MBPr 2015, 2.5GHz i7 – Daisychaining 2 Dell U2414H 61 Screens [duplicate]

Marking this question as an already existing question is wrong as the other question refers to a Mid 2012 NONretina Macbook running 10.10.1 instead of 10.10.3/4

I think that daisy chaining DisplayPort screens under OS X 10.10.4 is not possible, due to software limitations defined by Apple.

After Googling for some hours, spending 1.5 hours talking to the Apple Support and another hour talking to the Dell support, I don't know where else to find a solution than here.

This is my problem:

I just bought a new MacBook Pro Retina 2015 2.5GHz i7, 16GB RAM, NVIDIA GeForce 750M running OS X Yosemite 10.10.3.

I have two Dell U2414H 24" screens.

I want to use one of my two Thunderbolt/DisplayPort ports from my MacBook to connect both screens via a daisy chain. (I know that I could easily plug each screen into its own Thunderbolt/DisplayPort. But I need to use one Thunderbolt/DisplayPort for my Ethernet adapter, so I only have one left.)

So the setup I'm trying to run looks like the following:

MacBook --(from mDP to DP)--> Screen 1 --(from DP to mDP)--> Screen 2

However, whenever I connect the cables like this, I only receive the same image on both screens, i.e. the image is mirrored to both screens.

I don't understand why this is the case. If I connect the same setup to a Windows machine, it is working fine. While Googling I found some articles which say that "a Mac running Windows will daisy chain monitors".

Both screens support DisplayPort 1.2 as well as MST ("DisplayPort 1.2 added support for Multi-Stream Transport (MST), enabling multiple monitors to be used via a single DisplayPort connector.") and I enabled Display Port 1.2 on both screens within the menu.

So, as Windows machines and a MacBook running Windows support this setup, I concluded that it has something to do with OS X running. I tried to download the newest drivers for my graphic card form Nvidia. However, I learned that Apple provides the drivers, not Nvidia (“Nvidia drivers are provided by Apple and they are updated with every OS X maintenance update.”).

So I think that Apple is intentionally restricting the usage of Display Port 1.2 with non-Apple screens by limiting this function within the drivers.

Can this be true?

Does anybody have a solution for this problem, or know what to do?

I tried to find open source drivers for my graphic card and my MacBook which would enable this function, or maybe some hacked drivers, but had no luck yet.

Update 1: 3 June 2015

After Googling again for some hours, I decided to test the statement (link above) that a MacBook running Windows is able to daisychain. I installed Windows 8.1 on my MacBook via Bootcamp.

When running Windows 8.1 with the actual Nvidia drivers, daisychaining multiple displays through one Thunderbolt port is possible.

So I conclude that Apple is intentionally limiting the capabilities of OS X, to force customers to buy their Thunderbolt displays if they want functionality that should be possible with normal displays, and breaking the official standards.

I contacted the Apple Support again, and met a very competent and helpful supporter, who deep-dived into my problem. He escalated the problem to the European technology department of Apple, questioning why daisychaining display port monitors is not possible on OS X.

I am still waiting for a response from the department, but this can take up to 5 days, according to the supporter.

If I get any answer, I'll post it here.

Update 2: 6 June 2015

Today my Apple support rep gave me a call to inform me that he received a response from the European technology department of Apple. However, the department only referred to a support article of Apple and quoted the following "[...] as each Thunderbolt port can support one Mini DisplayPort display." Therefore, they could only speculate why daisychaining does not work but decided to not do so as it wouldn't help.

My support then told that this answer is not very satisfying and asked for further help.

It seems like this daisychaining problem is either not known at Apple and therefore not solved (maybe we can make Apple pay attention by spamming the developers with the form mentioned below), or Apple does not want to solve the problem in order to force customers to buy the more expensive Apple Thunderbolt Display.

I am keeping this thread up to date for other people searching the web for the same problem.

If you are experiencing the same problem, then please fill out Apple's feedback form and tell the developers to change the macOS behaviour regarding daisychaining.

Solution 1:

Apple does not support Display Port daisy chaining.

Using Thunderbolt screens, this would work, and because the Apple screen is a Thunderbolt screen, that works. The fact that Windows supports DP daisy chaining, does not mean that Apple does this intentionally to force users to buy their monitor.

So... Never attribute to malice that which is adequately explained by stupidity.

I wouldn't even call this stupidity, just ignorance, or the simple fact that nobody at Apple was aware of this situation and didn't test for it, or they did test for it and decided it wasn't worth the money.

Solution 2:

This is answered at Apple Macbook Dual Monitor MST already.

Apple is not "intentionally limiting" anything. They simply didn't add MST support to OS X because their hardware doesn't need it. The physical Mini DisplayPort connector on your Mac can operate in two modes, one is DisplayPort itself. In this mode, you can connect a single 4K 60 Hz monitor to your Mac. Or, you can use it in Thunderbolt mode where the displays use the Thunderbolt bus which has two DisplayPort signals multiplexed into the stream and each monitor gets one signal out -- but it's DP 1.1a so 4K 30 Hz or Full HD 60 Hz.