Slow Monitor Connection

USB-C 4K Triple Display Dock
MacBook Pro 2016 Touch Bar
ViewSonic VP-2 780-4K Monitor
DP to Mini DP Monitor Cable
Gigabit ethernet and sound connected
External DVD drive connected to USB-3.0 port but not being used
Drivers 4.1.11

Docking Station Performance:
Parallels 13 window mode noticeably sluggish
Parallels Coherence mode does not work at all

Parallels performance is fine when monitor is connected to Thunderbolt 3 port on docking station, both in Window and Coherence modes.

Hi Tony,

Thanks for posting, and thank you for the great detail you provided about your setup!

Based on your description of the Parallels behavior, two quick questions for you:

  1. Is your MacBook Pro running the latest release of macOS, version 10.13.3. High Sierra?

  2. If you connect the ViewSonic monitor to the Plugable dock’s HDMI output, does that help improve the performance?

Thank you,

Plugable Technologies

Thanks for getting back to me quickly.

I keep my OS current, though I am not a beta tester so I am only up to version 10.13.2. I am also current with the latest retail releases for Windows 10 and Parallels, including all security updates for Windows 10.

The HDMI suggestion cleared up the coherence failure but it is still as sluggish.

I have reverted to driving the monitor with a TB-3 to DP cable which, for now, is my gold standard for comparison. I don’t think it will matter but the HDMI cable I used is Version 1.0. I have a version 2.0 cable coming tomorrow.

Though I suspect that Parallels SW is factoring into this issue, I haven’t been able to find a combination of cables, Mac Video settings and Windows 10 video settings that produce acceptable results through your device. Would it help with trouble shooting to to send you a Mac systems support? Your support interface doesn’t seem to have a way to upload anything but images.

I was lead to believe that the USB0C 4K docking station would work for me. Should I have purchased the TB-3 station or do you think we will be able to resolve this at some point?

Hi Tony,

Thanks for getting back with the update. A quick note in regard to macOS version, 10.13.3 was released on Jan. 23rd as a stable release ->

When the display is attached to the HDMI output of the dock, the output is powered by the USB-C Alt Mode video output provided by your Mac’s Thunderbolt 3 port so it should provide for ‘native’ performance.

However, when connected in this manner the refresh rate of the display will be limited to 30Hz (half of the typical 60Hz) so that may account for the sluggishness you are describing.

When using the USB-C to DisplayPort cable you mention having directly connected to the Mac, the refresh rate will be 60Hz so that may explain the difference in behavior.

To help determine if this in fact the case here, if you connect the LG monitor to the dock’s HDMI output and temporarily lower the resolution to 1920x1080 (which will refresh at 60Hz) does that help with the behavior?

Thank you,