I recently bought another HD5870 and almost every single game I run, runs slower and choppy with crossfireX enabled.

I have so far gone with my Q6600 Quad-core at 3.2ghz is what's causing this with bottlenecking the cards and I wanted to see if anyone else could share some insight.

Both cards are the same model.
yes I have latest drivers and APP profiles.
all drivers are upto date
4gigs DDR3
Windows Vista Ultimate.
Asus P5E3 Deluxe
PC Power and Cooling S75QB 750W ATX12V / EPS12V SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Power Supply compatible with core i7


Every game runs better in single mode.