4 monitors but only 2 turn on

This is weird. I have 4 monitors and xrandr detects all of them but only 2 are showing anything, the other 2 are black-screen.

xrandr --listmonitors
Monitors: 4
0: +*HDMI-0 1920/598x1080/336+1920+0 HDMI-0
1: +DP-0 1920/597x1080/336+1920+1080 DP-0
2: +DP-2 1920/597x1080/336+0+1080 DP-2
3: +DP-5 1920/598x1080/336+0+0 DP-5

So, the top 2 monitors which one is HDMI and the other is DP show properly but the 2 monitors are not showing up.

However, if I unplug the DP for the 2 bottom monitors then they display perfectly fine. But this is very annoying after every reboot.

How to do i get all for monitors to refresh and display after every reboot, instead of just the top two?

EDIT: just for clarification I’m doing this on a desktop PC with an NVIDIA 4080 card that has 4 display outputs, 1x HDMI and 3x DisplayPorts. Also, this issue doesn’t happen in Windows.

You may just not have enough power for all 4 simultaneously from either the GPU or PSU.

I’ve got plenty in the tank in the gou department, NVIDIA 4080. Could this be an NVIDIA issue maybe?

My computer is a Dell Alienware AMD R15 (2023).

Unfortunately anything can be an nvidia issue.

How are you doing 4 monitors with the laptop - I tried with my Lenovo Legion thinking the same thing, and it was my docking station couldn’t handle more than 2 at a time even though it had 3 outputs.

I have a thinkdock usb-c 2

I’ve got 4 outputs at the back of my machine. I’m pretty sure they’re all coming out of the NVIDIA card. There’s 3 Display Ports and 1 HDMI.

Check your user manual. Just because you have 4 outputs doesn’t necessarily mean you can use all of them.

It doesn’t mean you can’t either, I’m just suggesting to verify it with documentation.

That was a problem I ran into.

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All 4 monitors work fine so long as I plug them in after I’ve booted up. Actually, KDE recognises them even if they’re already plugged in, but nothing is displayed on 2 of them. As I said, I have to unplug them then plug them back in and then and then everything is fine. This issue doesn’t happen when I boot into windows.

This sound like a bug in KDE. What happens if you change something inside the KDE Monitor settings?

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As an experiment I tried installing Fedora 39 with Gnome. It does the same thing! After booting up it only shows 2 monitors, even though gnome shows the other other 2 monitors as active in gnome display settings. Exactly the same as KDE.

This sounds like a hardware limitiation, just because it has the ports doen’t mean all can be used at once

And I tried Ubuntu 23.10 and it works fine. Huh? That’s weird. Maybe I’ll stick with Ubuntu but now I have an issue where my headset is being detected as only headphones with no microphone but that will be something for the Ubuntu forums I guess.

Anyway, why does the 4 monitors all work in Ubuntu without having to unplug and plug them all back in again?

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I’d be comparing the different program versions etc and trying to find out what is working different/ but stick to what works is always my fav solution

I’d look to see if Ubuntu is using an older Nvidia driver. It’s totally possible Nvidia updated the driver and it’s broken on newer distros. Nvidia has all sorts of things that happen to it on Linux. It’s a regular headache unfortunately.