DP 1.4 KVM Interference Issues

Level1 Store KVM Helpdesk
1

KVM Model:

1.4 Display Port KVM Switch - Dual Monitor - Two Computer

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

5-gigabit

Problem:

Monitors are turning off and on constantly.

Monitor specs: 1440p@240hz. Both monitors are the same brand and were purchased / installed at the same time.

Setup info: PC1 is connected directly to a desktop with a Nvidia 3070ti. PC2 is a thunderbolt 4 dock used with various laptops.

When I first got the KVM, the fix was to upgrade dp1.4 cables (the ones that came with the monitors wouldnt work with the kvm at all), put ferrite ring cores on all cables including usb, and turn the refresh rate down to 120hz on both machines (basically dp1.2 spec). Things have progressively gotten worse over time. Now my desktop (PC1) will flicker no matter what refresh rate the monitors are set to, while my thunderbolt dock (PC2) seems to be stable for now.

This is my 3rd KVM. I have only ever upgraded due to monitor spec changes, but this is the first time I have bought one that isn’t the cheapest rebrand on Amazon. This is by far the least stable experience I have had. Hopefully someone has some helpful tips.

Other Notes:

  • Monitors and KVM are connected to the same power strip.
  • I have tried 3 different brands of DP 1.4 cables, but have had most stability with UGreen cables. The ones that came with the monitor do not work with this setup at all.
  • Ferrite rings worked for about a day at 240hz, but had to bring everything back down to 120hz the next morning to mitigate flickering.
  • Shorter cables didn’t change anything.
  • I have tried isolating the cables as much as possible without any success.
  • The KVM is mounted to the bottom of my desk along with the power strip.
  • The power strip is grounded.
  • I have tried multiple thunderbolt and usb-c docks and they all have the same issue. I’m confident the dock is not the problem.
2

Hm, almost always cable/bandwidth-related as you noted.

Ugreen cables have been proven unreliable for the KVMs, unfortunately..

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I had a full week of non-stop PITA with UGreen cables (in my case, it also involved DP → HDMI converter). There was always an issue: displays turning off, “sand” in the picture in 4 lane mode, resyncs etc.
While lowering the scan rate of the KVM somewhat helped with not losing the display picture (and my mind) every 5-10 minutes or so, I still couldn’t, for example, have a stable 120HZ 144p HDR mode, it still crashed regularly.

What ultimately helped was to throw UGreen stuff into the bin (where it belongs, I am now convinced) and buy CableMatters cables. The moment I switched to them, all issues were gone.

This KVM is very sensitive to cable quality, and UGreen being just generally “meh” gets immediately apparent.

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Welp, guess it’s time to buy new cables. Thanks everyone!