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Whenever I connect my MBP to an external monitor via a DisplayPort cable the OS pretty much locks up.

I have a new 2020 13" MBP running Catalina 10.15.5 (19F101). I'm trying to connect it to an external monitor via a Caldigit USB-C Pro dock and a 6ft DisplayPort <-> DisplayPort cable. When I connect the cable to the external monitor the laptop freezes for about 10-20 seconds, then the display updates momentarily, then freezes for another 10-20 seconds, then updates, and so on. The external monitor says it's not getting a signal. If I unplug the DisplayPort cable (either at the dock or at the monitor) then the laptop goes back to normal after a few seconds.

What can I do to diagnose this issue further? I've tried running Activity Monitor and I don't see any noticeable spikes in resource utilization.

I thought maybe the issue was with the cable - perhaps I need an "active" cable rather than a "passive" - but the Caldigit documentation only says that's necessary for an adapter (i.e. DisplayPort to HDMI).

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2 Answers 2

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The dock has two DisplayPort ports, which are not present in the USB-C cable, so the hub must have some extra hardware providing this.

This may require drivers. I have a Thinkpad USB-C dock home from work these days (corona) which require a DisplayLink driver installed on my Mac to provide video output from the dock. It might be something similar here.

I would suggest reconsidering your Hub choice. A simple solution may be the USB-C Digital AV Multiport-adapter (https://www.apple.com/dk/shop/product/MUF82ZM).

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  • Thanks for the driver suggestion. Unfortunately I tried downloading and installing the driver that Caldigit have on their support page and it didn't seem to help at all.
    – Pete Hodgson
    Commented Jun 8, 2020 at 4:40
  • May not be Mac compatible then. Try an official apppe adapter instead.
    – Thorbjørn Ravn Andersen
    Commented Jun 8, 2020 at 7:04
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The dock you have chosen should work perfectly well with your computer.

Contrary to what the other answer given states, the dock is actually a Thunderbolt 3 AND a USB-C dock. As long as you use an appropriate Thunderbolt 3 cable (like the one that comes with the dock), it will use a full Thunderbolt 3 signal to communicate with your computer - not USB-C.

This means that two DisplayPort outputs is fully possible without using DisplayLink or anything like that.

In terms of diagnosing the problem you have, I would suggest starting with a new DisplayPort cable. An issue like the one you describe can come from a defective cable. Remember if you use any type of adapter cable (like for converting to HDMI), it must an active adapter - not a passive one.

If replacing the DisplayPort cable does not work, I would try it with a different monitor.

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