I'm using the latest afterburner beta (12) and just switched from a single HD5870 to 2x HD6850s in crossfire. After a lot of messing around with drivers (had to downgrade to 11.10 with 11.9 CAP4 to get BF3 to run stable) it's smooth, unless I try to record, then I get an insane reduction in framerates, MUCH lower fps than when I wasn't running in crossfire. I might be playing with 80-120fps, but when I record, it drops to 40-50. Compared to the single 5870, I would be getting 70-100fps normally and very similar when recording, I barely noticed a drop at all. Does the recording feature not support crossfire or something? Incidentally, when I disable crossfire and just run one 6850, I get the same FPS while recording as I do in crossfire.
What resolution when running CF and what resolution when running singel? If recording fullscreen 1080p then @60FPS there will be a ~50MB/s write to your harddrive which is a lot or if you compress it that might also slow things down, higher resolution = more data = lower FPS. Try recording 1/2 frame and avoid recording to the same HDD as other things use at the same time, lowering your resolution can also help.
Its vice versa, it is crossfire is unable (and will always be unable) to handle recording effectively. Welcome to the world of ncie world multi-GPU limitations, ULPS and so on http://forums.guru3d.com/showthread.php?p=4179743
Thank you, that's the answer I was looking for but was unable to find with the search feature Time to return some cards.