Multi-GPU black screen issue...

Hello all,

System spec: Arch with KDE (not using Wayland) PSU - 1000w CPU - 3900x RAM - x4 32G = 128G GPU0 - 2080TI GPU1 - 4060 x3 monitors 1440p x1 monitor 4k

I'm running a multi-gpu setup (4060 and 2080TI). Both cards work in isolation - I've tried all monitors with them from cold boot. System recognises them, and I see both in nvidia-settings and nvtop.

Normally I'm running x3 1440p monitors off of the 2080TI, this works fine. I'm not stretching the display across the three. They share a virtual screen, but are treated as individual desktops.

There is a 4k monitor that I have, but when I plug it into my secondary 4060 GPU all four monitors go black. Unplugging returns back to my 3 1440p monitors plugged into my 2080TI.

I'm running nvidia-dkms and nvidia-settings for drivers. There's a bunch of RGB vomit in my rig, fans and the like... 9 of them with dual commander pros. I have two KVM switches on my monitors (both tested in isolation, behaviour from monitors is identical with or without them) - monitors get used for work. Macbook Pro is happy using a 1440p and the 4k via a KVM switch. Cables all tested and sound.

I've got a power draw plug meter on order, so I'll be checking to make sure I'm not exceeding my PSU's output, but aside from that I'm clueless now. Any ideas what is going wrong?

UPDATE: I managed to resolve my issue, came down to nvidia-settings doing janky stuff.

RESOLUTION:

• sudo rm /etc/X11/xorg.conf
• sudo nano /etc/default/grub -> add nvidia-drm.modeset=1 to GRUB_CMDLINE_LINUX_DEFAULT
• sudo grub-mkconfig -o /boot/grub/grub.cfg
• sudo reboot now
• Log back in...
• xrandr --setprovideroutputsource NVIDIA-G0 NVIDIA-0 && xrandr --auto

That did the trick! For persistence of monitor layouts, I then opened KDE's display config (right-click desktop) and moved the monitors about to desired positions. Saved. Rebooted. Sorted.