It could be fixed by increasing the default display clock: https://people.freedesktop.org/~cbrill/dri-log/index.php?channel=radeon&highlight_names=agd5f;grmat&date=2017-01-03 @Eike: you have a faulty monitor, please don't suggest people here to send theirs back because there certainly *is* a software issue. @Jonas: Did you try forcing the mclock to high? It doesn't require a higher core dpm state but should fix your problem.