Yeah, mining places a *much* higher load on your GPU than any game will. You're quite literally using 100% of the card's processing power (assuming your intensity is north of 6 in cgminer). Benchmarking sites have taken to using bitcoin mining as their GPU torture test to see how loud/hot cards get under extreme conditions.

I'd start with stock core clock, drop your mem clock to 150 Mhz below core, and then lower the card's voltage in Trixx or Afterburner by 10 mV at a time until it crashes (make sure you're mining while decreasing the voltage). Then go about 10 mV higher and you've got your minimum voltage. Use GPU-Z to verify that the core and mem clocks really are what you think they are (e.g., setting the mem clock to 300 Mhz in Trixx doesn't work on 79xx cards, but Trixx won't tell you that; GPU-Z does).

Before screwing with the card's voltage, make sure Trixx isn't set to restore your clocks upon reboot. Otherwise you can get into a loop of endless rebooting :/

I run mine at 1030 mV (according to Trixx... GPU-Z says they're actually running around 0.95 V), 975 core, and 825 mem. That keeps the temps around 77 C in a non-air-conditioned room, and gives about 580 Mh/s per card.

Eraserhead, how are you running the memory at 350? All of the AMD drivers I've tried force me to keep it 150 Mhz less than the core clock--any less and GPU-Z says the memory goes back to running at stock speeds.

I have this same case and played around with all of those fan positions--personally, I had the best combination of temperature and noise with the stock front fans running at 100%, a 140mm rear exhaust fan running at 100%, and a 140mm side intake fan (lower slot) running at 50%.

That fan setup is doing two things. First, you have more intakes than exhausts, so you have slightly higher air pressure in the case than outside it; this should help keep warm air exhausted by the GPU from being sucked back into the case (that 400R has air vents *everywhere*). Second, most of the air is coming from the bottom front--where it's coldest--and moving up and over the GPUs, CPU, and then out the back. The side intake is just there to keep pockets of stale air from forming over the GPUs, though if you only have one card, maybe running it at 100% will help. With multiple GPUs, I found a high-speed side intake would help cool off one GPU at the expense of all the others, probably because it was disrupting the airflow from the front intakes.

Have you tried undervolting the card? I don't have a 7990, but I've got a dedicated miner running four 7970s and the only way to make that work at reasonable temperatures was to undervolt each card down to about 1030 mV (stock was somewhere around 1125 mV).

Power is exponentially related to voltage (P = V^2/R), so small reductions in voltage yield large decreases in power, which translates to large decreases in heat. Hope you get it down to a reasonable temperature!

(And you can see cgminer's view of a card's voltage by pressing the 'g' key. I only have 7950s and 7970s, and it reports inaccurate voltages with both; better to stick with GPU-Z.)

There's absolutely no need for a 1500 watt PSU to run three 7970s. Around 850 will work, but power supplies are a great example of getting what (watt?) you pay for. Just because a PSU draws 850 watts from the wall doesn't mean it converts all of that into usable DC electricity. A cheap one may only only work at 70% efficiency, which leaves you with ~595 watts; a better (read: more expensive) 850 watt PSU should work around 90% efficiency, and give you a clean 760 watts, which is plenty to power three 7970s.

I'm running four with a Corsair 1200AX, but you could get away with less. I'd recommend the Corsair AX860i; it's 860 watts and super efficient. Mine is powering two 7950s and never draws more than 415 watts... should be plenty of headroom for three 7970s, especially if you undervolt them a bit.

Also, be careful about heat. Two cards mining in a case with poor airflow gets dangerously hot. You'll want a couple of strong intake fans in the front of your case, a strong exhaust fan in the back, and a weak intake on the side to keep the air around the GPUs moving. I've also found stock blower-style GPUs fans to work better at keeping the hot air out of the case--custom two or three fan GPU coolers just move the hot air off of the first GPU and directly onto the second.

Unless you specifically want an nVidia card for games, just get a pair of AMD cards. My desktop has two 7950s normally running cgminer at an intensity of 8, but when I want to game, I drop one down to 1. It's still powerful enough to run Bioshock Infinite maxed out, and when I'm not gaming, the two cards combine for north of 1Gh/s.

It'll be a year come June. But I think the earlier comments about the value of BTC matching the difficulty are on the right track, just reversed; if network difficulty outpaces the value of BTC to the point where miners are spending more in electricity than they're earning, the most inefficient will likely shut off their hardware. So, if BFL delivers reasonably efficient miners, there's still hope of making some money back. It's not a secret who runs BFL. If they don't deliver *anything*, there'll be a huge class-action suite or massive refunds for everyone who pre-ordered... maybe both.

(And this totally ignores the speculation aspect--if someone is betting on BTC hitting $10,000+ soon, then they'll mine whatever dust they can.)

This happens to me once in a while too, but it always gets fixed within a few minutes. I think the system just displays zeros while it's computing your reward, instead of a message saying as much. Maybe the server was having some trouble and couldn't compute it for a while, hence the multiple zeros? Slush's pool is working fine for me right now.

BFL_Josh posted last night with a photo of a working Single, saying that they're expecting a big order of the boards to arrive next week. So, not really much different from what they've been saying for the past 6+ months...