Aces, you may want to give this a look.
XFree86 3.3.3.1 Video Compatiblity List
The compatibility isn't so much with RedHat, it's with X Windows. Actually, I'm assuming that your problem is with X, since you didn't say so.
Okay, back to the point. You want to make sure it's compatible with X windows, not with RH. You'll find, though, by following the link, that it's not (yet.)
I'd check
www.xfree86.org for updates, though. They happen all the time.
Mike
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