Im running 2 6870's in cf. I have an i5 2500k, MSI p67a mobo, 16gb 1600mhz corsair vengence ram, w/ 1300w lightning psu and 1tb samsung hdd. When I was home for break on both my laptop and desktop I was running at about 50 fps for the laptop and 100fps on the desktop. When I came back to school my fps dropped quite a bit. From 50's to 30's and from 100 to 30's on my desktop. I tried updating all the drivers and still have low fps.
i had to take it to a computer specialist but they have done very good work for me and i don't think they tampered with anything...the computer recognizes cf so im not sure exactly what the problem could be.