After changing the motherboard for an identical one, I cannot boot with DisplayPort cable connected in a NVidia GTX960 GPU

Question

I had a 3 years old Asus TUF Gaming B550M-Plus with a AMD Ryzen 5 and a Nvidia GeForce GTX960 in a dual boot Windows 11 Pro / Ubuntu 22.04 with a dual monitor primary DisplayPort and secondary monitor HDMI.

It died after several weeks of almost no symptoms, except for a weary system clock that could not update during shutdown, hibernation or suspension. I thought that it was a clock battery problem, but I removed and tested, and it was full.

I boot with no other issues but, next morning, dead PC with no lights at all.

I did the usual investigation, all parts were OK, except the motherboard. So, I ordered and got the exact same motherboard, of course with a different revision and BIOS after 3 years, but side by side all components and boxes are identical.

I installed and it failed in POST because of video (light and beep pattern); the strange thing is that when I remove the DisplayPort cable it POST normally and I could enter UEFI, reactivate Windows, etc.

Every time that I connect the DisplayPort cable I cannot boot. And when I connect it after POST, I can use Windows normally with the original DP/HDMI two monitors, but restarting PC, the same error...

I installed the GTX960 and the same DisplayPort cable in the other PC, no errors at all, but it is an ASUS Prime B560.

Investigating things in my PC, I know that the last UEFI version that I updated the dead motherboard with was a 2021 version; this motherboard is from a slightly different revision and came with a 2022 UEFI version, that I already updated to last, dated October 2023.

Any directions?

It is working; but Ican only boot with the DP cable disconnected and connecting it seconds after...

I did some search and did not find an answer.

Answer 1

During the research stimulated by post this question, I stumbled over a forums.tomshardware thread.

I learned there that some GeForce cards' chipsets have an issue with DP ver. 1.3 or 1.4, and the problem is exactly like the described above...

The fix is to update the GeForce firmware with this tool.

I just did and reboot. For the first time, it passed POST and entered UEFI settings.

In my case, a specific combination of motherboard's revision, UEFI and GeForce firmware were the issue.

Edit after some days: There was an issue that I did not care before all this mess occurred; in what seem random to me, GeForce Experience several times failed to update the driver with no explanation besides ask me to restart PC, what I did several times; sometimes it got updated, but more times than that it failed. There was one occasion, at the first semester of 2023 in which the driver got reversed to one from 2021 (! probably windows update fixed the failure, but I did not noticed)) and weeks later, it got update to a new one. But as all things were working perfectly, and I don't use it for (new) games, if ain't broken don't fix...

Now, it update driver without a flinch; maybe this too is related to the old firmware... if it fails again I'll post here.