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I currently own a 2017 MacBook Pro (13", four Thunderbolt 3 ports) and a Dell P2415Q. I'm strongly considering purchasing two more Dell P2415Qs so that I can have a triple-monitor setup, but I only have one free USB Type-C port when docked right now. I also know that the Dell P2415Q's daisy-chaining capability isn't supported by OS X.

Is there a device I can purchase that will allow me to provide full charging power to my 13" MacBook Pro and allow me to plug three Dell P2415Qs into it (at 4K@60hz), all going into the MacBook via a single Thunderbolt 3 / USB Type-C cable? (If not, can it be done with only 2 TB3/USBC cables?)

My specs are:

  • 13-inch, 2017 MacBook Pro with four Thunderbolt 3 Ports
  • 3.5GHz Intel Core i7 CPU
  • 16GB 2133 MHz LPDDR3 RAM
  • Intel Iris Plus Graphics 650 1536 MB
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3 Answers 3

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No. Thunderbolt 3 doesn’t chain video, just the thunderbolt data. What protocol you are feeding to the display and the diplay size will limit your options.

For example, the LG 5k displays are thunderbolt and you get two, one on each side of the MacBook Pro. HDMI adapter might let you chain a second display from a primary display based on the quality of the hub and the resolution on both, but I am 90% certain that won’t work either. Plan on one display per physical port on the Mac.

Now, some displays will mirror the same DisplayPort stream apparently. I haven't seen this but have no reason to suspect these reports aren't 100% correct.

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  • Even without chaining, is there some sort of Thunderbolt 3 "dock" or "splitter" I can use?
    – Kerrick
    Commented Nov 18, 2017 at 1:05
  • @Kerrick. My understanding is only one DisplayPort data stream leaves the Mac per port, so no. The protocol does daisy chain, but data and power chain, not video. You lose all downstream video when the first display gets connected in the chain. So place the display after any drives or hubs or such.
    – bmike ♦
    Commented Nov 18, 2017 at 1:06
  • @Kerrick I've upvoted this answer as I agree with bmike that you should plan on one display per physical port on the Mac. Any third display will have to use HDMI etc and will be hit & miss as you couldn't guarantee it'd work, as some displays don't play nicely with some adaptors. I recently helped a lady with the same MBP but with another Dell screen (it was a 27" though) and we had to try three adapters before finding one it would work with (it didn't work with the official Apple one either). Anyway, in a nutshell you can't do what you want with a single cable, nor with a single dock/hub.
    – Monomeeth ♦
    Commented Nov 18, 2017 at 1:36
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Official Apple specs

Officially your MBP supports two external displays at up to a maximum resolution of 4,096 x 2,304 pixels at 60 Hz at millions of colours or a single external display at a maximum resolution of up to 5,120 x 2,880 at 60 Hz at over a billion colours.

So, running the two external displays along with your built-in display is officially supported.

Unofficial real-life scenarios

However, unofficially you can exceed this. More specifically I've seen a user connect three external displays while in clamshell mode. However, this did seem to result in the MBP's fans spinning at a higher rate when they were watching videos, playing games, etc. Not something I would really recommend.

Your setup

So, I wouldn't recommend three external displays. But, as for your setup, you say that you only have one free USB Type-C port. So for you to do what you want may require you using your ports differently so that you have at least two displays connected directly, and another different display connected via an adapter and your other devices connected via a dock or hub.

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  • I agree, hang the usb devices on the display ports (get one with a hub integrated) or use the fourth port for a dock / hub.
    – bmike ♦
    Commented Nov 18, 2017 at 1:11
  • Can I use a third display with an external video card?
    – Vitaly Zdanevich
    Commented Feb 5, 2018 at 17:46
  • That would depend on your computer, the eGPU in question, and your configuration. But, yes, certainly this would be a possibility. You'd probably want to weigh up at what point you're better off investing in a different computer, but an eGPU may make perfect sense for you.
    – Monomeeth ♦
    Commented Feb 6, 2018 at 3:51
  • I'm trying to run 1x4k and 2x1080p (2k) screens off of one port. Clearly the data isn't an issue because two 1080p screens are half the bandwidth of a single 4k monitor (1x4k = 4x1080p), and a single port supports two 4k monitors. What I'm wondering though is if there's a physical limitation to the number of monitors. In other words, I can't drive 8 1080p screens on a single port because of the limitation on the number of streams, right? (I'm trying to use a TB3 dock that has DisplayPort and TB3 out and I'm wondering if I can plug a TB3-to-2xHDMI (1080p) into the TB3 port.
    – Mark A. Donohoe
    Commented Aug 11, 2018 at 0:31
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Can I connect three monitors and provide power to my MacBook Pro with a single cable?

Yes.

There are eGPUs capable of driving at least three 4K displays while supplying power to the MacBook on a single Thunderbolt/USB-C port.

Examples of such products here: https://www.sonnettech.com/product/egpu-breakaway-puck/overview.html

A PCIe expansion chassis with a graphics card or two will also work: https://eshop.macsales.com/item/AKiTiO/3N2AA0002Y/

I'm seeing 60 watts supplied to an attached MacBook as quite common, if this is sufficient power to avoid needing a separate power supply on a second USB-C port depends on the model of laptop and computing load. Taking some load off with an eGPU should help in lowering power consumption. Finding an expansion chassis or eGPU that supplies more than 60 watts may be difficult. I expect this to change as more MacBook models come out that consume more than 60 watts.

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