For Fallout 3 I had to replace the atimugdpl.dll library with a 64 bit version I D/L ed from mydll.com in order to get it run right ( Poor performance, HDR flicker, water reflections all green )
As soon as I did that ...problems solved...like buttah.
And in answer to your question.... Yes ...performance is lousy for Crossfire.
I have to play at 2 AA ! In order to keep fps at 60...2 AA ! Unbelievable ! 4 AA works good for the most part but there are a few places where I get a 10 to 15 fps loss. And I like 60 more...
And I had to do the 9dx.dll tweak...!
I'm thinking of replacing the atimugdpl.dll library's again .
Also have to force AA and AF in CCC and disable in game AA and AF.
This game is lousy performance wise. My rig should be playing 2 versions at once.
I have a 5970 ( which is a Crossfire card )
19x12
2AA ( sometimes 4 )
16 AF
Ultra settings
V-sync on
HDR
Can't wait for a patch or a profile...still might replace the atimugdpl.dll libraries with the ones from Fallout 3. I can play Fallout 3 at 8 AA ...2 is an insult to me and my machine.
Begone evil software !