Apple limits daisychaining of non-Apple displays in OS X | Hacker News Reader

Apple limits daisychaining of non-Apple displays in OS X

apple.stackexchange.com

81 pointscodezombie55 comments

This is pretty simple. Apple does not, and never did, support DisplayPort daisy chaining.

The confusion lies in the fact that Apple does support Thunderbolt monitor daisy chaining, and Thunderbolt uses the same port as mini-DisplayPort.

That the hardware can support it is irrelevant. Apple hardware can do lots of things that Apple doesn't support or claim their hardware can do.

Call it malevance on Apple's part if you want, but it's really just them choosing to only support some things, not all the things.

This is the correct answer. You can't blame Apple for not supporting a feature they never claimed to support. I don't think there's malicious intent here, rather a lack of demand or awareness.

It's purely lack of demand. You can use dual monitors by either (a) using both MiniDP ports, (b) using one HDMI/MiniDP, (c) using USB/MiniDP. But the OP wants none of those.

I can easilty blame Apple for locking out functionality that underlying hardware supports though. Especially when it's essentially functionality handled by the hardware layer and drivers not written by Apple at all.

There's a big difference between "locking out support" and "not doing extra work to support a feature we don't need."

Should I blame Microsoft for not supplying all software ever written with Windows? After all, my PC is just a Turing machine, so by not providing me with all the software ever written, they're locking out functionality the underlying hardware supports.

The actual big thing about Turing Machines is that they can simulate “nicer” Turing Machines. So, a better analogy would be a company that doesn't support (or even expressly forbids) running certain kinds of Turing Machines on the Turing Machine that they sold you.

Consider that an Operating System is just a simulation of a nicer Turing Machine than the hard-wired Turing Machine on which it runs. Similarly, an “interpreter” is just a nicer Turing Machine that is being simulated on top of an OS.

So, for a complete analogy, we’d need a company that either restricts what kind of OS that you can run on the hardware that they sold you, or that restricts what kind of interpreters you can run on the OS that they licensed you.

I'm confused though. If they support MST[0], how did they rip out daisychaining specifically? I don't understand MST well enough to see how a computer connected to one large monitor with two MST regions would be different than two monitors daisy chained using MST.

It really does look like Apple specifically has disabled it because there isn't an apple product that supports it, but that may be due to my own ignorance of MST.

[0]: https://support.apple.com/en-us/HT202856

Apple has the right to claim that using unsupported hardware is...well....unsupported. However, it sounds like they nerfed the driver which makes it a non standards complaint driver. This is a problem and Apple needs to be called out on it. At the very least, they could face sanctions or a trademark lawsuit from the display port standards group for using the logo with non compliant products. At the worst, a hefty fine from the EU.

Also, there's no point in "flooding" developers with support requests. Devs will rarely read what customers write anyways in large corporations like Apple. Better to push from the standards org or the govt regulator.

They're compliant with DP 1.1. The DP association doesn't require 1.2 be supported, although Apple really ought to. There's really not that much substance to the OP's hand waving here except for the fact that it's disappointing that there is driver support for the same hardware in Windows.

This isn't quite accurate. As far as I'm aware, Apple has never supported display port chaining (MST I think?).

I'm pretty sure the reason Apple's display works is that it's a Thunderbolt Display and not a DisplayPort display.

It would be good to have this support available, but describing it as an intentional software limit is disingenuous.

"This question has been asked before and already has an answer."

This is the single MOST ANNOYING thing about stack exchange. WHERE was this question asked before? How about a link to the original question? Hello?

To be fair to Stack Exchange, that's a behavior that's been around forever; at least since USENET. It is very annoying, though.

"How do I do this?"

"USE THE SEARCH, NOOB"

(Search results contain dozens of people asking the same question; not a single answer; and then someone saying "never mind, fixed it" with nothing about what they did to fix it)

The yellow box above the question does give a link to the previous answer. Is that what you're talking about?

EDIT: also, more annoying is-

"I want to do this. How do it do it?"

"No, don't do that. Do this other thing instead."

Why is that more annoying? Do you really expect people to give out what they themselves believe to be bad advice, and is so, is that really desirable?

It's preferable to just ignore the question; or to ask in comments if alternative solutions are wanted.

The worst is when you ask something that is subtly different enough that it really isn't the same question anymore, and then they shut you down anyway. Perhaps to somebody with expert-level knowledge, it might be the same, but for someone trying to learn something new, subtle differences can be huge.

It irritates me when they flag the question as duplicate and not provide a link to the possible original and it's incredibly hard to find a similar question. It wud be just easier to link the original instead of all the traffic coming from google finding a dead end.

It's impossible to do that on SE sites - if you try to flag as a duplicate, the site requires you to chose the question you believe the one you are flagging to be a duplicate of. The ability to vote is disabled until you do, and the site then shows the link in a comment and eventually at the top of the post if it gets closed.

Good news - it's literally right there at the top of the question. "This question already has an answer here:" with a link. It is impossible to close a question on SE sites as a duplicate without providing the question being duplicated, for this very reason.

I'm not sure why this hit the front page of HN this way.

Thunderbolt does not implement MST chaining (because it conflicts with Thunderbolt chaining; someone out there is going to try to chain a Thunderbolt device into a Displayport device and wonder why Thunderbolt functionality doesn't work but the display part does, essentially. Apple doesn't want to deal with this shit.)

However, the last device in a Thunderbolt chain can be a standard non-MST Displayport monitor, this IS supported afaik.

The thunderbolt monitor isn't 5 times more expensive, it is 3 times more expensive. It also has many features your displayport monitor does not have. It has a thunderbolt hub w/ a thunderbolt port. Apple is daisy chaining their displays over thunderbolt. It also contains a gigabit ethernet adaptor, usbs, and a video camera.

My primary point is that they don't support displayport daisy chaining with their displays. They support thunderbolt daisy chaining.

It's also a 2560x1440 screen sold for $999. An upgrade with their latest 5K display is overdue.

I just recently bought a couple of Dell U2515H monitors (and will probably buy another), and, given you can buy three of them for the cost of one of Apple's Thunderbolt displays, they really are a great deal - same resolution, higher PPI, more adjustable and rotatable, and they're matte.

My Apple Thunderbolt display has from day one had some light leakage in the lower right corner, and the ethernet port stopped working six months ago, but I'd always convinced myself it was worth the extra money over a Dell or equivalent. I'm now pretty sure it never really was apart from a brief period when they were about the only 2560x1440 displays you could get.

I hate to say this, but the U2414H is a better monitor. Zero processing latency (not 1 frame, not half of a frame, but real world measured latency of less than 1 ms; virtually all of the gamer monitors out there are at least 1 frame and the only ones that get <half a frame are those Korean single input scaler-less IPSes), often sold for below $250 each, excellent color and contrast.

I have three on my desk.

It's 1920x1080, though, right? The U2515H is 2560x1440. That difference is far more important to me than a few milliseconds of latency (I don't play games).

Yes, but they're also often for sale for around $250. I bought three.

I got an U2515H at work last week (for use with my MBP) and am amazed at the effect it's had on my working patterns in such a short space of time. Simply being able to have documentation, browser and editor open at once and not feel 'cramped' is amazing.

I don't see why this user shouldn't be frustrated, though. It is still an OS-specific limitation, since it appears that Windows will run them in a manner acceptable to the user.

OS X generally has terrible 3D support and the same hardware on Windows will perform much better. That's unfortunate but no reason to go to court for.

Apple writes their own device drivers and they write them to the extend their software and hardware needs it and no step further.

It seems to be intentional though. I seem to recall Microsoft and IBM got into big trouble for anti-competitive conduct. This is the sort of thing that brings about anti-trust suits.

1) It's not intentional though.

2) Apple doesn't prevent you using dual monitors via other means e.g. USB / HDMI.

3) Microsoft/IBM had ridiculously high market shares (>90%). OSX is around 10%.

Anti-trust on their whopping < 8% marketshare? You'd get laughed out of court.

All this because osx doesn't do a thing that apple never claimed osx did.

http://en.wikipedia.org/wiki/Usage_share_of_operating_system...

It seems intentional in a "it would cost resources to extend this past what we benefit" way. In other words, a business made a cost-benefit analysis.

I fail to see where your frustration is coming from, or why it's targeted at Apple. It's most likely just a calculated cost savings measure.

The frustration is targeted at Apple, because someone there likely made this decision... The support was likely already written, and expressly removed, because Apple makes Thunderbolt monitors. Not to mention that Apple is known for it's wide profit margin, so any cost/benefit analysis is less meaningful in that regard.

I'm not sure where you think said frustration should be directed.

Rather than speculating on what Apple did internally, I think the real question is whether Apple advertises DisplayPort 1.2 support, since this feature is part of the DP 1.2 spec. So far I can't find anything about this on their product pages. If that's the case it's basically users demanding features that were never put into the specs of a product.

Then Apple is in trouble:

Mini DisplayPort Connector

The Mini DisplayPort Connector is a small form factor connector designed to fully support the VESA DisplayPort protocol. It is particularly useful on systems where space is at a premium, such as portable computers or to support multiple connectors on reduced height add-in cards.

https://developer.apple.com/softwarelicensing/agreements/min...

It doesn't say which version though.

Mini DisplayPort started from 1.2 of the DisplayPort standard.

I agree with some frustration, but getting upset that apples aren't oranges isn't valid.

Someone would need to write the driver for this functionality. I expect Intel is happy letting apple do the work, but so long as that is the case, Apple has no need to support every hardware and protocol under the sun. They merely have to support their stuff fully, and beyond that it is someone else's problem.

Intel wrote the driver for windows, and it works on Windows. That's also apples and oranges IMO.

Limits? AFAIK Apple doesn't support daisychaining via Displayport at all. Just Thunderbolt.

There are no Apple displays that support daisychaining via Displayport either, so this whole notion that Apple actively sabotages 3rd party DP displays is nonsense.

Now, one might argue that you would want them support this because it's technically feasible with the current hardware (I have no idea), but there might be a ton of reasons why Apple doesn't.

AFAIK, such displays weren't even available when this generation of Macbooks were built, so the most likely explanation is the Apple simply didn't bother initially and until very recently had no reason to revisit that decision.

I'm not a huge fan of Apple, but I have to agree with you. Windows doesn't (yet[1]) have a built-in SSH client or server, even though OS X and Linux do. Should I sue Microsoft because it doesn't do one specific thing in software, even though the hardware allows it if I install another OS?

[1] http://arstechnica.com/information-technology/2015/06/micros...

When any end user can easily add the functionality you are referring to, for free, to an operating system you can buy, pre-installed on a 7" tablet with an SSD, Quadcore x86 CPU and HDMI out, for less than £70... I think you might be making a flawed comparison.

How exactly does one freely and easily add (reasonably expected) functionality to OS X? Due to how much escalation was required, even Apple themselves thought it should work.

As the article stated, you can make the hardware do what you want to by changing the software (OS X to Windows or Linux); in other words, the hardware isn't the limitation, only the software. In my example, your computer's hardware is fully capable of being used for SSH, you just have to use the right software.

My point being, unless Apple sabotaged the hardware to make it only usable with their brand of displays, there's really no harm done here. You don't buy a 4K TV, hook it up to a 2005 era DVD player, and expect to see 4K resolution on the screen just because your TV had a plug that accepted the DVD player's cable. Just because the plug fits doesn't mean the capability is there. If you want MST over DP, use the software that allows for it, and if that means installing another OS, then so be it. Petition Apple to allow MST over DP as well as Thunderbolt and explain to them that they lost a Mac user to Windows or Linux because of this.

I hope that makes it easier to understand.

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.

Your four responses on the stackexchange question and here really convinced me. There is just no way that Apple would ever limit the customer's choice by doing (or not doing) something! Apple's intentions are always pure and I know this because... reasons.

It's kind of like the App Store (on iOS) - they are not intentionally limiting you to one app store, they just didn't add support for other company's app stores.

Apple is not limiting customer choice. They ship the MBP with 2 x mini DP so you can use dual monitors.

And nothing is stopping anyone running their own App Store on OSX. Mac Update has a sort of one already.

Uh don't take me for an Apple apologist ... I am well aware and often advocate of how their business model leads to unfortunately limiting everyone's freedoms. But this one is not one of those, I think.

You shouldn't have bought a Mac in the first place, of course but that cause is seemingly lost. People are not listening to Cory Doctorow so why would they listen to me?

When you plug in one of those 4K 60 Hz monitors, you're probably using MST - most of them are designed to appear to the host PC as two separate monitors daisychained over DisplayPort MST, with some extra metadata to tell the OS they're actually two halves of the same monitor, and OS X supports this on newer hardware. Which means Mac OS X has code somewhere to detect if you're trying to actually daisychain non-Apple monitors and disable MST.

As outlined in comment, Dell specifically refused to provide support for Apple OS X. I don't understand the reasoning to use proprietary system (which you can't modify) with unsupported hardware. It's not obvious who to blame in this situation. Apple is not obligated to provide support for every equipment combination out of there. Buy supported hardware or use Windows or use free operating system and write drivers for your hardware.

If writing drivers for arbitrary hardware were remotely viable I would be the happiest clam in the ocean.

I really hope Apple reads that feedback form. Safari on iOS has a broken Content Security Policy for the font-src (namely 'self' isn't working) and I am getting flooded with false reports.

When I google it I only find an unanswered post on Stackoverflow: http://stackoverflow.com/questions/29417735/content-security...

Do so few people use content security policy? How did this go unnoticed for so long?

If you want Apple to fix issues report them through Radar: http://bugreporter.apple.com

They do get triaged by the engineering teams.

http://multimonitorcomputer.com/solved/dell-u2414h-displaypo... ?

I own three U2414Hs. This is clearly outlined in the manual and also on the quick start sheet that was in the top of the box when you opened it.

I've tested it, it works fine.

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