OK, the new catalyst 12.6 configured as "aticonfig --set-pcs-u32=DDX,ShadowPrimary,1" indeed seems to perform better when trying to scroll http://www.phoronix.com in firefox using a mouse wheel. This was one of the worst nerve breaking experiences before, which even made me develop a habit dragging a scroll bar instead (during my previous short attempt using ati catalyst drivers). Maybe I should run some benchmarks to get the performance numbers
Nasenbaer: thanks for the hint! It's a band-aid, but probably can help to survive until opensource drivers get good OpenCL support.
It run on legacy driver 12.6 beta but I can't see the improvements ehehe