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Wraithbone

macrumors newbie
Original poster
Apr 14, 2010
18
14
Hi everyone

I hoped someone in here would be able to test if apple made Mac OS 11 support Multi-Stream Transport (MST) for thunderbolt based docking stations. Basically, does it support two screens with a thunderbolt dock that only uses MST? The hardware supports it, but until now the software is the actual limitation.

Its rather specific, but I hope someone out there knows what I am talking about here.
 

jonasneve

macrumors newbie
Jun 25, 2020
3
0
I am hoping for the same thing. I have two Dell U2520D's 🖥 🖥 and what to run them on my MacBook Pro 💻 via a single USB-C and connect the two monitors via the DP output/input, works fine on PC, but MacOS won't connect the second monitor 🖥 ❌ 🖥 , so Im running them with two USB-C as of now. I really hope Apple opens it in Big Sur 🤞
 
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anshuvorty

macrumors 68000
Sep 1, 2010
1,705
1,516
California, USA
I can't answer the question about 2 monitors with a Thunderbolt dock. But I can answer your question about 1 monitor connected to a Thunderbolt dock.

I have a 16-inch 2019 MacBook Pro that is connected to a Belkin Thunderbolt 3 Express HD Dock. Everything with the dock works except my monitor which is connected to the dock through DisplayPort on macOS Big Sur Dev Beta 1. In order to get my monitor working with macOS Big Sur, I have to use a USB-C to HDMI adapter and connect to my monitor through the HDMI port on my monitor and on another USB-C port on my laptop directly.

The dock works perfectly in macOS Catalina 10.15.5, so I am guessing there is an issue with the Thunderbolt 3 driver in macOS Big Sur.

I am making an assumption here, but because 1 monitor is not working, I don't think 2 monitors will work either in macOS Big Sur Dev Beta 1.

Just my thoughts and my experience.

YMMV.
 
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jonasneve

macrumors newbie
Jun 25, 2020
3
0
Thanks #anshuvorty - I assume the support for MST will be the same regardless if its in a dock or direct, but I might be wrong. Fingers crossed they will add the support.
 
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ion.nistor

macrumors newbie
Jun 27, 2020
1
0
Same here - using an HP Thunderbolt Dock G2 - fairly ok device, but can only use one monitor (though it has two DP outputs).
Was actually wondering why they omitted this for such a long time, since, as I understand, it's really a driver (software) issue. Currently, again, as far as I understand, MST is supported, but only for one display (i.e. 5K in multiple streams).
 
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Ma2k5

macrumors 68020
Dec 21, 2012
2,495
2,463
London
I am hoping for the same thing. I have two Dell U2520D's 🖥 🖥 and what to run them on my MacBook Pro 💻 via a single USB-C and connect the two monitors via the DP output/input, works fine on PC, but MacOS won't connect the second monitor 🖥 ❌ 🖥 , so Im running them with two USB-C as of now. I really hope Apple opens it in Big Sur 🤞

If we could avoid emoji’s becoming a normal part of sentences, that would be great.
 
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kjvmartin

macrumors regular
Oct 11, 2016
209
212
Detroit
Has anyone tested if traditional MST daisy chaining is working in the beta?

Like 1 laptop, USB power/video, and a DisplayPort link to the 2nd monitor.
 
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sipjca

macrumors newbie
Aug 13, 2020
1
0
Tried this on MacOS 11 Beta 4, and no support for MST. Just get display mirroring.
 
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urbanmacUser

macrumors 6502
Sep 9, 2008
266
251
I've just run into this issue. The place I work for has an internal catalogue of approved suppliers and products so I bought 2x Lenovo P27H-20 screens only to realise they use DisplayPort to daisy-chain.

Tried on latest beta but not working so I have filed a feedback request to Apple but as this has not been supported for years I don't think there is much hope here.
 
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jonasneve

macrumors newbie
Jun 25, 2020
3
0
I've just run into this issue. The place I work for has an internal catalogue of approved suppliers and products so I bought 2x Lenovo P27H-20 screens only to realise they use DisplayPort to daisy-chain.

Tried on latest beta but not working so I have filed a feedback request to Apple but as this has not been supported for years I don't think there is much hope here.


I think you are right, I don't understand why Apple makes this limitation, it not like they have displays that are in direct competition at this price point. I used to run to Thunderbolt displays but needed better resolution so I got the two Dell displays on a single stand, they work great but I am forced to connect with two USB-C cables every day. ... Not the end of the world, but still just wired that Apple wont let the system daisy-chain :(
 
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urbanmacUser

macrumors 6502
Sep 9, 2008
266
251
It's annoying as I work for very large company that is very hot desk orientated and has used DisplayLink but is slowly removing all DisplayLink docks and drivers and moving to single USB-C cable on the desk that promises "one cable for, power, ethernet and screens" expect for us Mac users it does not, power and ethernet yes but not 2 screens. Even the cheap low-end basic Lenovo laptops we buy work with both screens but a 16" MBP i9 maxed out does not.
 
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Monotremata

macrumors regular
Apr 11, 2019
164
67
Ontario, CA
Good to know, this discussion came up at work today (I work for one of the big monitor making folks), and someone mentioned the Big Sur beta. I only have one monitor at home so I cant test it but, at least now I can update everybody it still doesn't work at this point heh.
 
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Wraithbone

macrumors newbie
Original poster
Apr 14, 2010
18
14
Thanks everyone for the replies. It seems my dream of a single dock for all is not coming to fruition this time. It's weird they refuse to support MST.
 
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vemac575

macrumors 6502
Feb 18, 2018
309
133
I use an OWC TB3 Dock and it fully extends one TB3 port to 2 monitors, independent of one another, on my 2016 MBP, on Catalina.

So why isn't this working for you guys?
 
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adib

macrumors 6502
Jun 11, 2010
393
265
Singapore
Also how about Wavlink's multi-display Thunderbolt adapters? Such as this Dual-HDMI one? Will that work?

I'm planning to have three monitor setups (two 4K and the built-in one) with my 2018 MBP and would like to minimize the number of ports used (ideally only one and power would be routed through that adapter). I'd like to know which adapters that would work.
 
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ght56

macrumors 6502a
Aug 31, 2020
807
762
I use an OWC TB3 Dock and it fully extends one TB3 port to 2 monitors, independent of one another, on my 2016 MBP, on Catalina.

So why isn't this working for you guys?

Looks like an awesome dock but it doesn't provide full power for the 16-inch.
 
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vemac575

macrumors 6502
Feb 18, 2018
309
133
Looks like an awesome dock but it doesn't provide full power for the 16-inch.

That’s what a lot of people say but I never have any issues having it docked in. It is always at 100% charged and I will be working for at least 12 hours. So although it’s not technically “full power”, it’s enough power.
 
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Wraithbone

macrumors newbie
Original poster
Apr 14, 2010
18
14
Hi. You misunderstand the problem. There are two methods for dual display. Windows docks use one called MST, while Mac specific docks has something else. I have a windows MST based dock, and macs could easily support this by providing software support as the hardware supports it. For some reason they never choose to implement the protocol. Therefore some docks work with windows and multiple screens, and the others only work with macs and multiple screens. If MST was supported all docks should work on anything. This restricts me from using the same dock for windows and Mac. And it’s just because of a software enabled protocol. Mind you, they all work with one screen. If two are connected, the external screens will just be mirrors of each other.
 
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adib

macrumors 6502
Jun 11, 2010
393
265
Singapore
Hi. You misunderstand the problem. There are two methods for dual display. Windows docks use one called MST, while Mac specific docks has something else. I have a windows MST based dock, and macs could easily support this by providing software support as the hardware supports it. For some reason they never choose to implement the protocol. Therefore some docks work with windows and multiple screens, and the others only work with macs and multiple screens. If MST was supported all docks should work on anything. This restricts me from using the same dock for windows and Mac. And it’s just because of a software enabled protocol. Mind you, they all work with one screen. If two are connected, the external screens will just be mirrors of each other.

And what would be "this other" protocol and how to properly decide whether to buy a given dongle/dock to support the "multiple independent displays" use case on macOS? Naming the protocol could be useful for searching an e-commerce catalog (namely the ones that are not Amazon).
 
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dsgfhjk

macrumors newbie
Nov 27, 2020
2
2
I tried it today on Big Sur with docking station Dell WD19TB - and it did NOT work.
Two external screens connected via DP are still mirrored. So definitely no MST support was added to Big Sur.
 
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MadsN95

macrumors newbie
Nov 30, 2020
1
1
You CAN run 2 external monitors over 1 cable from your mac.
To understand why, it's important to explain, that there are 2 different ways of getting your image out on the screens.

First thing is MST. A technology that allows daisy-chaining displayport signals. For this to work, the OS needs to support it. Windows does, most of the popular Linux distros does, but macOS does NOT.

Second thing is called Displayport Alternate Mode (we'll call it DAM from now on). DAM is a technology associated with USB, which is the part of the USB signal that carries the video signal.

SO, now that we understand the difference, let me explain how you can connect 2 external monitors to your mac, through one cable only.

If you hadn't already guessed, it requires a Thunderbolt3 dock. (A normal USB-C dock won't work)

A Thunderbolt3 dock (a good one is the CalDigit TS3 Plus), takes the Thunderbolt signal, splits of all the different signals it can transfer (video, ethernet, sound, USB data, etc.) and gives them a port for you to plug your stuff into. Like any other Dock. What makes Thunderbolt docks interesting, is that the Thunderbolt3 signal itself, is daisy-chainable. So in addition to get access to all these ports on the dock, it also comes with a Thunderbolt3 port, to allow further chaining of other devices. Here comes the clever part... Now you a Displayport signal (the one from the docks Displayport port) and another Thunderbolt signal.. both able to carry a video signal to a monitor! NO MST happening, as you "split" the Thunderbolt signal, and not the displayport signal.

So now, you connect one monitor to your Displayport port on the dock, and then you grab a USB-C to Displayport cable, and connect your second monitor to the Thunderbolt out on the dock.

And WOILA! You now have 2 independent external monitors connected to your mac, through only 1 cable.

In theory, you can keep adding more monitors (as long as you dont reach the Thunderbolt3 40GB/S bandwith limit), by daisy-chaining more docks together, and using their Displayport out, because you use the DAM technology in the Thunderbolt signal, instead of the MST.
 
Last edited:
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dsgfhjk

macrumors newbie
Nov 27, 2020
2
2
You CAN run 2 external monitors over 1 cable from your mac.
To understand why, it's important to explain, that there are 2 different ways of getting your image out on the screens.

(***)

So now, you connect one monitor to your Displayport port on the dock, and then you grab a USB-C to Displayport cable, and connect your second monitor to the Thunderbolt out on the dock.
Though I agree it works (Dell's suggestion agrees with yours) it is more of a workaround than of a viable solution.
I personally tried it but turned it down, and returned my Thunderbolt docking station. I reverted to using a DisplayLink docking station (which is no lesser ugly solution if you ask me). Shame of Apple to not support MST.
Apple-Dock1(1).jpg
 
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