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