Up until recently I was working with 2 9800GTXs in non-SLI to bitcoin. They yielded around 37 Mhash/s each, so I decided to put in an ATI 6870. I have a 1k PSU and all hardware is a go, but I'm still having software/driver issues. I installed the ATI driver first (and now use the 6870 as my primary card) then installed the Nvidia drivers. Windows 7 (64) recognizes all three cards. I also put two dummy plugs on each 9800 GTX. Catalyst control and AfterBurner both recognize the three cards. My question comes in here. I am running GUIMiner (OpenCL) with each instance tagged GPU0, GPU1, GPU2 for each tab and I select Device [0-0] Barts, [0-1] Barts, [0-2] Barts for each respectively. However, whenever I try to run all three instances, the Mhash/s simply are spread out between the 6870 (i.e. each tab produces around 90 Mhash/s). Afterburner indicates that both 9800GTXs are at 0% usage, obviously. I'm looking for around 260-300 on GPU 0, and 35-37 on the other two. I'm assuming GUIMiner defaults to the primary display adapter, but how can I make these work in parallel? (I do realize it's tricky to mix cards like this). Any help is much appreciated and if someone can get me up to speed fully, I'd be more than happy to make a donation.