The XFree86 4.0.x as shipped with RH 7.0 dies if I try to set the display color depth to 16 bits on intel 810 based motherboards. 24/32 bit color depth works fine though. Another thing is the "startx -- -bpp 24" that I used to use to set the color depth doesn't seem to work anymore. I had to select *only* 24 bit color depth modes in Xconfigurator for the 24 bit color to work. THe command line option didn't work.
I'm pretty sure this glitch is fixed in the current rawhide. Can you check it out, and let me know?
The -bpp commandline option does not exist anymore. -depth and -fbbpp replace it. You want the -depth one. Valid depths are 8,15,16,24. The i810 issue is fixed in Rawhide 4.0.3-15. ftp://people.redhat.com/mharris/testing/XFree86/