix that for the 7990 (they consistently lied about fixing it in the 5970/6990 in 'the next release' for the last two years).
The objective of this system is to achieve the absolute maximum possible single-system performance in certain OpenCL apps which use double precision (ruling out 680 GTX instantly with the utterly worthless 1/24th of the SP rate) and moderate amounts of inter GPU communicccation. I originally specced four 7970s + two 7990s, getting up to the 8 GPU Windows driver limit and leaving one slot free for a twin 10-Gig Ethernet NIC, which would have worked very well with the 8x 8x 16x 8x 8x 16x 8x PCI-E setup on the Asus board. However the 7990 was repeatedly delayed, and I need this system right now; I don't have time to wait around for guys to test the 7990 for OpenCL capability and for a 7990 single slot waterblock to come out. So 7 x Radeon 7970 at 1300 MHz ish it is.
Btw, CodePhoenix, how are you changing the 7970's to actually only take up 1 slot, as the waterblock itself will do most of that work in and of itself, but the Connectors usually take up two slots - how do you intend to modify them, or is there some special / standard way to do that ?
I am using AquaComputer blocks which fit into one slot (just barely) as long as you don't use backplates - I considered using 6 GB cards (e.g. Sapphire Toxic) actually, but I wasn't sure if they'd be clearance for the memory chips on the reverse side. For the brackets I ordered seven of these
from EK, since AquaComputer don't seem to have them for the 7970 yet. I also put some extra support rails into the case to hold up all the solid copper.
The most exotic component I'm using in this build is not electronic at all; it's the AquaComputer TwinConnect MAX-7
; I am not aware of any other off-the-shelf solution for cooling 7 GPUs at single slot spacing. Standard usage is to screw blockers down into the channels to configure it for series operation and blank off the unused slots, but for this build I am going to use seven slots and all four ports to feed it from the top and the bottom simultaneously (running 7 GPU blocks in parallel). Essentially I am going to run dual loops each with a resevoir Liang D5, CPU block and twin parallel triple 120mm rads, with one connected to the top in/out ports of the MAX-7 and the other connected to the bottom in/out ports (connecting the loops in the middle of the manifold).
I am not 100% certain this will work, but I'll let you know. :)