I've just experienced a rather odd thing on my iMac (late 2013).
It's hard to explain, but it's like everything was overlaying each other, with elongated black triangles and while I could see everything, I couldn't do anything. I tried taking a screenshot, but it doesn't reflect what I actually saw. I couldn't restart and had to turn off via the power button at the back.
Does this mean my iMac is its way out? :o(
Hello, ellis_1983
If rebooting your Mac doesn’t fix things, see if the problem still happens in Safe mode (hold the shift key down at startup). It can take much longer to safe boot (10 min) so be patient.
How to use safe mode on your Mac - Apple Support
Safe mode disables loading third-party drivers, forces the OS to clear certain caches and logs and does other miscellaneous housekeeping. It's non-destructive to user data so is safe to do. Very often certain weird software behavior is corrected by simply logging in this way as a troubleshooting method. When you're in safe boot, the machine will not be at its best performance, especially with graphics, but that's expected.
Does the problem persist while in Safe mode?
Exit safe mode by restarting your Mac normally and re-evaluate the issue again.
Hello, ellis_1983
If rebooting your Mac doesn’t fix things, see if the problem still happens in Safe mode (hold the shift key down at startup). It can take much longer to safe boot (10 min) so be patient.
How to use safe mode on your Mac - Apple Support
Safe mode disables loading third-party drivers, forces the OS to clear certain caches and logs and does other miscellaneous housekeeping. It's non-destructive to user data so is safe to do. Very often certain weird software behavior is corrected by simply logging in this way as a troubleshooting method. When you're in safe boot, the machine will not be at its best performance, especially with graphics, but that's expected.
Does the problem persist while in Safe mode?
Exit safe mode by restarting your Mac normally and re-evaluate the issue again.
Screen display
