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Comment by mastax | Hacker News Reader

It's kind-of crazy that macOS still doesn't support DisplayPort Multi Stream Transport - the ability to drive multiple displays with a single DisplayPort cable. That kind of thing fits Apple's ethos very well, and they are heavily involved in the DisplayPort spec and support.

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My MacBook Pro (15-inch, 2017) has two 34UM88s chained on a single Thunderbolt port somehow.

That's TB daisy chaining, not DP's multi thing

Whoa, how?! Everything I’ve read indicates that Apple MacOS does not support TB (or was it USB-C?) daisy chaining

I have a USB C monitor and a second monitor connected to the first monitor with a DP cable. The USB C cable is connected to a ThinkPad x270 (a machine from 2017) running linux. Am I missing something regarding TB vs USB C + DP, or are you saying that this setup wouldn't work on a newly released MacBook? It sounds pretty unbelievable to me.

Yes. Apple doesn't support DP daisy chaining and they only recently added support for variable refresh rates on Macs despite it being a thing in the monitor space for 8 years. If their own products don't use it they don't care about it.

My theory is they want to you buy Thunderbolt displays. They get a cut of sales of Thunderbolt, but not a cut of DisplayPort, since it's a standard that is free of royalties. There's literally no other reason I can think of not to support MST out of the box on these laptops. Especially if they are involved in working on the spec.

Thunderbolt has been royalty-free since 2019, when it was licensed to the USB-IF to be used as the basis for USB4.

https://arstechnica.com/gadgets/2019/03/thunderbolt-3-become...

(I also suspect that Apple's cut wasn't huge to start with; Thunderbolt was developed with Intel, and Intel likely got the lion's share of royalties given that they were the ones actually selling the Thunderbolt controllers and seem to have been the driving force behind Thunderbolt 3.)

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