Differences in the logs between xf86-video-ati-6.14 and xf86-video-ati-7.0:
* With 6.14 and the ati GPU enabled, Xorg seems to detect the ati card (it loads intel_drv in line 91 and ati_drv in line 96) but doesn't try to initialize the ati card (it uses the intel card, as it should, and there are no more messages about radeon/ati after line 96, just intel).
* With 7.0 and the ati GPU enabled, Xorg loads intel_drv (91), ati_drv (96) and a new (?) radeon_drv (102). Now there are several messages mentioning radeon after the intel messages (lines 150- and 471-), and then it segfaults.
* With 7.0 and the ati GPU disabled before starting X, Xorg just loads intel_drv (88). No mention of radeon anywhere and no problems afterwards.
I could disable the amd gpu in a service before xdm starts, but that's not a solution, it's an ugly workaround. I'd rather find out why 6.14 worked fine and 7.0 doesn't.