Thunderbolt 3 Docks - multi-display doesn't work in MacOS but does in Win10 on same hardware

Number:rdar://51317108 Date Originated:5/31/2019
Status:New Resolved:
Product:macOS + SDK Graphics & Imaging Product Version:
Classification:Bug Reproducible:Always
Two common Windows TB3 docks are:
- HP Thunderbolt G2 dock
- Lenovo Thinkpad TB3 Dock

In our investigations and testing, the majority of the functionality of these docks work great in MacOS, EXCEPT connecting multiple displays through them.
In the HP Thunderbolt G2 dock, there are 2 DisplayPort ports. If we try to connect two DisplayPort displays, only 1 works.
We have confirmed that if you install Windows 10 in Bootcamp on the Mac, you can connect two DisplayPort displays, and both work in extended mode or mirrored mode.

This appears to be a limitation of MacOS, not the hardware.

Steps to Reproduce:
Connect HP Thunderbolt G2 dock, and two monitors via DisplayPort
Try to extend desktop across both displays.

Expected Results:
Desktop extends across Mac display, and two external DisplayPort displays.

Actual Results:
Desktop extends across Mac display, and one external DisplayPort display.

Confirmed this occurs in all versions of MacOS including 10.14.5 (latest at time of submission)

MacBook Pro (15-inch, 2016)


Please note: Reports posted here will not necessarily be seen by Apple. All problems should be submitted at before they are posted here. Please only post information for Radars that you have filed yourself, and please do not include Apple confidential information in your posts. Thank you!