Sorry for reviving this thread, but I have a little more info on what could be the culprit.

I had the same issue with my D865PERL board. No post, CPU stuck in reset. Turns out the CPU was unsupported. But even after placing in an celeron 2.6gHz, there wasn't any POST code execution going on.

Then I got an great idea to apply pressure on the ADP3168 buck converter chip. I powered it on when applying pressure and.... it worked!
...for a while that is. Then high side MOSFET started burning up.

Now I have replaced all the MOSFET drivers and the bad MOSFETs, but still, no Vcore whatsoever and no POST codes (due to missing Vcore).

Maybe this info will give somebody an idea of what's wrong here...

Karbist wrote on 2023-05-22, 07:27:

I suggest measuring the 3 power rails generated by the board, 2.6v memory rail generated by the mosfets near the ram slots 1.5v […]
Show full quote

I suggest measuring the 3 power rails generated by the board,
2.6v memory rail generated by the mosfets near the ram slots
1.5v rail generated by the mosfets near the agp slot.
and cpu vcore.
also board has a switching buck converter on the 2.6v memory rail, so make sure all the caps on that area are good.

Hi. My D865PERL seems to have 1.5V dropping slowly, according to the hardware monitoring chip. The lowest I have seen it so far is 1.328 V. I suspect I am experiencing crashes due to this, because it becomes lower when there is load on USB, SATA or PCI. Could you give me any advice?