iMac rebooting issue

[donnation]

I have a 2011 27" iMac that I have never had any issues with. I upgraded to Yosimite without any problems and also recently to El Capitan without issue. When the most recent El Capitan firmware update was released I began the update process. For whatever reason, my iMac froze during the update process and it wouldn't complete. After about 10 hours of it just sitting there I shut the iMac off. When I rebooted it it stop loading on the greyish apple logo screen and just sat there.

I decided to restart it and hold down cmd-option-R. When I did this I clicked on reload OSX. It gave me the option of reloading it on to the HD, showing that everyting I had on it was still there. It reloaded fine and I didn't lose anything.

My problem is that I needed to do another reboot later and the system froze again on the Apple logo like it did the first time. I had to reload the OS again. Is there something screwed up here that could make me have to reload the OS every time I reboot the iMac. Thanks!

 

[Rob Phillips]

It sounds like a hardware compatibility issue with El Capitan. Have you done any upgrades to your iMac or are you still running all OEM hardware? Do you have any non-Apple peripherals connected? If so try disconnecting everything for a while and see if the issue persists.

Either way, I recommend contacting Apple Support, especially if you're still under warranty or you have AppleCare.