Progress Report:
MacMini back working on Port 1
Desktop/Laptop on 3/4 are behaving much better.
Update
Black screen flickering and dropped signals when port/input switching has returned, even though I have ferrite cores everywhere with external shielding on both of my HDMI cables on PC #1.
Upon taking another look, I figured it wouldn’t hurt to add a ferrite core on my Anker USB hub cable at the KVM end which sits right below my PC #1 input. This aggregates the FiiO DAC, Rodecaster Duo audio interface, and my Corsair keyboard.
After adding the core…the black screen flickering has stopped (so far), and input switching appears to be more stable between Ports 1+2. Will monitor for a few days and report back.
@wendell - Is it possible the above setup (prior to adding the core) brought noise on the USB line which made it seem like the interference originated from “inside the house” after exhausting all options on the HDMI side?
@kaiserbeto - Do you also have a USB cable/hub plugged into the rear port next to the PC #1 input?
I also have a self powered Anker USB hub (a bit different than yours) plugged into the same USB port on the KVM which aggregates my Microphone, camera, and Soundbar
I ran into a couple flickers today and I had to reseat one of the HDMI cables to my laptop. The problem has certainly improved since moving my devices to ports 3/4, but not gone away entirely.
I’ll put a ferrite core where you suggest – that’s a really good callout and discovery @Pudge
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Update:
This is a night and day level of difference after moving to ports 3/4 and adding a ferrite core to just about every wire and cable and within 300 yards of the KVM. 
@wendell Your product team should consider including a dozen of these with every purchase or at least including “add a ferrite core, or 50, if you experience severe flickering and dropouts” in the manual’s troubleshooting steps.
I’m going to switch back to ports 1/2 now that things are mostly stable after adding the ferrite core onto the USB hub cable … and see what happens.
I’m sort of blown away the USB hub is causing that much interference! it maY still not work just because internally those ports are closer to the USB control.
and two people have the same problem … from the same hub. at once.
You are correct, the black screen flickering and dropped input signals have returned again. Is there anything else we can try? I feel we have exhausted all options here, just at a loss for what the root cause could be (from an interference perspective).
I’ll move my work laptop from Port #2 to Port #3, which sits next to my Mac mini M4 on Port #4, leaving Port #2 open. We’ll see how that goes for my problematic Port #1 over the next few days
I’ve encountered similar issues where a cable is fine by itself but going through a KVM or similar device like capture splitter, it doesn’t. But changing quality/brand of one or both of cables fixes the issue.
Shame NVIDIA doesn’t have a method of correctly testing a cables bandwidth stability because I suspect when it says 48Gbps, it doesn’t reflect on noise/stability.
You can get cable analysis tools for HDMI which may help identifying lower quality cables, but that’s such an annoying expense to have to buy.
Also I would try to limit your total cable length as much as possible from PC-KVM-MONITOR.
Yeah I started using Ruipro fiber cables, then migrated to using certified HDMI 2.1 copper, with lengths of 9 feet total (PC->KVM->Monitor).
I also did some additional cable management cleanup and separated potentially “noisy” cables via speakers, DAC, charging bricks, etc., away from my HDMI cables. Even with those improvements, I’m still getting the same issues every day but not as much as before
My long and short of this is …
- the bajillion ferrite cores made a big difference and improved the problem.
- I moved the Windows devices to ports 3/4 and the problems went away virtually entirely.
- I moved the Windows devices back to 1/2 and the problem got worse again
- I then moved the devices back again to 3/4 and the problems have gone away, completely (sometimes it takes a long time (10 seconds?) for t he Desktop to negotiate, but it always does and never fails the handshake)
I guess I could go try another self powered USB hub… but I have a hard time accepting that moving the HDMI cables 2 inches to the left is the differentiator here as far as external interference goes. Especially since the USB cable has a ferrite core attached to it as well.
Is it possible ports 1/2 are “broken” ?
are ports 1/2 not shielded internally?
Is there that much interference coming from the USB Hub uplink cable?
Is there an overall design defect we’re hitting? (just asking – not accusing or pointing the finger unconstructively)
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I moved PC #1 (gaming desktop with the black screen flickering) to PC # 3, my work laptop from PC #2 to PC #4, and my Mac mini M4 to PC # 1. We’ll see how that goes over the next few days
I wouldn’t have thought so before today, but at the same time, this level of insanity hasn’t come up before. It’s probably no a coincidence you both have the same USB hub, though. If it’s within fcc limits it shouldn’t be a problem. Lol
It’s possible, I suppose. The whole reason wifi used to cut out when using 5gb usb on laptops when it first appeared was RF interference from the usb. In that case it wasn’t really a defect per se just a weird interaction. Its not atypical that we have a LOT of people using similar configs and its not really been an issue till now.
I will probably have to try to buy one of those USB hubs, set it up in Steve’s old sound chamber, and see if I can measure the RF.
The 1/2 problem is just physically closer to the usb hub than 3/4 and RF falloff via inverse square does make a big difference in practice.
Its for sure something I want to look at. I don’t know if a replacement kvm would fix it, but willing to try it. the chips that handle 1/2 are physically isolated from 3/4 so there is also chip-to-chip variance
…but the commonality of usb hub is super super interesting
I’ve unplugged the Anker hub for a couple days and unfortunately I’m still getting flickers. it got much better for a while, and then as usual, after powering the devices off, rebooting, installing an update or two, it went back to the same behavior.
Laptop HDMI cable has to be reseated once a day or so to properly negotiate. From there it’s random flickers here and there throughout the day on both Windows desktop + laptop.
I think the Anker hub was just a red herring, unfortunately.
Thoughts on how to proceed next?
I bought two other brands of USB hubs but unfortunately still had the same results. Was hoping the Tripp Lite hub with aluminum housing would do the trick, but to no avail.
I will say though…moving both of my Windows systems to Ports #3 and #4 has drastically improved my experience like yours did @kaiserbeto and only had like 1-2 flickers over the span of a few days. Moving them back to #1 and #2 brought back the same constant daily flickering and increased dropped signal upon switching.
@Level1_Amber - I’ll submit a RMA this weekend
@wendell - Prior to sending the unit back, is there anything Level1Techs can add inside to minimize EMI/RFI near Ports #1 and #2? Or would that not be a feasible approach? Just not sure what else there is to try here
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It’s uncanny that we are having almost the same exact experience given that our workstations, cabling, office setup and ancillary equipment, geographic regions/home setup, etc are all completely different.
Seems like the commonalities here are:
- MSI brand monitor (different models)
- KVM
- Windows OS
- Nvidia GPU (different models)
- Moving to ports 3/4 drastically improves the experience
Does this help us narrow down the issue at all @wendell ?
probably mail in rma? I’m still a bit sus that the USB hub was also a commonality. and those can be a known source of interference
thanks @wendell – I’ll fill out the RMA form. Just a quick reminder in case that detail was missed, I had the USB hub and associated devices (camera, sound bar) fully powered off for several days and ports 1/2 were completely unstable.
Thanks
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Shipped out my RMA last night. I’ll swap to the DisplayPort 1.4 KVM and see if that resolves the issue