... until buy a Western Digital drive, open up your iMac and remember all that stuff you read two years ago about the thermal sensor cable. And then you find the stupid plug is completely different from that port on a Western Digital. So your only option is to find some replacement cable -- which I couldn't really find when I searched -- or to go back to the original 500GB drive down from 2TB. Then you get to figure out how you're going to restore your Time Machine backup when you have about 800GB of stuff on it. So in other words my iMac being on the fritz continues. Couldn't really restore everything I needed with the old hard drive in its 2013 state, so I reformatted and will pull off what I can from the Time Machine. This sucks. Don't ever buy another machine with an internal hard disk, folks -- not that Apple allows that any more!