Originally Posted By: artie505
Sorry to engage in the obvious again, but have you tried Resetting your Mac's PRAM and NVRAM, the repository of your selected startup disk?


Yes. Multiple times without noticeable improvement. Thanks for the suggestions. There may yet be something I have overlooked, but I'm beginning to doubt that. I just started up after having the machine off for four hours. It started right up. Sheesh! This seemingly irregular behavior is a pain.


Mac Pro dual Quad-Core Intel Xeons Early 2008; 16GB RAM; MacOS X 10.11.6, iOS 9.3.5