I plan to run a MacBook Pro (13-inch, 2017, Two Thunderbolt 3 ports) with two external UHD screens 3840 x 2160 at 60Hz using a dock.

My desired setting is:

Screen: LG 27UL850-W-4K https://www.lg.com/us/monitors/lg-27UL850-W-4k-uhd-led-monitor Dock: OWC thunderbolt 3 dock (https://eshop.macsales.com/shop/docks/owc-thunderbolt-3-dock).

According to Apple, this MacBook suppors two external Monitors up to 4K (https://support.apple.com/kb/SP754?locale=en_US)

Up to two displays with 3840-by-2160 resolution at 60Hz at over a billion colors

I found some posts reporting problems with dual external monitor settings with

  1. the same screen https://discussions.apple.com/thread/250066564
  2. other screens Dual monitor flickering: the secondary monitor does the flicker


  1. Should this setting run stable office work (Word, Excel) and video?
  2. Which cable and port do I have to use to connect the thunderbolt 3 dock with the monitors? Dual External Monitors on a (late) 2017 MacBook Pro mentioned:

Monitor A: Connected to mini-DisplayPort port Monitor B: Connected to daisy-chain Thunderbolt 3 port

I am not sure what is meaned with B. Could I also connect each screen with one of the TB3 of the dock? If yes, would a TB3 -> HDMI or TB3 -> DP cable lead to a better result?

This question is similar to Dual 4K monitors with 2017 Macbook Pro base model, however more specific.

1 Answer 1


In regards to question 1: Yes, it should work perfectly fine for those purposes. I use the same dock and similar 4K monitors with several setups here with the 2017 15" MacBook Pro without any flicker issues or similar. It should be the same for the 13" model.

In regards to question 2: The dock has a mini-DisplayPort port as well as a Thunderbolt 3 port for display output. The monitor has HDMI as well as DisplayPort inputs.

I would recommend using a mini-DisplayPort to DisplayPort cable for one monitor, and a Thunderbolt 3 (i.e. USB-C connector) to DisplayPort cable for the other monitor. I use these cables myself.

The meaning of "B" is that one Thunderbolt 3 port on the dock is used to connect to the laptop, the other Thunderbolt 3 port is connected to the monitor so it is "daisy-chained". Essentially this just means that the monitor signal for the monitor travel through the Thunderbolt cable from the computer to the dock, and is then passed on from the dock to the monitor.

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