I just tried updating to EL Capitan on my Mac Mini, I believe it is a 2011 or 2012, the last time they offered the quad core i7. It downloaded and started the process of installing and I was working on another computer when I noticed the screen was black. Now it won't boot or get beyond the apple. It does not chime or anything. I get a Kernel error like 14.7 but it goes by so fast I am not sure. I have a time machine back up but I cannot figure out how to boot up so I can restore from a time machine back up. Any help would be appreciated