What happens when a cpu fails vs a gpu.?

If a computer fails, could you tell if the point of failure was either the cpu or the gpu? Could a failing cpu cause screen artifacting?
Update: Update: find my other question for the full story. The device im talking about isn't a pc, but rather a tablet. I charged the battery overnight and it
still won't turn on. Before it died the screen started to artifact.
6 answers 6