imac 9400m lag lag lag

[braid]

Hello there!

I'm using a imac 20" with the 9400m. But I'm having issues with lags in expose. When I use the functions, all windows for instance, the animation is lag, BUT, when I keep doing it, over and over again, suddenly it gets smooth!!! I compare with another imac, with radeon here (an old edition) and there is no lag, even when you shoot the "all windows" command for the first time.

I suspect the gpu is under the normal frequency when idle, then when I do the all windows over and over the frequency is increased then the lag goes away.

What can I do for fix it? Overclock to the normal frequency the gpu? if yes, how can I do that?

10.5.8 here, tested with the snow too, same problems.

thanks