If part of screen is displaying correctly, GPU should be fine?
I have fixed up a few MBP's (usually broken screens), and have a question.
If a MBP has a wonky screen in which part of the screen image is garbled and part is completely fine (i.e. you can see the OSX desktop), can you conclude with any certainty that the issue is the screen (or perhaps cable) and not the GPU/logic board?
In my experience when there is a GPU issue, the entire screen typically does not display correctly.
I understand the best way to confirm is to connect to an external display, but don't have this capability right now.
Is this a good question?