Question? I updated mac os on my mac pro 6.1 a week ago, it was fine for several days. One day I did some video editing, rendered off a video and later in the night shut down as normal. When I booted back up the next day, no signal from HDMI on my monitor.
Tried diff cables and even plugged in an old mac LED monitor via mini display port, with nothing. So either its a software/driver issue, but how am I supposed to even reformat a mac without seeing the screen? or the GPU has incidentally failed.
Answer: Base on what I know the Gpu cards on this models has some weakness and lately due to the age many started to go bad and fail, one sign of going bad is few second’s of pixelated display image when unit start up, and base on what your telling me I would assume the worse,
it’s possible that one of the two AMD Fire Pro Cards in your A1481 Mac, changing them is not that hard but they cost a lot,
here is a link where you can find different and fire pro graphic cards.
If you want to reformat, remove the ssd and install in a MacBook Pro/Air that is 2013 to 2015 model and reformat or reinstall an older osx in other device and put back in the Mac Pro ,
Also it worth trying before removing the ssd try booting up in safe mode, maybe that works so you have chance to format.
1.Power on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.
2.Release the key when you see the login screen.
3.Log in to macOS.