Hello everyone!
User Hakaitz🙂 of the Apple Support Communities has worked out a solution, that has helped me getting my old Mac performance back. It involves installing the graphics drivers from Snow Leopard in Lion.
This performance bug really annoyed me to no ends... Here's what user Hakaitz says in https://discussions.apple.com/thread/3198002?start=45&tstart=0:
There is a fix for this problem.
I just load with kext helper, the Snow Leopard Kexts from version 10.6.2 for the Radeon.
End of stutters on laggy animations on any version of lion. Works on 7.1 and 8.1 imacs (at least).
Here the fix:
http://www.megaupload.com/?d=11INQM1D
How to use ONLY RADEON 2600 USERS:
execute kext helper
drag and drop this files ONLY:
ATIFramebuffer.kext
ATISupport.kext
ATI2600Controller.kext
put your admin password and click on "easy install". I tooks a while to do the work. When finished, reboot (the kext helper aaaaalways hangs, its normal.
After that reboot your computer wont stutter anymore.
Hope it helps!