Monitors flicker at 144Hz using CalDigit TS4 Dock with KVM

KVM Model:

1.4 DisplayPort KVM Switch - Dual Monitor - Two Computer (SQ1007387)

USB Interface (5-gigabit or 10-gigabit):

10-gigabit


Setup:

My desktop is connected to the KVM via two +/- 1.5 m DisplayPort 1.4 cables (which I received with my monitors).

My work laptop is connected to a CalDigit TS4 docking station, which is then connected via two 1 m DisplayPort 1.4 cables (Amazon Basics). One of these cables uses a Ugreen DisplayPort 1.4 to USB-C adapter to connect to the docking station, while the other cable is directly connected to the docking station.

The KVM itself is connected to my two monitors (LG UltraGear 27GN850-B) via two 2 m DisplayPort 1.4 cables (Amazon Basics).

Problem:

About a month ago, I purchased the KVM (DP 1.4, Dual Monitor, 2 Computer). I want to connect it to both my desktop and my work laptop.

My monitors flicker when I use my work laptop if the refresh rate is set to 144 Hz. However, I do not experience this issue at a refresh rate of 120 Hz.

When using my desktop at 144 Hz, I don’t encounter any problems.

After reading some topics on this forum, I was confident that this is a bandwidth issue. This could be related to the quality of the cables I’m using. To resolve this, I ordered the recommended cables from Club3D (2 x 1 m and 2 x 2 m). However, after replacing my Amazon Basics cables, I am still experiencing the same problem…

I am quite at a loss. At the moment, I don’t know what the root cause could be. Are the cables too long? Is the KVM compatible with the CalDigit TS4?

Can anyone help me?
Thanks in advance!

generally ts4 works ok. I suspect the thunderbolt cable based on what youve said. can you try some different thunderbolt 4/5 cables and see if that has any effect? especially shorter ones. iirc 144hz needs dsc or 420 chroma on macs and macs are weird about dsc support.

check also the osd of the display to see if you have any energy saving or dp handshake options you can toggle to see if it makes a difference. thunderbolt isn’t that much bandwidth you might be right up against the limit of USB+dp bandwidth over the same wire.

Hi Wendell,

Thank you for your quick response!

I took a look at my monitor settings. I found and disabled the energy saving setting, but unfortunately, that didn’t help. I couldn’t find a DP handshake setting.

I forgot to mention earlier that both my desktop and work laptop use Windows as their operating system. My work laptop runs on Windows 11, and my desktop runs on Windows 10. So, I don’t think DSC support should be an issue.

Thunderbolt 4 bandwidth could indeed be a potential cause. However, the combined bandwidth of my monitors is around 30.6 Gbps. Even when factoring in the bandwidth used by additional USB devices, I should still be below the 40 Gbps limit of the Thunderbolt 4 specification. In the meantime, I’ve ordered two Thunderbolt 5 cables: one 0.5 meters and one 1 meter. I’ll test them as soon as they arrive!

Additionally, I tested another option I had previously overlooked: connecting the CalDigit TS4 directly to my monitors. I had bought both the CalDigit TS4 and the KVM at the same time, but I had never connected the TS4 directly to my monitors. While I did test my laptop directly connected to the monitors using the Amazon Basics cables, I hadn’t tested the CalDigit TS4 in the same way. I’ve now tested it, and unfortunately, my monitors still flicker when the CalDigit TS4 is connected directly.

Hopefully, the issue lies with the included Thunderbolt 4 cable from CalDigit, and the new Thunderbolt 5 cables will resolve it.

So, I can confidently say that the issue is not with the KVM. Do you think there could potentially be a problem with my laptop (software or hardware)?

Thank you so much for offering a different perspective! I’ll test the new Thunderbolt 5 cables and reevaluate from there. If the issue persists, I’ll reach out to CalDigit support.

I’ll keep you updated!

Cables that come with monitors does not guarantee quality unfortunately. Replace these with the club3d cables?

Also, what monitors do you have?

Hi Amber,

Thank you for thinking along to find a solution to my problem!

The questions you asked have already been answered in my first message. Below, I’ll clarify them again for you.

I have replaced the cables with the suggested Club3D cables. However, I did not replace the cables that came with my monitors, as they are connected to my desktop, which does support a 1440p resolution with a 144Hz refresh rate. For this reason, I didn’t see the need to replace them.

These monitors have a resolution of 1440p and a refresh rate of 144Hz.

I hope this answers the questions you had. If you have any further questions or any possible solutions, please feel free to let me know!

it might be worth swapping the cable even though it works from kvm to monitor for the desktop.

the way these kvms work to not mess with freesync/gsync the monitors see all the cables in the chain like they’re one long cable. losses are additive. so you may have extra loss margin on the cable that you don’t need with the desktop but you do need with the laptop if that makes sense …