As gentoo user, I've tried on a 2.6.25-gentoo-r7 kernel to change the preemption model and the Hz.
My computer is a Intel Core Quad 9550 on an Intel P45 chipset. The video is ATI HD4870 1Gb and the driver is fglrx 9.3. Xorg-server 1.5.3.
When setting to full preemptible @ 1000 hz, the system starts and everything runs fine.
But, when I tried Voluntary preemption @ 300 hz, the system crashed on X startup, leaving a graphical screen almost black with some BIOS boot post messages displayed here and there (sorry for this messy description of the problem, but it's rather hard to describe a crash).
The computer was still working on console mode, accessible with CTRL+ALT+F1.
So, my question is simple : is there any issue with the preemption model / Hz setting with fglrx ?
Some other people on Nvidia doesn't seem to have such issues. But perhaps my crash doesn't come at all from those kernel preemption settings.