That's not true. Maybe it's your experience, but not mine. With previous AMD drivers CrossFireX was not working for me, but with the last 12.1 or 12.2 preview drivers it is now working, even if the fps improvement is only about 20-30%. That is without a specific profile for the game from AMD. I'm not saying there's nothing to do in the game engine, but maybe the graphic drivers have something to do in this too.
What Profile are you guy using or are you using Raedon pro? I took get 14fps or worst with 2X 5870s. Still I'm not worried, this is still a beta. ISI will atleased stand by rfactor 2 long after its release.
I havent been using any profile and I'm not sure if crossfire is on or not. I leave the profiles at Optimized 1x1, both GPU are sharing equal load. If anyone does have a profile please share your details. After installing 12.4s I get my lowest FPS about 15 to 20 on a full grid but once the action spreads out it increases to 40 to 80fps depending on whats going on this is with Max everything and level 1 AA. I could kill the shadows, AA and drop to high and get decent grip FPS atleased, I just deal with it. Its still to early to complain honestly, if you can get the sim running even on 1 card with medium detail your doing good. Give em some more time they'll get it optimized.
