ATI HD2400 slow with native driver on 11.2

I have ATI HD2400 card and used normal Linux-drivers on 11.2 64 bit. I tryed the Catalyst 9.11 driver before but it does not compile correctly on 11.2, so I unloaded it and went back to standard driver.

I only notice things are slow: building the screen goes slow but is acceptable. One thing that is very irritating is scrolling in the browser (Firefox)…it takes ages to the page to stop again ad right point.

I wonder if there are any settings I can change to get a better performance. See my xorg.conf here:

Thanks in advance