crossfire skip problems

[gordesky1]

im crossfireing a 4890 and a 4850 ya i know kinda a waste of the 4890 and the extra 512mb .... but it is a bit faster with the 4850 with it like 10 to 25fps more.

 

but there's a problem sometimes like maybe every 10sec there's a skip and it drops like 30fps

 

like on left 4 dead 2 im getting 160 to 170fps with crossfire before with just the 4890 i was getting 130s to 140 but every 10sec there's a slow down skip that drops the fps is it because im mixing the 2 cards or drivers or a tweak i have to do??

 

oh i also using windows 7 64bit

 

im just trying to squeeze little more out till the 5890 comes out:)