I stumbled upon this thread because I've got an 11.04 rig with a 5970, but I can't seem to get both cores working efficiently. When I start the first core, I can get just over 300 M/hash, but when I start the second one, the first one drops in half.
I've followed these instructions to disable crossfire, but now after I start the first device, I get this error after starting the second device:
Kernel error: Unusual behavior from OpenCL. Hardware problem?
I tried https://bitcointalk.org/index.php?topic=14340.20 these instructions for plugging and unplugging the monitor before starting each device, but I'm still only getting about 300 M/hash, which is obviously way low for a 5970.
Ideas?