https://bugs.freedesktop.org/show_bug.cgi?id=76490
--- Comment #112 from Daniel Exner dex+fdobugzilla@dragonslave.de --- If I read that correct R9 270X is a GCN 1.0 card and thus should be supported by experimental drm-next-4.8-wip-si branch.
Is it worth trying? AMDGPU is using a yet another PM system (PowerPlay) , so perhaps it works better, without having to blacklist?