Startup Issue

[Desmond2Too]

When an imac starts up, displays the apple logo, then briefly displays a string of panic text (see screen shot) before reverting back to repeat the process, what could the problem be?

 

[TonyAguila]

When an imac starts up, displays the apple logo, then briefly displays a string of panic text (see screen shot) before reverting back to repeat the process, what could the problem be?

It probably points to the need to reinstall macOS. If you cannot even get into a normal boot stage, try rebooting in Safe Mode. It that too fails, try Recovery Mode. Power up and immediately hold down Command-R, or in the case of silicon Mac, press the power button and hold it until you get to the Options screen. (You need to give a hint of what model Mac you are dealing with.)

 

[Desmond2Too]

Thanks for responding @TonyAguila. It's a mid-2011 27" model A1312. After already trying the various restart methods (as you've noted), I disassembled the iMac components to remove dust & tried baking the GPU & reapplied thermal nano-paste before putting it all back together. Same problem on start though. Maybe the GPU is deceased but that doesn't make sense as surely the startup wouldn't display anything if it were. I have a pic of the panic report that appears briefly on the screen but the image is too large to upload here.

 

[TonyAguila]

Thanks for responding @TonyAguila. It's a mid-2011 27" model A1312. After already trying the various restart methods (as you've noted), I disassembled the iMac components to remove dust & tried baking the GPU & reapplied thermal nano-paste before putting it all back together. Same problem on start though. Maybe the GPU is deceased but that doesn't make sense as surely the startup wouldn't display anything if it were. I have a pic of the panic report that appears briefly on the screen but the image is too large to upload here.

Try performing a hardware test. Power up and immediately press and hold the D key. If the hardware test interface comes up, it means that at least your basic processes are still working. If it does come up with results, try and get the details and post it here.

I’m assuming that, at this point, you have already tried resetting the SMC and zapping the Parameter RAM.