What os are you trying to boot? Are you using EFI? or legacy bios? It's
been a bit since I tried legacy bios, I know some new boards balk about
that.
Not sure if this is what you are running into, but some time ago I ran
into something where I was trying to boot an os that had been installed
as legacy bios boot. I got two different motherboards for that project,
I think the one was an Asrock and I don't quite remember the other but I
know I frequently choose Gigabyte. Intel CPU that time. Something like
610 or 620 chipset.
I had to enable CSM (compatibility support module) or it would not allow
me to boot the legacy os (could not find a bootable disk). And CSM was
not available in the firmware settings unless I had a graphics card in
the only PCI slot. But the customer's case didn't have room for a
graphics card. I ended up using an older model board which I had in
stock, that did not have that problem.
