I have 2 r9 290's but in watch dogs if I crossfire my frames drop really bad but if I use only 1 gpu they don't, this is the first game I've experienced this with, are some games just crappy for xfire?
amd fx 8320 @ 4.4ghz
asus sabertooth 990fx
power color pcs+ r9 290x2
in game settings are on high
Xfire - very hit and miss in terms of games that scale well. Should be sorted out in upcoming driver releases.... we hope.
edit# just thought Id SLI is no better.
Same thing happened with me in the AC games. Ubisoft makes shitty PC ports.
This was a very common problem when I ran crossfire. IIRC you can mess around with the crossfire profile in the CCC. I would say ~7/10 times I could get better performance by messing with the crossfire profile and setting it to AFR mode. You could also try messing with the game settings in Radeon Pro if that's still a thing.
These issues are why I left crossfire though. Sometimes there just wasn't anything that I could do to fix the problem.