**1.4 DP Dual Monitor / Four Computer**; docking station and HDMI

Hardware Hub Other Hardware
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Hi,

I recently bought a 1.4 DP Dual Monitor / Four Computer KVM Switch which I want to use to connect to four computers as below. But I haven’t been able to connect my computers to the KVM the way I had hoped yet. Due to some other circumstances, I haven’t been able to troubleshoot until now.

Computer 1 - Windows PC

Computer 2 - Linux server

Computer 3 - Linux desktop

Computer 4 - HP laptop via Lenovo Thunderbolt 4 docking station. Work equipment, not personal choice.

Computer 1 and 2 appear to work fine, though I haven’t been able to connect my Logitech webcam as HiD, but as normal USB.

My major issues are with Computer 3 and 4.

Computer 3

Computer 3 does not have any Displayports, only one HDMI-port and one USB C-port. I’ve tried using HDMI to DP cable from PC but I get no video signal. Since that doesn’t work so I am unable to test if anything else works

Reading through the guide, it seems like HDMI (from computer) to Displayport (to KVM) cable does not work. Is this correct?

Is the best option USB-C to DP cable? Otherwise, I need a HDMI to DP active adapter like the Club3D one you’ve suggested?

I did email Wendell about this before placing an order but only got reply to the first of three emails.

Computer 4

The connection is as follows: PC is connected to the docking station with a thunderbolt 4 cable. Docking station is connected to the KVM with 2 x DP cables and 1 USB C-cable.

I get very low screen resolution on one of the two screens. When I turn off the screen with proper resolution, the resolution is adjusted for the second monitor and becomes decent. I’ve tested different cables, including Club3D cables that work for Computer 1 and 2 but still can’t get proper resolution on both screens.

In addition, I can’t get the USB to work at all unless I connect the USB C data cable directly between the laptop and the KVM (i.e. skipping the docking station). Still, even with this setup, I can for example not get my microphone (HiD) to connect, even though it works with e.g. Computer 1.

Reading through other posts on the forum, I should be able to get decent resolution on two screens as well as USB to work with just one thunderbolt 4 cable from the docking station to the KVM. Any suggestions on how I can solve this? Any idea why I can’t get the USB to work with the dock?

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We had 1 guy claim he successfully got an active HDMI → DP cable to work, but I had not had any success with them. Yes, I would highly recommend an adapter like the club3d. HDMI requires an active adapter to be able to convert to DP.

Hm, both would work, I would probably suggest the active HDMI → DP. Also, the USBC → DP cable is currently unavailable on Amazon (US)

Hmmmm. Since this is your work equipment, are there any restrictions…? I know many people use feeders and EDID work arounds for their work locked down laptops/thin clients

@wendell do you know why this might be?

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use the docking stations downstream thunderbolt port with the kvm, this is a mac thing. then it should work. if its a caldigit dock it for sure works fine this way.

an active hdmi to dp adapter can work? usbc to dp display port cable is usually a better option, tho depends somewhat on the setup you have.

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The USBC → DP adapter we’re talking about is this one: USB-C to DisplayPort Cable – us.moshi (US)

^ Oop, Wendell said it’s usually the better option so just ignore me xD

Lmk if the downstream thunderbolt port option works

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Anything to think about when selecting a USB-C to DP cable? I live in Sweden so my options are slightly different. I may be able to get hold of a Moshi cable.
I’m not really sure how I would connect a HDMI to DP active adapter between the PC (HDMI) and KVM (DP). Where would the USB cable go?

Connecting to the thunderbolt downstream port was the first thing I tried and it deosn’t work with a 10 GBPS cable. I can try with a thunderbolt 4 cable but I would have to buy one (pretty expensive) and I don’t see why that would be necessary. A 10 GBPS cable should be sufficient for the USB to work.
As mentioned, the hardware here are HP laptop and Lenovo Thunderbolt 4 docking station.

I can barely do anything fun with the work equipment. Installing anything is pretty difficult without a bunch of phone calls across the globe and some social finessing locally.

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Whats the actual docking station? Try a short cable from dock to computer?

sorry, was on mobile and autocorrect has a mind of its own.

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Lenovo ThinkPad Uniersal Thunderbolt 4 Dock.

Sble? I’ve tried both USB A-USB C as well as USB C-USB C cables but it still doesn’t work unless I connect the laptop directly to the KVM for USB (while displayports still run through the dock), even though those cables work when I connect them to the other computers and support 10gbps

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There is literally nothing in the KVM that can cause it to behave this way. Macs do this thing with “USB Hub Depth” where they explicitly don’t like daisy-chained usb hubs, but this is still technically not a KVM thing. Perhaps your work machine has some bizzaro-land “no daisy chained USB hubs” type setting? Is there a firmware update for your dock? The usb part of the kvm is not particularly exotic.

You could try to unplug the kvm from power for a minute or so as it does have an internal memory about devices, topology, and mapping… that it remembers in an effort to juggle connections into a state that is reasonably the same between all the connected host PCs. This is not likely to be a source of “the ports don’t work at all” type situations, however. Plus rebooting the KVM should clear that memory anyway. There is also over-current protection wherein it won’t enable a device that wants too much power. But rebooting the kvm clears that as well.

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I need DP alt mode on the pc for this to work, right? I don’t have that.

So will try with the Club 3D CAC-2330 HDMI 1.4 to DisplayPort adapter. So I plug the HDMI and the USB from the adapter into the computer and the DP female from the adapter to a DP cable that is connected to the KVM? The USB is only for power?

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I have a similar problem with the resolution on a linux laptop (haven’t tried USB from monitor actually).
(Thinkpad L15 on Dell docking station - without a kvm in between)

Both monitors are ThinkVision P27h10.
Only of monitor can make use of 2560x1440, the other can only be 1920x1080.
When configuring the second monitor to 2560 the desktop extends above the screen itself and get cut off at the bottom and one side.

I tried out every possible combination of cables and monitor configurations. I have not found a solution yet.
The docking station doesn’t seem to be the problem as it works fine on my work laptop running windows.

But what I couldn’t rule out yet, is the way my distro handles this stuff.
Running stock Ubuntu right now. Might be a gnome (more specific: mutter) issue. For this and other reasons I might switch in the near future.

May I ask what distro (/DE/WM) you are running on this device?

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