problem getting pseudocolor

[Neil Smith]

CentOS 5.3 on dual-boot Apple Aluminum iMac with ATI Radeon HD 2600 XT  
card.

If I specify in /etc/X11/xorg.conf a screen0 with depth 8, X11 can't  
start up, giving error of 'invalid depth = -1'.

First off, is this video capable of 8 bit pseudocolor in the X11  
shipped with CentOS 5.3 distro?

I don't know what the specs are for this monitor ... like horz and  
vert refresh ranges, if that even matters in this situation. Does  
anyone have an example xorg.conf, or the relevant sections, to get  
pseudocolor on an Alu iMac?

Thanks,
-Neil