Dual-monitor 4X KVM: Long black screen pause (only on one machine) if switching too quickly

Hardware
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1

Hi,

I just recently got a new “1.4 Display Port KVM Switch - Dual Monitor - Four Computer” KVM. First attempt I naively used existing DP cables that I had laying around… despite being labeled DP 1.4, they were a mess. Tons of blanking and other issues, many intermittent. I then ordered a bunch of new 8K-rated, DP1.4 Club3D cables as recommended, and as short as possible (1-2 meters only). This worked much better.

So now I’m able to switch between my two primary machines. Both are modern Ryzen 5xxx systems with Radeon 6900 XTs in them. Both are running most of the same drivers. Win10 is identical between them.

Here’s the problem: Switching from machine #1 to #2 always works, semi-instantly. Going from #2 to #1 usually works fine if it’s been a while (at least a minute?). However, if I switch from #1 → #2, then #2 → #1 again within a few seconds (say if I want to quickly check something) then I am greeted with a black screen on both monitors for machine #1. This lasts for around 20-30 seconds, and then eventually the screens come back to life and everything is fine.

Going from #1 → #2 is never a problem. It’s only #2 → #1.

EDIT: it actually does happen going from #1 → #2 after all. Might be more tolerant of a quick switch in this situation (for unknown reasons), but it still happens.

Anyone know why this might be? Is it something going on with the KVM? Or a setting that is unique to #1 that I can possibly change?

2

Try to make sure refresh resolution sync polarity etc are the same between hosts.

Cru on windows might be needed.

3

Hi Wendell! Polarities for both monitors on both systems are +,- (for H,V). If this is the case, is there anything else CRU can do to mitigate this issue? Thanks!

4

I’m wondering if when you switch inputs and the monitor “disappears” that the handshake “hello are you there” thing is still happening when you switch back.

5

Yeah that’s what it feels like to me. Perhaps the system is polling for the monitor to check if it’s OK to put the graphics card in a low power state. And if I switch back during this time period it goes off into the weeds somehow, until it hits a timeout… at which point it recovers. Would be great if I could figure out what that setting is. :slight_smile:

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