this post was submitted on 18 Feb 2025
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Hi all, using Pop!os on my main machine and have Windows on my work PC. I use a KVM switch to go between them.

This works pretty well for the most part but one thing that's annoying is when the KVM is set to the Windows PC, and I turn on my main PC, it will turn on, but it won't output to any monitor after I switch to it.

When the KVM is switched to the main PC before booting, it boots and displays to my 3 monitors without issue.

I assume this is due to my main PC trying to find an output and if it can't find one, just boot without, I just don't know how to change that behavior and searching online for documentation or similar issues hasn't gotten me any results unfortunately.

I'm using Wayland as well if that makes a difference. AMD 7700 XT GPU.

It seems this would be managed by systemd?I'm still learning the more in depth technical bits with Linux so please correct me if I'm wrong. I'm all about trying to learn.

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[–] [email protected] 12 points 3 days ago (1 children)

The problem is the kvm isn't emulating edid. It's a horrible problem that shouldn't exist. It makes most kvms useless. It's not mentioned in reviews that most kvms sold don't actually work.

Look for a kvm that supports edid emulation and does it with the resolution/refresh that you need ( for example DP 1.4)

[–] [email protected] 4 points 3 days ago

That makes sense, was thinking of buying a new KVM so that's likely the path I'll take.

Much appreciated.

[–] [email protected] 5 points 3 days ago (1 children)

Post specs on the KVM. I think to do what you're asking it to do it needs an EDID stand-in/passthrough to be able to explain the capabilities of the monitor and "hold" it's place when inactive instead of just sending info that's in standby or something.

I believe what's happening is the signal to the cable is cut off from the monitor, making your GPU think it's been unplugged, and there is no event to say "hey, I'm plugged back in".

Confirm a few things:

  1. Switch to Windows, wait maybe 15s, then switch back and see if the display is still working.
  2. Unplug and replug the display cable to the KVM after the display stops outputting and see if it comes back.
[–] [email protected] 3 points 3 days ago* (last edited 3 days ago)

Unfortunately its a no name KVM I bought used off eBay so no specs I can find, but I think you and Blue_Morpho hit the nail on the head.

I'm going to do some testing after work and see if I can maybe find specs, maybe a workaround if there is one. Was thinking of buying a new KVM anyways so if all else fails, I'll just shop around.

Thank you very much for your help.

[–] [email protected] 2 points 3 days ago

I’m assuming you use DisplayPort? Try using an HDMI output if possible.