I have problems with every newer driver than the release driver (8.921.2-120119a-132101E-ATI). I encounter the following problems with the OpenCL-Application:
C2Q 9550 @ 3.4 GHz, Asus P5Q-E, 8GB, Win7 64 Bit, Boinc-Version 7.0.25
2 Gigabyte 7950 WF3 (not crossfired when using BOINC, second card has a dummy plug instead of a display)
- Some tasks are not ending or send to CPU instead.
Nothing will run on the CPU. After there is a problem from the driver the application will hang until killed though.
I´m not sure, if the task is send to CPU, but I saw a high CPU-utilization on this tasks. Normally I have an utilization of about 3 % in average, but on the mentioned tasks I saw utilizations of more than 60 %, until I manually kill the tasks.
You can find such a task here: http://milkyway.cs.rpi.edu/milkyway/result.php?resultid=190662270
Similar problems have been reported here by others. I have the same problems and have not been able to upgrade past the 8.92 drivers that came with the 7970 cards. The common point is multiple 7000 series cards, often with a headless card, mostly on Windows 7, A general summary:
8.92 - works fine
8.95 - all releases (up through most recent) frequent crashing, BSOD, and/or hanging video drivers.
8.96 - all versions run fine no crash/hang. but - headless GPU's clock is stuck at 500MHz and cannot be adjusted.
8.97 - (recent unofficial release) same as 8.96, runs OK, headless GPU clock still stuck at 500MHz.
You said you use a VGA plug for one GPU. It is possible that the 8.96/8.97 500MHz clock issue will not happen when using a plug, you might try one of the 8.96 drivers. They are often released on the popular gaming/over clocking sites.
Please post anything you find interesting.