These take 4x Quadro FX6000, which is based on the GeForce 400 architecture.  So, basically it's 4x GTX480.  Which is crap for mining, really. 

Should be fine, I ran a HD6970, a HD5870 and a HD7770 all off an OCZ 500W.  Changed it as the leads were starting to melt.   Got a used Zalman 1000W off eBay, job done.

Video cards produce heat, so they can't cool anything. 

Z77 motherboard is an expensive way of doing it.  Plenty of cheaper AMD boards out there which take 4 GPUs no problem.  Stick in a cheap Athlon chip, job done.

Never found the need to, everything just worked straight off.   

I'm running a HD6970, HD7750, HD7770 and HD5870 all in one machine.  Windows 7 running 13.4 drivers.  Works fine.  Noisy and hot, but it works.

They're on an Asus SABERTOOTH 990FX board, and a FX8320 CPU.  Powered off a 1kW Zalman PSU.

I get 500kH/s LTC from my HD6970.  It's loud and hot, though.  I was getting similar from an old HD5870, but it seems to have crapped the bed - artifacting. 

This.

CCC always decides to mess with the fan settings, even when it's told not to it'll decide to start messing again.  It's a pain in the hole.

92C there's something wrong somewhere, either the heatsink is clogged with dust, the heatsink isn't mounted well on the chip, or your fan settings are wrong.

Even my horrendously overclocked HD6970 runs at 85C with only 65% fan speed.  If I could bear the noise of a 100% fan it'll run at less than 60C.

The old HD5870 I got ran up in the 90C area, turned out the previous owner had stripped off the factory TIM and put on some shitty silver stuff, it was like glitter mixed with butter.  Horrible stuff.  I replaced it with some ancient old white compound (this stuff came in a tube in the 80s and was for mounting heatsinks to TO-220 transistors to heatsinks).  Now it runs around 75C.

Depends on the mining software.  Reaper needs a shitload(tm), cgminer is fine with 2/4GB.  It does load the GPU's RAM more than BTC mining.
 

Started running this program, and it doesn't seem to want to mine for more than about an hour at a time.  The program still says it's mining, but doesn't actually send or receive any work to my proxy, or to the pool.

Nice idea, but I think I'll shuffle back to cgminer until it's fixed.

None of the above.  Don't bother, give the money to charity - you still get the same net result, but someone other than BFL benefits.

Well the ancient version of cgminer you're using probably isn't helping.  Try 3.1 which has 7970 fixes.

You're doing it wrong.

12.10 drivers work better for mining.

So the short version of this is:

The 7990 can mine no problems, but can't run Furmark.

Good thread, OP.   

I've got a HD7770.  Does about 200MH/s.  Doesn't overclock very well.  For the same price I bought a used HD6970 which does well over double the H/s.

As you've already got them, you might if you're lucky get 400MH/s out of the pair. 

90W per U?  Yeah, that's great for running the motherboard, what about the rest of the machine? 

My lowly 2xGPU machine (HD6970 & HD5870) is hitting close to 500W of power.  The heat it generates is ridiculous, too.  I have three GPUs running in a spare room.  It's a 12'x14' room.  Outside temp is a windy 4C today.  Windows are open.  Heating is off.  Rest of house is 18C.  Room with the mining machine in was 29C when I opened the door this morning.  It's now gone down to 25C after 4 hours.

IF you could build a 4U rack machine with 4xGPU in it, you're looking at 1600W of power, and giving out well over 1KW of heat.  Fill a 42U rack with those machines, that's 16KW of power, and 10KW of heat at a conservative estimate.  That's a lot of heat to shift.

I think you're sniffing glue if you think this idea has any legs.  The logistics are bad, the economics are worse.

Unless you mean renting out the rack space for servers for mining pools, then maybe you've got something.  But running miners is a silly plan.

No.  For mining, most GPU will run off a 1x slot, so if you don't mind using risers any old cheap board will do.

Facepalm. 

When it's fixed.  Slush has other concerns at the moment.  You'd know that, if you'd read the thread.