Geez, did I not write this down? At least, I remember fixing Dave's PC but not how I did it. I'm sure I stuff it into tongfamily.com, but from the 6,000 plus posts I have, I can figure out how to find it.
But, basically, a few years ago, Dave's PC died. I thought it was the power supply, so he bought a new one. I can remember my confusion when I plugged it in and it just didn't work. The fans would power on, but it would not power up. He reminded me it had to do with something obscure having to do with startup up voltages and flipping a dip switch on the motherboard or power supply to make it work.
Now it's making me crazy because searches with google (and the handy site:tongfamily.com) pragma to only do a site search do not yield what I want. I have searched for PC and power supply and Dave and can't find it. That's because I mentioned Vlad but not Dave in my post.
I'm dimly remembering that maybe it had to do with using the wrong Motherboard power supply cables. Maybe it was the difference between PCIe cables and Motherboard power supply cables? There is a strange thing where they have the same connectors but they have different pinouts. There is for instance a 4-pin 12V cable that modern PCs need in addition to the 24-pin mainboard connector. And there is an 8-pin 12V version as well. As discussed in the post from April 2020 during the build.
And these have the same pinout as the PCI 8-pin cable but are not compatible and one are labeled PCI-E cables and the other is named CPU Cables, so beware