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by lathiat 969 days ago
I really, really wish they would fix this silly display scan-out limitation. I gave them a (frustrating) pass on the M1 given it was the first evolution from iPhone/iPad where it wouldn't have mattered. But seems silly to have made it all the way to the M3. Wanting to dock onto two displays even at the low end doesn't seem like such a niche use-case.

I'm sure there is some kind of technical explanation but both Intel and NVIDIA seemed to managed 3+ scanouts even on low end parts for a long time.

4 comments

The technical explanation is that on the base M1/M2 SoC there is one Thunderbolt bus that supports 2 display outputs.

On the MacBook Air one output is connected to the internal display leaving one output for an external display.

(The Mac Mini that uses the same SoC is limited to 2 external displays for the same reason)

To support more displays they would have to add support for a second Thunderbolt bus to the base SoC.

Is this an actual hardware issue though? One issue is MacOS has never supported DisplayPort MST (Multi-Stream Transport) EVER as far as I can tell. MST allows for multiple display streams to be natively sent over a single connection for docks or daisy chaining monitors. Back on Intel Mac's if you had a dock with 2 displays or daisy chained 2 together you would get mirrored displays. The exact same Mac/displays in boot camp MST would work perfectly. 1x display per Thunderbolt 4 port is the worst!
You can get multiple displays from a single port, the hubs are just expensive.
You can't do it with a base model M chip. Not supported on Mac unless you go with displaylink and displaylink has weird issues on mac like no hdcp support and screen recording enabled that make it a really bad experience compared to mac.
There's no reason a whole Thunderbolt bus is needed for every two displays. It's just Apple's decision to build their GPU that way.

And to not support industry standard NVIDIA GPU on ARM Macs, too. 1 GPU typically supports 5 output over as little bandwidth as PCIe x1.

Not with nVidia, no, they are 4 displays, always has been. The NVS810 8x display card is using two GM107 GPUs.

AMD is 6 displays. You see this rarely on consumer boards but the ASRock 5700 XT Taichi for some inexplicable reason did expose all six -- with four DisplayPorts to boot, too. I do not think there has been 4 DP or six output customer cards since.

Even with less ports you can use Display MST hubs to breakout 3 displays from one. (But not on a Mac, even intel, they never added driver support. Works in windows boot camp though)
There are couple 900-, 10-, 20-, 30-Series NVIDIA with 5 outputs. 700- and below had up to 4. IIUC it's more like up to (x px, y px) max with up to N independent clocks without external adapters or something along that.
Just because there are X outputs on GPU, doesn't mean it will work with all of them at the same time
I was doing 5 for no reason from a GTX970 at one point. They just work. But for some reason(segmentation?) NVIDIA brochure pages sometimes disagree or contradict with products in the market.
Right, but why can't you disable the internal display to run 2 external displays? That wouldn't be an unreasonble compromise but seems not possible.
M1/M2 only has 1 native HDMI pixel pipe in any form, I think? Apple uses the HDMI PHY to drive the screen on tablets, and the screen on laptops. Base-tier M1/M2 also only have a single displayport pixel pipe, and Pro/Max get +1/+2 respectively.

The base-tier chips are designed as high-volume tablet chips first and foremost, with ultramobility crossover capability.

Using DisplayLink or certain kinds of thunderbolt multimonitor are possible while running outside the pixel pipe or running multiple monitors on a single pixel pipe (this is not MST which is multiple pixel pipes on a single stream). But yeah it's ugly especially on a base-tier processor with this eating cycles/dumping heat. You're running the hardware encoder at least.

Discord had this weird error if you tried to enable the screen/audio capture, it tries to launch something and fails and the solution is you need to manually install "airfoil" because it's an audio capture module that discord licensed. you don't have to fully install it but the audio driver is the part that discord uses and that goes first (has to be allowed as a kext, ie non-secure mode). theoretically a kernel-level capture like that could be a ton faster than userland, I think that's the on-label use of airfoil.

Allow the user to turn off the internal display in favor of 2 external displays. That would be a usable docked configuration.
you are right, but apple won't do this.
independent repair technician demo video to mux MBA internal and external display?
>I'm sure there is some kind of technical explanation

I'm sure it's a marketing explanation: they make bigger margins on more expensive machines, and they need some feature differentiators to nudge people to move up. 2 extra displays is a poweruser/pro feature.

They make their own silicon, it's not like they're shy about designing hardware, if they wanted to stuff features into the lower end books they easily could.

> Wanting to dock onto two displays even at the low end doesn't seem like such a niche use-case.

I mean, it almost certainly is? I would guess a majority of the low-end SKUs are rarely if ever attached to one external display. Two would be rarer still.

At a ~recent work place the entire floor of developers had (Intel) MacBook Pros with dual 24" monitors.

Some of them were trying out Apple Silicon replacements, though I'm not aware of what they did monitor wise. Probably used the excuse to buy a single large ultrawide each instead, though I don't actually know. ;)

Which workplaces are these that buy low-end laptops for their employees but shell out for dual monitor workstations?
Is a 1,599 laptop a low-end laptop? An M3 Macbook Pro 14" that costs $1,599 can only drive a single external monitor according to the spec. A $1,000 Dell XPS 13 can drive 4 monitors via a single Thunderbolt 4 Dock that also charges the laptop!

Honestly, I'm an accountant and everyone in my office uses 2-3 monitors with $1,200 business ultrabook.

I think this use case is probably not the majority.
So? Intel doesn’t seem have any issues supporting it regardless of that.
External displays can be used for multiple generations of laptop hardware. Unlike CPUs, displays are not improving dramatically each year.

MacBook Air is a world-leading form factor for travel, it's not "low-end".

MBA with extra storage/RAM can exceed revenue of base MBP.

We’re still talking the low end of this product line. If you’re buying two monitors for your employees, I’m not sure you’re skimping on the cost between an M3 and an M3 Pro.
As stated, it's not about cost.

The travel form factor of MBA is not available for MBP, for any price.

What's Apple high end laptop product line?
> low-end laptops

Heh, that's not how I would describe MacBook Pros. ;)

I work at Motorola and we get M1 airs unless you specifically request a Linux laptop. I wouldn't call it low end though. Low end is an Intel i3.
> low-end laptops

you're saying they're low-end because Intel? if you've got your macbook connected to two monitors, you're not very concerned about battery performance.

So isn't Intel silicon competitive speedwise? I thought the M[0-4]s were OK but sort of hypey as to being better in all regards.

I have worked in plenty i5-i7 windows/linux laptops before and a macbook m1 air with 16gb of ram is miles better in everything. Nothing like them.

And even if you do not care about battery, you still care about throttling.

Honestly anyone who calls them hypey hasn’t actually used them and spends too much time arguing about geekbench on forums.

Real world, the M series chips are by far the best I’ve ever used as a software engineer and it’s not even close.

Not a chance. Moving from an Intel MacBook Pro to an Apple Silicon MacBook Pro was absolutely revolutionary for me and my very pedestrian ‘interpreted language in Docker web developer’ workloads.

I’d seriously consider not taking a job if they were still on Intel MacBooks. I appreciate that an arch switch isn’t a piece of cake for many many workloads, and it isn’t just a sign of employers cheaping out. But for me it’s just been such a significant improvement.

More like cheap out on monitors such that devs want two crappy monitors instead of one crappy monitor
What dev shop gives their engineers base model machines?
Doesn't need to be a dev shop. Go into any standard office and most productivity office workers will be running dual monitors now.

But with the general power of the base model Apple Silicon I don't think most dev shops really need the higher end models, honestly.

Where are you getting that impression from the parent post? Maybe they were on a 2, 3, or 4 year upgrade cycle and still had a bunch of Intel MBPs when Apple Silicon hit the market. That'd be extremely typical.

What dev shop immediately buys all developers the newest and shiniest thing as soon as its released without trialing it first?

We stuck with Intel MBPs for awhile because people needed machines, but the scientific computing infrastructure for Apple silicon took more than a little bit to get going.
Yeah, they were running Intel Macbook Pros because that's what everyone was used to, and also because production ran on x86_64 architecture.

At least at the time, things worked a bit easier having the entire pipeline (dev -> prod) use a single architecture.

Yeah, that was my experience. The early M1 adopters at my previous company definitely ran into some growing pains with package availability, etc.

(Overall the transition was super smooth, but it wasn't instant or without bumps)

Huh? He was talking about dual monitor situations being a problem.

If the company bought Pro or Max chips and not base models, it wouldn’t be a problem.

Intel has supported three external displays on integrated graphics since Ivy Bridge in 2012.
I’m not sure what that has to do with it being a niche use-case or not.
Niche or not, being more than a decade behind the competition is gauche.
On one somewhat niche feature, on the lowest SKU in that particular product lineup.

I can pick areas where Apple is beating Intel. Different products have different feature matrices, news at 11.

They also don’t show any signs of catching up to the Raspberry Pi’s on GPIO capabilities.
They did with https://ark.intel.com/content/www/us/en/ark/products/series/... but sadly seem to have killed off that product line.
Apple does not compete on checkboxes. If they deemed is necessary to remove, there’s a reason. Not saying I agree, just that’s how they operate. If there isn’t a need to support 3 displays then they won’t, regardless if the “competition” did it years prior.
> there’s a reason. Not saying I agree, just that’s how they operate.

Almost always it’s maximizing profit margins rather than anything else.

>there’s a reason

they operate 100% on profitability, not what's technically feasible. They are extremely focused on making money. Yes, there is a reason after all.

If that were true Apple would have stopped bragging about battery life.
It has nothing to do with niche use-case or not. This is a regression compared to their own Intel Macbooks.
Well the number with two screens would be zero, because you can't do it. That doesn't mean people don't want to do it because 0% of the laptops do it. They're just unable to.
It’s a bit funny though that their competitors don’t seem to have any issues supporting this on pretty much all of their products.
Display pipelines are expensive and take area.
Easy to say but hard to prove. How much more expensive would an MBP be if they supported it? How many fewer units would they shift?

Those are harder questions to answer. We could assume Apple crunched the numbers. Or perhaps they just stuck to the status quo.

Only an insider or decision maker (maybe that’s you) knows.

The CEO is a supply chain guy. They've been optimizing their profit margins ruthlessly since he took the helm. I don't think any savings are too small, particularly if comparatively few users are affected and it motivates upselling.

I think it's weird though how far people go to defend Apple. It's objectively making (some) users worse off. Apple clearly doesn't care and the people defending them also clearly don't. But the affected users do care and "but money" isn't really a good excuse for them. It also doesn't solve their problem of not being able to use two external monitors anymore without spending significantly more money.

I think their assumption is that if you’re the kind of pro that needs that many monitors, you’ll upgrade to the better chips they sell.

But it’s a frustrating limitation and remains one of the only areas their old intel based laptops were better at.

For the past 3 years, including with the latest laptops, "better chip" means 14" M* Pro starting at $1,999. $1,299 M1/M2 or $1,599 Macbook Pro does not support that. When you can find support for dual external display on $600 Windows laptops, or Intel Macbooks since at least 2012. By any standard this is an embarrassment and a regression.
Having 2 monitors isn’t even that ‘pro’ these days. I see receptionists with three sometimes.
An assumption they are so unsure about, that they kind of force that decision on their users.
It’s a money thing. Apple wants to upsell. The production cost would be negligible, but now you have to buy the next level of the product.
I mean they are physical things and you can look at how big they are. But sure the rest of how that factors into cost and sales is harder to figure out, yes.
Unless you’re Intel?