While researching some Hardy video problems, I can't believe I forgot about these details for G3's although I think it will also apply to any box running an ATI Rage 128:
(Sure wish this was a sticky!)
I was hunting around and saw that ATI Rage 128 cards hang on glx, among other things:
and then I remembered that wiki listed above.
So for anyone running ATI Rage 128 cards, the wiki will be extremely helpful. Unless you are running a G3 iMac, your resolutions may be a bit different.
A working xorg.conf can be seen here, filled in with a bit more user-added detail:
Hopefully by disabling the glx and dri modules, possibly adding -nosplash- to your kernel parameters at either the second stage boot prompt, and maybe having to tweak your horizontal and vertical resolutions, you'll have some nice video. it can be done!