so you are running something like 915-950/150 under linux?
Yep, pretty much. Here is one new set of 6990's under burn-in, about 36 hours of data:
[ALL (30s):1686.7 (avg):1686.9 Mh/s] [Q:18011 A:41153 R:270 HW:0 E:228% U:22.95/m]
GPU 0: [418.6 / 419.4 Mh/s] [Q:3558 A:10141 R:58 HW:0 E:285% U:5.69/m]
GPU 1: [424.4 / 423.9 Mh/s] [Q:4674 A:10368 R:72 HW:0 E:222% U:5.81/m]
GPU 2: [420.1 / 419.6 Mh/s] [Q:3602 A:10050 R:71 HW:0 E:279% U:5.63/m]
GPU 3: [423.7 / 424.0 Mh/s] [Q:4639 A:10361 R:67 HW:0 E:223% U:5.81/m]
The cores are clocked at 935, 945, 935, and 945 respectively. So an average of 421Mhash/core I guess (the second number is the total average since it started up). Once put into "production" it will be in a cooler place with more airflow, so I'd expect clocks to go up 5-10mhz a core. These two cards are performing better than average so far, but nothing exceptional. Memory clocks are 150Mhz across the board.
Adapter 0 - AMD Radeon HD 6990
Sensor 0: Temperature - 78.50 C
Adapter 1 - AMD Radeon HD 6990
Sensor 0: Temperature - 74.50 C
Adapter 2 - AMD Radeon HD 6990
Sensor 0: Temperature - 80.00 C
Adapter 3 - AMD Radeon HD 6990
Sensor 0: Temperature - 75.50 C
No special cooling here - just running in a cool (68F ambient) basement, inside a large full ATX case. This is used for burn-in, then the cards are put in a caseless environment with far more airflow on them. I do run the fans @ 100% 24/7 - I have had good luck so far, but others report early fan death doing so. Either way, I expect to swap out fans every 9-12 months in these, but have yet to have to do so.
The kill-a-watt has held steady at 880w, using a 1000W Kingwin PSU. Prior to the memory underclocking, ramping up all GPU's at default clockspeed read 1090w before it crashed, so memory underclocking = will save you money on power, and PSU's! Do it!
These temps have held steady and are typical. When in production, this is also targeted at 85C per core, vs. the 80C/core during burn-in. Some cores simply underperform/run hot of course, especially some of the earlier run units. I have yet to see higher clocks than 955Mhz be stable, but I also don't spend a whole lot of time tuning this area.
There is lots of random old information/mis-information about these cards out there. Wanted to get some actual data put forth based on documented data.
Hope it helps someone!