I used to run X ok on a Thinkpad 600, probably in 2004. I was using XFree86, not Xorg. I would try making a config file and simplifying it. It may be that the server is trying to use interal/external at once, or something else complicated, and that triggers bugs that you could avoid.
(Not related to X, but man cbb and note the FIXUP lines. I dimly remember that the rbus_min_start is needed on 600E but not 600, and 600 needed FIXUPs.)
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