For those of you with RS600 (Intel-based X1200/X1250 IGP systems), I’ve just pushed (untested) support for those chips. You’ll need xf86-video-ati from git (master branch), and drm from git (r6xx-r7xx-support branch). The RS600 GART setup is more like R6xx/R7xx chips than the older IGP chips, hence the drm code being on the r6xx-r7xx-support branch of the drm. I don’t have an RS600-based system, so this is untested and may need a bit more work. If you have such a system, please test and let me know how it goes.
UPDATE: I’ve gotten confirmation that this indeed works! I’ve pushed a mesa patch as well to enable 3D on rs600 chips and Dave has queued the drm patches. Also, to clarify, the RS600 pci ids are: 0×793F, 0×7941, 0×7942. If you have an X1200/X1250/X1270 IGP system with another pci id, they you have an RS690 which is already supported.