[CentOS] CentOS 7, ATI video, ex-X, still fighting

Still trying to get it running. Updated CentOS 7, ATI video card, trying
to use the radeon driver, and, using the previous kernel, X appears to
come up, but gdm fails; with the 514 kernel, X fails to start.

And here's a twist: I just rebooted, with radeon.modeset=1 on the kernel
line... and for no reason I know of, I get *six* logs, Xorg.[0-5].log.
Does this suggest anything to anyone? I can't imagine it's trying to start
X six times....

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