Dual KVM HID and Display Issues


Recently purchased the Dual Monitor Dual PC KVM. When switching between my work laptop and PC, my displays work with the PC but only the 1440p display works with the laptop. Conversely, my HID devices work with my laptop but not my PC. Below are pictures of my cable setup.

I tried unplugging everything, powercycling the KVM, and then plugging everything back in to no avail. I’m pretty new to tech so any and all advice is greatly appreciated.

the usbc cable on the dp 1.4 dual monitor kvm cannot do both usbc and displayport. you need a usbc to displayport cble going into the empty pc2 port for displayport.

similiarly pc1 doesn’t seem to have a usb port

this kind of kvm each pc needs:

display 1
display 2

discreet connections from each device. If you have a usbc pass-through hub that does ub and display, that’d probably work with your laptop if it only has one usbc port. otherwise a moshi brand usbc to dp cable from the laptop should fix it up.

the hid devices will work with the desktop when you use a C to C or C to A usb cable to connect the usb port on the kvm to your desktop pc.

Hi wendell, thanks for responding! does the cable need to be moshi brand? would another bidirectional USB-C to DP cable work? $60 seems very steep.

Usually yes but occasionally some people complain that certain USBc to dp cables mishandle sleep or other modes. Try a cheaper cable and let us know it works, and wake from sleep works?

I’d just go with the dock option. Bonus of less plugs to mess with, assuming the laptop gets moved around.
Charger, dock, done.
Plenty of those exist for way less than $60.
If I’m understanding right (pretty sure I am) KVM won’t do the appropriate signal muxing, but a simple type C dock will, with zero disadvantages vs a C to DP cable.
Not sure how many cheap docks have DP instead of HDMI though. Likely some used OEM bundled option to be had cheap used. Personally bought a Thunderbolt 3 dock used for $16 about a year ago. Never got to test it; bought a random thunderbolt card hoping I’d get it working on a PC… nothing else I have has thunderbolt.

EDIT: And since you’re new, be aware that a laptop with thunderbolt 3 can use a thunderbolt or USB C dock, but a laptop without thunderbolt can only use the USB type C dock. … and that type C rabbit hole goes much deeper.

Hi Wendell, I purchased the Moshi Cable and have a unique situation now. The Moshi cable brought up the refresh rate on my 1440p monitor up while using it with my laptop; however, while on my PC both monitors work with max framerates, the 1080p monitor does not work on my laptop. Tried swapping the cable orders and power cycling then plugging everything in one at a time after. Do you have any suggested fixes?

Wait…are you HDMI dp HDMI for one monitor? If so don’t think that’ll work because of how the adapters work under the hood? It might work if they are both externally USB powered/both active. If it doesn’t source power from somewhere its not active

Technically not that simple.

To translate for a noob. The DP from first adapter would need to support DP+, a standard for ‘passive’ conversion, or the adapter from KVM’s output would need to be an active converter. Surprised I didn’t think of that.
If that laptop has thunderbolt, just get a dock; easy to find ones that have multiple DP ports. If it’s just Type C altmode, be ready to hunt for the right dock, or hunt for an active adapter out of KVM. Startech is probably a good brand to start looking at.

Hi Wendell, If I just changed my 1080p monitor to a DP one, would it fix this issue? That would get rid of the passive adapter, leaving me with only the active adapter attached to my laptop.

Seems pretty likely

Borrowed a DP monitor from a friend and it did not fix the issue unfortunately. ready to give up at this point. do you have any last shot suggestions?

The 1080p monitor replaced with a dp monitor doesn’t work? Dodgy dp cable then. Moshi USBC to native DP monitor should for sure work fine if that’s what were still testing

so i finally got it to work. it wasn’t a cable issue (all my cables are from infinite cables and 6 ft or under). i unplugged one of the DP cables that runs to my PC from the KVM while it was displaying my PC, switched to the laptop, and it worked. plugged the cable back in and it still works. flabbergasted that this worked. it does seem like you can’t use a passive adapter to connect your monitor to the KVM. omw to buy my own DP monitor to return it.

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A fucking dock.

Are you keeping the total run length below 4m? This means from the output on the laptop to the input on the monitor, add up the total length of all the cables in that signal path. If you get more than 4m, that could be your problem. I usually add 0.25m for each “device” in the signal path, so KVM, dock, adapter, etc…

I’ve found that using this path: monitor → 2m cable → kvm → 2m cable → laptop dock → 1m cable

Was too much for it, but if I switched out one of those 2m cables to a 1m, it suddenly worked, even if they’re from the same manufacturer (club3d has my undying adoration for their top-tier quality)

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Well, a dock creates the signal, so adding anything based on that…

Does it?

My testing has indicated otherwise, at least with the belkin TB3 dock I’ve got on my desk. When plugging in my framework direct to displayport, the signal worked, when plugging it into the dock, and the displayport into the dock, it did not work until I reduced the run length of the displayport cables.

That dock has a weaker signal than that laptop.

For you AND anybody else reading, yes. GPU creates the data, thunderbolt shuffles it around, then dock reshuffles the data into a usable signal.
I suppose type C doesn’t. That a good point of clarification. Dude never said if he has the option on his laptop.

Thanks for clarifying, I never really cared to look into it. USB C docks probably use MST or displaylink, but I guess it makes sense that thunderbolt docks have a different process.