FPS improvement with Crossfire vs single card

[xringx]

I will have the opportunity to upgrade my system. I am thinking of getting a MoBo that supports Crossfire and getting another HD3870.

What kind of FPS improvement can I expect? Is it game specific as to the improvement? Say like CS Source vs Crysis (dont play it yet) or a game sitting on my desk that I havent installed, Neverwinter Nights 2????

Will 2 HD3870's be chocked by my CPU?

Thanks for your input!

 

[aznstriker92]

No it won't be choked. Well you will get a improvement, the highest in titles like COD4, HL2.
Maybe at least 50% I will warn you, sli and crossfire sucks in crysis.