Comment 48 for bug 129380

I discovered that the tiling option of the driver mostly solves it for me (Intel 945GM). I used "x11perf -scroll10" to measure the performance:

Normal screen orientation:
> 3000000 reps @ 0.0022 msec (465000.0/sec): Scroll 10x10 pixels

Without the tiling option, in "right" orientation:
> 800000 reps @ 0.0068 msec (148000.0/sec): Scroll 10x10 pixels

After adding Option "Tiling" "false" to the device section in xorg.conf:
> 2000000 reps @ 0.0026 msec (387000.0/sec): Scroll 10x10 pixels

Still a bit slower than in normal orientation, but I don't feel the difference anymore.