Well even though this isn't 68xx series related. I just ran some tests of the few games I currently have installed.
System Specs:
965 x4 BE @ 4ghz
8gb DDR3 1400Mhz 6 6-6-18
HD 5850's @ 825/1000
Win 7 x64
Catalyst 10.8 w/ 10.8a CrossFire Profile
Using 60 seconds Fraps when no bench avail.
All settings in their respective games are maxed out. 1920x1200 resolution
Dirt 2 Benchmark
Single card: 65.6 avg ~ 57.4 min
CrossFire: 107.5 avg ~ 90.6 min +41.9 fps avg.
BFBC2 [Multiplayer Map Laguana, 10 ping and all alone]
Single card: 60.1 fps
CrossFire: 90.2 fps +30.1 fps
Mafia II Benchmark [PhysX off]
Single card: 48.9 fps
CrossFire: 86.2 fps +37.3 fps
Left 4 Dead 2 [Dead Center/Hotel] Bench started at same time when player is controlled
Single card: 155 fps
CrossFire: 226 fps +71 fps
well erocker i know crossfire works on my system but in crysis i get maybe 5fps from the second card and worse minimum frame rates yet in any Unreal engine game i get close to 80% scaling maybes its because im still on 10.4a but newer drivers just give me even shitter performance
First and foremost Crysis sucks. Secondly I've seen better results from CrossFire with that game many, many times so it's probably something on your end.