If you've got two ATI graphics cards and a crossfire-capable mobo and PSU, is there ever really a reason NOT to crossfire them?
For example, if you paired a 4890 with a 3850, would it actually slow things down instead of speeding them up?
Also, what about DirectX versions? If you pair a dx10-compatible card with one that only supports up to dx9, will this cause any problems, or will the dx9 card simply "shut off" during use with dx10 applications?
I ask because I have a 4870 and am considering purchasing a 4890 for crossfire. I know the 5000 series is due soon, though, which will be necessary for dx11 support if I understand correctly. So, if I go through with this purchase, I would like to be able to pair the 4890 with a later 5000-series card, so that I don't feel like I wasted money on this upgrade.