Displayport adapter undetected if connected on boot, detected otherwise

Hi there. I have a SuperMicro server (using a X10DRi-T motherboard) with an Nvidia NVS 510 card. I have two VGA screens (yes, they need to be VGA), so I use two Black Box Mini DisplayPort-to-VGA adapters (these ones, exactly).

The problem I’m having is pretty weird. The adapters are detected only IF they’re plugged in AFTER the computer has been turned on. If the computer is off, I plug the adapters and then turn on the computer, nothing. There’s no BIOS image in any of the outputs, and if I ssh into my system the nvidia-xconfig --query-gpu-info command yields “0 display devices”. Obviously the X server fails to start because there are no screens available.

If I then unplug and re-plug the adapters, they’re recognized and work properly.

At first I thought it had something to do with the Xorg configuration, but that’s not the case because I cannot even see the BIOS. If the adapters are plugged in right after I turn on the computer, I can see the bios and all that.

I’ve tried with two different NVS 510 cards, so that’s not the problem. I have not flashed a new BIOS because I don’t know whether that would have anything to do. I’m more inclined to think there’s something at an electronic level, something regarding the Displayport protocol maybe?

Did you check if a real dp monitor works to rule out a problem with the vga converters?

Yep, today we tried with a monitor with DisplayPort and it works. I’m guessing it’s a problem with the adapters, but it’s clear that they’re not “broken” per se, more like they’re kind of incompatible?

It’s kind of odd that they’re initialized by bios in a way that they completely shut down afterwards so they’re not even detected anymore when the driver loads and X starts up. Are you using efi or csm boot? In case of efi, is it possible to enable csm in bios (just enable, not use)?

Yep, CSM has been enabled from the beginning.