Chosen Solution
My iMac is showing vertical bars upon startup. It is a Graphics Card problem which is expensive to solve for a 10 year old machine, so I have decided to purchase a new PC instead and was wondering if I can use the iMac as an external monitor using Target Display mode. My question is, Does Target Display mode need a fully functioning GPU on the iMac, since it is essentially being used as a display using input from another PC?
Are you sure your GPU is gone? What happens when you plug in an external monitor? If the external does not show them then you’ve proven the issue is within the internal display. Post a few pictures from your iPhone so we can see the issue Adding images to an existing question Update (10/09/2019) Ouch! Your GPU’s Video RAM is bad. It could be just a bad solder joint on one of the chips. Using some flux and a good iron or better yet a hot air rework station you might be able to get it working again.
