spoiler

I very limited as to what computer hardware I have access to in where I live (not the USA), but I managed to get my hands on a used HP Elitedesk 800 G3 SFF and waited months for an AMD FX 6400 Low Profile to arrive. Now I am having trouble with this card.

I know the reviews state that the card can’t take advantage of my x16 slot bandwidth, but I expected to be able to use it in that slot, as the x4 slot is right against the power supply, and the card doesn’t breathe well at all there, and thermal throttles.

However, when I slot the GPU in the x16 slot, the PC won’t POST. I find no settings in the fairly limited BIOS options that would prevent this, and a test Nvidia GT 720 works in the x16 slot just fine.

I’m out of ideas to get this to work. Legacy/UEFI Option ROM settings make none. The port is enabled in the section that toggles availability.

I thought this would be related to my M.2, but the 720 is a x16 lane card, and it works fine in the x16 slot, so now I’m just left scratching my head.

Anyone have experience with this issue? Most results I find on my search terms are for custom builds with more BIOS settings than a business-class HP Elitedesk. That said, my search-fu is not what it once was before my mental illness advanced, and now I can’t as easily assimilate information, so it’s possible I am missing something right in front of my face.

EDIT: After days of fiddling, I made this post and went back to troubleshooting. It just booted with no problems. Scratching my head, but something I did in passing was the trick. Now to make sure I save these exact settings!

EDIT2: It turns out it was always working, and it is just BIOS/UEFI screens that will not display. This kept me from installing my base OS at all until I moved the GPU to the x4 slot. Since I installed the OS with the GPU in the x4 slot, now it boots to the point where I enter my luks encryption key and I’m good, but it still won’t show the BIOS screens. Perhaps I need to enable the legacy Option ROM for video?