Hey, I have a 4870x2 (and another 4870 for trifire) but from what I understand with your post, you have just one 4850x2?? The Crossfire is always on. From what I understand in order to disable Xfire on a X2 card you have to go in, and under AI, in the CCC disable Catalyst A.I. So when you have Crossfire disabled or enabled, it's essentially the same thing, and wont' change anything, try to disable Catalyst A.I. and you should see a drop in performance. Hope this helps