Cheaper build another pc box.
50 dollar mobo
100 dollar cpu
20 dollar case
60 dollar psu
40 dollar RAM
Lets say another 100 dollars for fidly bits.

If you are careful, you can stick two vid cards in there. One powerful vid card, one less powerful (the kind that gets power from the slot and does not need external power).

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I don't have a high-end rig, but on my old HP xw9400 I have 2 x16(x16) slots and 2 x16(x8) slots. I've only got room to mount 2 cards directly on the board in the x16(x16) slots (currently a GTX660 and a GTX650), but I had room to slide x16 riser cables into the 2 x16(x8) slots. That allowed me to add a couple of GT640 cards (which don't need any additional power connectors). I've routed the ribbon cables out the back, so the GT640s actually reside outside the case. They seem to run quite fine there. Depending on the length you need, the riser cables only run about 5 to 10 bucks.

I was looking at those cables *recently*. I just can't determine how to mount the card(s). Most mid-range cards don't mind running from a PCIe 1x slot...much. The only idea I could come up with was to mount the cards in a stripped out small case located right next to the main case. I'm still thinking about it.

My GT640s are just out in the fresh air.



The upper one is on a 6" cable and actually is hooked into a small slot in the back of the case. The lower one is on a 10" cable that allows it to rest on a plastic "egg crate base" that's suspended about 16" above the floor.

Cheaper build another pc box.
50 dollar mobo
100 dollar cpu
20 dollar case
60 dollar psu
40 dollar RAM
Lets say another 100 dollars for fidly bits.

If you are careful, you can stick two vid cards in there. One powerful vid card, one less powerful (the kind that gets power from the slot and does not need external power).

Even cheaper.

Dumpster dive an old but running Core 2 duo. It's not going to be a high power CPU, but it will have the grunt to feed a GPU pretty well. Fit a better PSU (600w) for ~ $60 and cram your spare GPU in there. Extra case fan if needed, but with only one card in there you won't need extreme cooling.

I can see the point of one of those boxes if you HAD to have the max computing power in one system. But we are doing DISTRIBUTED computing. If you have 3 GPUs you will arguably get better performance by mounting them in 3 PCs, with 3 CPU's to feed them. Run the PCs headless and administer them remotely with VNC, they wont take up any more space, use any more power, make any more noise etc. They don't even have to sit local to your main PC.

Jeff's solution, while not "neat and tidy" certainly makes sense if you are running out of space and don't have the space for yet another PC case - must try it myself - maybe a simple skeleton case just to keep thing together.

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Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?