I've built a mining rig running Ubuntu 11.10 with 3 Radeon 6850 GPUs.
When I run
./poclbm.py without any arguments, it returns the list of available devices as...
 Barts  Barts  Barts  AMD Sempron(tm) 145 Processor
giving me the (possibly erroneous) idea that I seem to have the drivers setup correctly.
When I start up one miner and pass the argument to use device 0, the hash rate is reported at slightly over 200 Mhash/sec. However, when I start up another pointed at device 1 in a separate term window, the hash rate for both is reported at around 100 Mhash/sec. And when I fire up the third miner and point it at device 2, then all three miners report their rate at around 60-70 Mhash/sec.
This suggests to me that the miners are not honoring the device argument that I'm passing and all dogpiling on one of the devices (probably the freckle faced red-headed one).
This happens with both m0mchil's poclbm and with PhoenixMiner. Below are the arugments I'm passing to each...
./poclbm.py http://username.worker:email@example.com:port -d 1 -v ./phoenix.py -u http://username.worker:firstname.lastname@example.org:port -k phatk2 DEVICE=2 VECTORS BFI_INT
Any ideas what I might be doing, or have done, wrong?