On a PC with an Atom N2600 processor and an integrated Poulsbo gpu, rotation
using xrandr causes the screen to go blank. It actually seems to
work, the system does not crash, just the screen goes blank, and when
setting it back to normal rotation, it comes back to display. Setting
rotation to inverted has no effect at all. The rotation produces some output in
Xorg.0.log:

[   220.740] (II) modesetting(0): Allocate new frame buffer 1024x768 stride
[   225.507] (II) modesetting(0): Allocate new frame buffer 768x1024 stride