Displayport/KVM Blues

Greetings folks
I have been building PC’s for a few decades now and finally feel have a nice little setup with one PITA issue. I have been diving into forums and research for a month now and am at my wits end to find an answer (or at least an answer i am happy with). As the title suggest i am having issues finding a decent KVM for my DisplayPort setup.

I currently have a 3 to 4 system setup with a 6 +1 monitor setup. I have tried several KVM’s and will probably get the Level1 KVM to test when they become available in a couple weeks. The main issue i am having is that often my other systems will not display properly or at all when switching between them. It disconnects the monitors and then sits in the “entering power saver” mode. I have swapped cables and systems on ports to narrow it down, but seem to be chasing my tale. System A works on one KVM but not another. System B will work for a minute but then will either disconnect or wont reconnect when switching back. I Just got in a new batch of cables to try that and see what happens. From what i am finding is that the disconnecting is just a normal and unavoidable thing with displayport. Besides the disconnect i also have the rearranging of windows that is a PITA to rearrange when dealing with 6 monitors.

Help Me Level 1, your my last hope.

System A
Motherboard: Asrock X79 Extreme9
CPU: 4930K
GPU: Radeon HD 7700
Windows 10 v1803

System B
Motherboard: Asus Crosshair VI Hero
CPU: Ryzen 1800X

Sysem C
Motherboard: MSI X370 SLI PLUS
CPU: Ryzen 1700x
GPU1: EVGA GTX 1050 Ti
GPU2: EVGA GTX 1050 Ti

Monitors: Dell UltraSharp 24" u2414hb

KVM’s i have tried:
Vertiv Avocent 4-Port Dual-Head DisplayPort 4K Ultra HD KVM Switch (SV340D)
StarTech.com SV431DPDDUA2 DisplayPort KVM, 4 port, 4K 60Hz, Dual Monitor KVM, DisplayPort Switch
IOGEAR 2-Port DisplayPort 1.2 KVMP Switch with USB 3.1 Gen1 Hub and Audio (TAA Compliant) GCS1932

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You’d be surprised how many dp cables out there are crap. We will have some cheap but excellent cables on l1 soon. Try those.

I’ve also found some devices like 2013 mac pros spew way out of spec signals. Which wreak havoc with the l1 kvm. The fix is an active repeater with edid injector/corrector. I am prototyping those but I doubt there is much of a market for them and I’d have to sell them for around $50 each w/o a power adapter (USB for power works fine)


Thanks for the reply Wendell. At one point i was thinking i would need some form of “keep alive” between the system and KVM.

You mentioned the Mac and i have seen in a couple of the other KVM posts about people testing their connections. Is this a process us mere mortals can do? If so how would i go about testing my connections to see whats going on?

I will keep an eye on the cables in the store and pick some up and test them out when they are in.

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The linux amdgpu driver is pretty verbose about dp link failures and other dp weirdness. That’s something. Other than that it’s hard to do much without some basic equipment

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Just some anecdotal evidence. We had a bunch of dell monitors and a couple of the cables provided just refused to work with the DP version we wanted to use, or gave graphical glitches. New cables from a 3rd party worked instead, it seems they can be hit and miss.