My current system works off of 2 4870x2, In crossfire mode. The problem is each one of these cards has 2 gpu's and when I start c9 only 1gpu is used, which causes significant loss in performance. Also, the gpu that's being used stays at the idle clocks, which must be indicating that catalyst is not detecting an active 3D process.
-Moreover, I have tried programs like RadeonPro to force the crossfire but it fails to detect it as an active 3d application. This however, did work on other games like TERA that had no support for crossfire. Also, all my other games like crysis 2 fully work with my default crossfire settings.
-Note: Even when I disable crossfire and use a single HD 4870x2, only one gpu is utilized and it still remains at idle clocks.