Does this matter?

Okay i have 2 ATI Radeon 5770's in crossfire, but on CPU-Z when i look at my cards, it says card 1 has a 400MHz core clock but it says card 2 has a 399MHz core clock speed? I am running them in crossfire but im not sure ifit works properly since i thought to use crossfire both cards had to be indentical. Is this an error in CPU-Z or is my second card randomly 399MHz? Thanks.

Yeah, i wasn't worrying about performance or anything like that i was hust wondering if crossfire wouldn'y work since the 2 cards where not identical.