https://bugs.freedesktop.org/show_bug.cgi?id=101387
--- Comment #15 from Alex Deucher alexdeucher@gmail.com --- (In reply to Carlo Caione from comment #14)
Fortunately it disappears after ~2 seconds when plymouth kicks in. My impression is that the visual corruption is triggered again when interpreting some atombios code, not really easy to debug.
Probably just intermediate garbage that happens to be visible while the memory controller or display hw is being reprogrammed.