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NUC10i5 Black screen via displayport when connecting (audio/video) USB devices


I have two Dell monitors connected (in series) using Displayport via the USB-C connector to my NUC10i5fnh.

As soon as I remove or add a webcam or microphone my two monitors goes to sleep because of lost signal. This also happens when I start Skype (because it accesses the webcam?).

Unlike what others here have described, my monitors does not come on again, and they don't just flicker, they loose signal and thus goes to sleep.

My workaround is to disconnect and reconnect the USB-C connector, works every time but is really annoying...

I'm running Windows 10 and have latest BIOS. Also tried uncheck "Allow the computer to turn off this device to save power" in the Thunderbolt Controller.

Any suggestions appreciated.


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Super User Retired Employee

You have two monitors daisy-chained to the NUC. What kinds of monitors are these? How exactly did you connect these two monitors to the NUC? You've said the second monitor is daisy-chained off the first, but nothing about how the first monitor is connected to the NUC. Did you use a USB-C-to-DP cable/dongle to connect the first monitor? Did you use a USB-C-to-USB-C cable to connect the first monitor? Do you perhaps have some sort of dock or multi-port device? If so, does this device use Thunderbolt for the NUC connection?

If the USB-C connection is not via Thunderbolt, then the DP bandwidth available (via DP Alt. Mode) is 4K@60Hz. This bandwidth level is available because the DP connection can use all 4 of the USB-C lanes  If the USB-C connection is also supporting USB devices, however, then the DP bandwidth available is only 4K@30Hz. In this case, the bandwidth has dropped because the DP connection can only use 2 lanes.



I have a USB-C to Displayport cable from the thunderbolt connector on the NUC to the first Dell monitor (U2515H). Then another Displayport to Displayport cable to the second Dell monitor (U2412M). I have also enabled DP 1.2 on the first monitor in order to get a picture on the second monitor. No docks or multiport devices in between. The USB gear is connected to the USB 3 connectors on the NUC.

However, I have now tried some more, and right now I can no longer reproduce the problem. I'll investigate some more if I have received any Windows updates lately...

Super User Retired Employee

Let us know. In theory, plugging in a USB device in to one of the other USB3 connectors should not affect the monitors when used in this configuration.



A quick follow-up... It seems I got an "Intel Graphics" update via Windows around the time my problem stopped. I have not seen my original problem since my last post so I'll declare this resolved for now.

Thanks for your help.