On Mon, 17 Dec 2018 12:05:11 -0800, mike wrote:

Standard debugging procedu
Divide the system into two pieces.
Test each individually.
Divide busted part into two pieces.
Test each individually.
Divide busted part...you get the point.

Right, standard troubleshooting procedures, except in a case like this
you can't very well do that, so what I've tried to do is more of a
substitution approach. I've tried two different PSUs, two (identical)
motherboards, varying numbers of RAM modules in varying slots, two
different SATA HDDs, two different SATA cables, and two different
operating systems on two different media (USB and DVD, total of 4
combos). I don't have another CPU to drop in, but I'm hesitant to think
that's the issue, and I haven't tried a different optical drive,
keyboard, or mouse. I did try a PCIe graphics card to make sure it
wasn't somehow related to the onboard video, but that didn't help.

Does the drive boot in a different system?

I don't really expect it to, but I haven't tried. The only other system
available at the moment is an older AMD-based PC, so that's pretty
different from what I'm working on. Let me think about that.

Does a working drive boot in this system?
rinse/repeat...

I'll give it a try, thanks. I expect it to blue screen, but that assumes
that it gets farther into the boot process than what I have now, so it
could indicate something.

FWIW, there's a lot of settings in the BIOS/UEFI

True, but so far I'm not seeing anything on the ASRock forums about the
defaults being unbootable. Lots of people talking about OC, but I'm not
trying to do that. Thanks for the suggestions.