Diagnosing macos locking up when external displayport monitor connected

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).

Solution 1:

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).