HDMI 2.1 4-PC KVM switch woes with a shiny new 4K/160Hz/HDR monitor

Level1 Store KVM Helpdesk
1

KVM Model:

HDMI 2.1 KVM w/EDID & Serial Control - Dual Monitor - Four Computer

USB Interface (5-gigabit or 10-gigbit):

10-gigabit, working fine

Background

Worked fine since I received it in May/June/July 2024 (can’t remember which month) in a setup with 2x1440p 60hz SDR monitors. Korean no-name IPS monitors I got, used, in 2016.

The reason I got the HDMI 2.1 model is so I can future proof when the monitor(s) eventually give up the ghost, which one did.

PCs

Using the KVM labels:
PC-1: Windows/Gaming, 3090 GPU, HDMI 2.1
PC-2: Linux, workstation, AMD 8700G CPU via the HDMI 2.1 (ish - 4k/60Hz) connector on the motherboard
PC-3: None
PC-4: Work MacBook HDMI port

The new monitor

My MSI MPG 274URDFW E16M arrived today
https://www.msi.com/Monitor/MPG-274URDFW-E16M/Specification

  • 4K 16:9, 160Hz, HDR, HDMI 2.1 (2 ports)
  • It also has “dual mode” 1080P at 360Hz, but it’s disabled on the monitor

Initial Non-KVM test

To start with, I tried 2 “8k rated” cables from Amazon directly hooked up to the monitor. 2meter/6ft. Both work fine 4K/160Hz/HDR.

I am not using the 2nd monitor during any of this testing

Problem

The goal was to use the same previously tested cables:

  • 1 from the PC → KVM input(1)
  • 1 from the KVM PC-1(1) → HDMI 2.1 of the monitor

Note: I am using a dedicated troubleshooting monitor on Windows so I can access the displays menu / Nvidia Control Panel.

Windows recognizes the monitor, and you can set 4K/160Hz/HDR, however nothing is displayed. I tried 1080P/60Hz/SDR, and still, nothing is displayed on the monitor.

While everything is still on, I directly connect the monitor using either of the cables, same GPU HDMI port, and the picture is live, with 4K/160Hz/HDR or 1080p/60Hz/SDR (depending on the last settings saved).

I have tried both ports 1 and 2 on the KVM with this single monitor (ensuring to match bot input/output), but the result is the same.

Other Notes:

I am currently getting by using HDMI1/HDMI2 directly on the monitor, but it’s cumbersome when I’m used to the KVM :frowning: . The KVM is currently used for USB/Input switching until we (hopefully) get to the bottom of this.

Edits: minor typos

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Did you train the EDID to the new monitor?

3

Thank you for the quick response!

I was not aware of this. Looking at the manual, I assume you are talking about this?
image

What procedure would be adequate here?
Just to note once again, Windows sees the new monitor correctly via KVM, and I’m allowed to set resolution, etc. Unfortunately, no display is visible with the KVM.

1 Like
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Yes!

If the EDID is trained to a different monitor, it makes sense you’re not see anything (it would only work if the new monitor supports the EDID profile of the old monitor.) You’re going to want to plug everything in as usual and into the new monitor. Try pressing and holding the button for the “auto copy” period. Basically, once it flashes yellow, let go.

5

Thank you. We have some progress @Level1_Amber :

In Windows when I extend the desktop, while using the KVM, I can drive the display up to 4K/120Hz/HDR(10-bit), while the display supports 4K/160Hz/HDR(10-bit).

Setting the display to anything above 120Hz while in “Extended View” does not work.

This setup is not tenable at the moment, because when I switch to “Second Display Only” I get “No Signal” on the monitor. I am assuming that Windows wants to set 160Hz (default/max) which does not work.

In Any case, PC-2 (being Linux) does not work either, I am assuming for the same reason (trying to go for the max refresh rate). No evidence to support this guess at the moment. I don’t have the ability to connect a second display to Linux for troubleshooting, unfortunately.

Any ideas on what we could try next? And before we start, are these KVM switches 40Gbit or 48Gbit? That would, at least, explain the 120Hz limitation.

6

I just remembered, Linux machine’s motherboard can only do 4K/60Hz/HDR:

image
image985×697 27.7 KB

So I guess it’s maybe bandwidth, but maybe something else

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@Level1_Amber I didn’t want to bump the thread during Thanksgiving. Do you have any other advice?

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Thank you for the bump :slight_smile:

Did you ever try different cables? These seemingly random no-name Amazon cables are sus. They can work independently, but working cable 1 + KVM + cable 2 is completely different unfortunately

9

So this could also be a display stream compression issue given you don’t have enough bandwidth to do above 4k/120 without it.

Anything in the monitor DSC related? If the monitor is doing something weird to enable DSC that might be the problem. Strictly speaking the KVMs do support DSC, but something odd is going on if that’s the cutoff.

Anything in the OSD about fast handshake or eco mode or power save? Disable all that if so. It may also be worth powercycling the monitor (i.e. unplug the power brick from the monitor for a minute or two) and retry.