I have a mid-2011 iMac (iMaC 12,1) that has suddenly come into a overscan mode. Starting today, I cannot see the top and bottom of the screen or the left and right sides of the screen at the same time.
Thank you, jsmithepa. If I put it in movie mode, I don't know how I did it or how to undo it. In desperation, I shut down the iMac, unplugged the power cord for 30 seconds, plugged it back in and turned on the iMac. The overscan mode was gone. ecomayecomay