hey i read it somewhere that alt-tabbing out of the game or if the game due to some reason pauses n the user comes to desktop then going back in the game will let the CFx non-operational for the rest of that session of the game...... is it so???
Crossfire and SLI only function in full screen. Alt-tabbing in and out sometimes , Windows does not give the game full 'focus'. Sometimes the task bar is still at the bottom, or not.
Hitting Alt-enter usually snaps a game back in to full screen.
To the original question, in one driver version I noticed something weird happen during Heaven benchmark, after going in and out of full screen, the gpu usage was not correct.
I believe that was actually mentioned in a driver update as a fix.
I have been alt tabbing out of Crysis 2 all week with no troubles.