https://bugs.freedesktop.org/show_bug.cgi?id=102646
--- Comment #62 from Alex Deucher alexdeucher@gmail.com --- (In reply to Scias from comment #60)
I also noticed it doesn't happen if using dual/multiple screens. Looks like the vram clock is forced to the highest state in this case. Is this a normal behavior?
Yes. Memory reclocking has to happen during the vblank period to avoid flickering. If the vblank period is too short or you have multiple monitors where the vblank periods are not aligned memory cannot be dynamically reclocked.