xorg-driver/xf86-video-ati-6.14.0: Worse performance since last update

[O. Hartmann]

Since the last update of Xorg stuff, including the 
xf86-video-ati-6.14.0, the video performance of all of our 
AMD/ATi-driven boxes went worse.
The bad performance also occur with the recommendations made in 
ports/UPDATING for driver "radeon". Without those recommendated adding 
of options even with a working xorg.conf file the performance stays worse.

Worse means: using vlc (also after recompilation after upgrades made!), 
videos are massively bumpy and can not be watched with vlc-screen fully 
expanded to 1900x1200 pixel with HD4830 graphics card - this worked 
perfectly before.

Moving windows around now looks like having chunks of video content 
floating around - as on unaccelerated/slow graphics boards.

What's wrong?