On Mon, 17 Dec 2018 23:03:53 -0500, Charlie
wrote:

Have you tried raising the CPU voltage slightly? My ASRock Z270 Extreme
will reboot on startup if the CPU voltage is too low.
It's worth a try although I'm at a loss to understand how it would boot
from a DVD.

Well that was an interesting suggestion. The default setting for vcore
is Auto, which resulted in a vcore voltage of 0.971v. Google seems to
indicate that 1.35v is probably the upper ceiling for the Core i7-8700,
but values of 1.1v to 1.3v are usually selected in order to keep the
heat under control.

Taking somewhat of a chance, I set vcore to Fixed (versus Auto), then
entered a value of 1.1v.

The system booted without issues from the Linux DVD, but it has done
that before. I shut it down and reconnected the SATA HDD, leaving the
optical drive connected, and tried to boot from the HDD. It booted
perfectly! That's the first time it has been able to boot from the HDD.
Now I'm letting it run through some boring routine admin tasks, such as
creating system snapshots, making and suggesting a list of software
packages that could be updated, etc. It's been running from the HDD for
about 3 minutes now, and that's a huge leap forward. [Edit: It's been
running for over 30 minutes and still going. Amazing!]

What are you running for vcore? Also, Fixed or Ratio or ?

In a previous post, I remember saying that I trust the defaults. Grrr...