Quote from: mrb on June 14, 2011, 09:14:37 AM

hdminer's target market is not you the home user, but cluster owners who operate 20+ GPUs and are power or cooling constrained (eg. power circuits at 80% utilization per the US National Electric Code), yet need that +6.3% perf improvement without increasing power consumption or cooling needs.

I don't know what speeds they're getting at what temps but I'm able to do 2.43GH/s with 3 6990s at 1300w (10.83A) after 15 mins when the fans have been running at 100% for some time and temps are higher. Temps are all below 80C on air cooling on all cores except for a defective one that's always 12-20C higher than the other core on the same card (I limit the overclocking on that core so temps remain in the low 80s; perhaps I only need to reapply some thermal paste on it but I'm RMAing it to avoid any warranty issues). At times (probably when the AC kicks on), temps will be in the high 60s to low 70s. The thermostat is in another room and set to 76F in a very hot climate (currently over 100F outside) so it'll go on and off at various times. This is with an enclosed HAF 932 case with one 200mm fan removed and 5 120mm fans added.

What seems to makes a big difference is the PSU used. 10.83A on a 15A breaker (it's actually on a 20A breaker but I'm treating it as 15A for safety reasons) means I still have 1A to overclock it to possibly 2.50GH/s. I've also got plenty of room to add more cooling if necessary to bring the temps down. I'm comfortable with them running in the 70s and spiking into the low 80s for a short period of time. I've used a cheaper PSU and could only do 2.38GH/s while pulling over 1380w. I use two PSUs but only swapped out the main one. Mind you, the better main PSU isn't high end at all so if you're willing to pay a hefty premium, perhaps it'll be able to do better. The secondary PSU is on the cheaper side so that could be improved as well. The extra fans I'm using are cheap Yate Loons and not something expensive like the jet propelling Deltas that can pull in over 2x as much air flow. I don't even have a big external fan blowing on it.

I'm also running Linux, which means I'm more limited on the things I'm able to tweak (but with the custom tools I've made, I think I'm very close to what someone on Windows is able to do).

If your customers are getting the same rates or less than what I am with those constraints, they're spending a lot of money for things they can tweak on their own. At 1300w for 2.43GH, that's an efficiency of almost 1.87MH/J for the entire machine. When the time comes, I can make it go slower and be above 2.1MH/J (likely more) for the entire machine or above 2.4MH/J per card.

Also, assuming that hdminer is 6.3% faster, that'd mean they need to be doing at least 76.2GH/s to do better than spending the same amount of money on extra 6990s. I agree with Jack of Diamonds that you're pricing yourself out. If people do the proper research, they wouldn't be paying 250 BTC, let alone 100 BTC for something that is 1.2-2% faster. At 50 BTC and 2%, you'd want to do at least 49.7GH/s to do better than adding the same amount in extra hardware. I also suspect that it being faster means it will probably use a little more power, though not necessarily in the same proportion as the increase.