Hey there,

I haven't had any luck yet myself getting my fairly capable rig equipped with a Voodoo5 PCI 5500 to do Quake 4. I haven't tried the latest Amigamerlin Drivers however, nor have I really taken a close look at the Sage OpenGL drivers (which are supposed to improve compatibility with newer OpenGL-based titles). So I'd start by making sure you have the absolutely newest drivers possible.

If it's any help, here's the system I've been trying to get it to run on (unsuccessful so far)