Linux and the UD-ULTC4K triple display dock

Greetings. This is both a review, and a question.

First the review. I know that the Plugable Triple Display USB-C docking station (UD-ULTC4K) is not officially supported for Linux. However I thought I would give it a try anyway. I’m pleased to report that, by and large, it DOES work with Ubuntu 16.04, WITH three external monitors.

My laptap specs are: Dell Precision 5520, with Xeon processor, and Intel HD and Nvidia GPUs, 4K touch sensitive screen.
OS: Xubuntu 16.04.3 LTS
External monitors: Three 1920x1080 HD widescreen Asus monitors, with HDMI and DVI connectors.

What worked right out of the box:

  • All USB peripherals, including USB3 external SATA hard drive, Logitech K800 keyboard and M705 mouse (both using a single Logitech Unifying USB receiver), flash drive, etc.
  • Ethernet adapter.
  • External monitor connected to HDMI port.

What needed a little work:
The other two monitors are connected to the DisplayLink ports using two Plugable DisplayPort to HDMI Passive Adapters. Those did work after I installed the latest Linux driver available from

The display on all three monitors was a little unreliable, requiring me to re-do the configuration after each reboot, and occasionally having unplug the dock, reboot, get the single monitor working again, plug the dock back in, etc. I finally found the problem was with the xorg hwe hardware stack. When I removed all the xserver-xorg…hwe packages and re-installed the older (non-hwe) xorg packages, things got a lot more stable. Reboots still occasionally fail to start a monitor, or maintain my arrangement, but from what I read that’s a common problem with Linux with multiple monitors. I fixed that by writing a short script using xrandr to reset my configuration after rebooting.

However, now we’re down to what doesn’t work. Basically there seems to be an upper limit to how many devices I can plug into this dock, and the limit is rather small. When I tried to attach my external Logitech C190 webcam, it would not fully function. The kern.log was full of messages saying, “Not enough bandwidth for new device state.” When I plugged the webcam into another USB port directly on the laptop, it worked just fine. It only fails with I plug it into the dock.

I’ve read other reports online that older USB peripherals will use too much bandwidth when plugged into USB3 docks. Is that what is going on here? If I only plugged USB3 devices into the dock, should I be able to attach more devices? (The keyboard/mouse receiver and webcam are both USB-2 devices.)

Right now the only things connected to the dock are the monitors, the Unifying receiver for the keyboard/mouse, and the wire to the external speakers. That’s not much. Adding anything else seems to overload the available USB bandwidth.

Overall I’m very happy with the dock. My major concern with moving from a desktop to a laptop as my primary machine was being able to support my three external monitors. If it does nothing else, the dock is worth it for providing that. (Note, this are only 1920x1080 monitors. I have yet to test adding three 4k monitors, since I don’t have any yet.) Still, I would love to be able to connect *everything* into the dock, and only have one thing to unplug when I want to take the laptop with me.

Any thoughts?

LB (Seattle, WA)

Hello Larry, thank you for posting! I am sorry to hear of the USB bandwidth issues you’re experiencing and I’ll be happy to help.

As you mention, we do not formally support Linux and to set expectations, I cannot guarantee we will find a solution but happy to help as much as I can to see if a fix can be found or if something can be learned.

A simple test, if possible, would be to see if the same or similar issue occurs within Windows if you happen to be dual booting on your laptop, but understood if that is not possible.

If you disconnect the other USB peripherals and only connect the Logitech C190 do you see the same bandwidth errors?

Additionally, we can examine some log files from our PlugDebug utility to see if anything jumps out to use. To help us do so please download and run our diagnostic utility PlugDebug –> and please send us the file created on the Desktop by sending them to our support email address at with ‘Ticket Number 213491’ in the subject line. We’ll examine the log file and go from there.

Thank you,

David W.
Plugable Technologies


Sorry for the late reply. Been unable to get back to this for awhile.

First, testing under Windows is not an option; the laptop is not dual boot.

I tried disconnecting all the external monitors. The only things plugged in were the ethernet, the keyboard/mouse receiver, and the webcam. Those all worked. Then I started plugging monitors back in. Adding the first monitor worked okay, but when I added the second everything went wonky. The monitors “worked”, but it appears they reverted to much lower settings, esp in terms of the RGB color spectrum. Icons reverted to much lower definition, and most of the colors went away.

I will try downloading the debug utility and run that next. Should I run it with the current setup (i.e. everything plugged into the dock EXCEPT the webcam), or run it with the webcam plugged into the dock?

Finally, I’ve discovered a new odd quirk. I *thought* that the sound was working through my external speakers plugged into the dock, but I was mistaken. I’ve discovered that the dock is sending all the sound over DisplayPort/HDMI to one of my monitors. Do you know how to get the dock to send the sound through the speaker wire, instead of through DisplayPort/HDMI?

Thanks so much.

Hi Larry, thanks for the reply and additional information. Please send us the log file with everything connected but with the webcam not working.

When Plugable Audio is set as the default audio device it will send audio over connected monitors, but once speakers are connected to the front audio ports they should take over. Does the same issue occur if you connect wired headphones? Just curious if this seems to occur regardless of headphones/speakers that are connected.

Thank you,

David W.
Plugable Technologies