External monitor support

[joevt]

The last-gen Intel Air, with its two TB ports, could drive two monitors. But the M1 Air, which also has two TB ports, can't. I'd be interested to know the technological reason for the difference.

Possible reason: M1 is a iPad processor. iPad only supports its display and one external display. Therefore, the M1 Air supports its display and one external display.

From https://en.wikipedia.org/wiki/MacBook_Air :

Last-gen Intel Air
2× Thunderbolt 3 (USB-C 3.1 Gen 2) ports supporting charging and DisplayPort
Supports two 4096x2304 displays or one 6016x3384 (MST) display

Current M1 Air
2× Thunderbolt 3 (USB-C 4) ports supporting charging and DisplayPort
Supports one display up to 6016x3384 (MST)

That's wrong. The Apple Pro Display XDR does not use MST for 6K. It uses DSC. Or it can use two DisplayPort signals over Thunderbolt which is called dual SST, not MST - but the M1 doesn't have two DisplayPort signals for Thunderbolt, which is why it must use DSC.

It's likely possible that the M1 does not support MST even for old 4K displays (the first 4K displays used MST to achieve 4K resolution - this uses two streams of 1920x2160 over DisplayPort).
macOS supports MST for old 4K displays but does not support MST for multiple displays.

Following - have dual 1080P USB-C monitors I use via a thunderbolt dock for work (Windows laptop), would love to be able to connect the Air to it as well...

Seems silly it can drive a 6k monitor but not dual....

Two bad there aren't any non-MST DisplayPort video wall processors/splitters/matrix switchers/video wall controllers/signal switches.
Or if there are, they are probable very expensive. I would want want that does DSC to allow connecting multiple 4K displays.
For dual 1080p a 4K HDMI video wall processor would work (still expensive though at $200-300, plus you would need HDMI to DisplayPort adapters and DisplayPort to USB-C cables if your USB-C displays don't have HDMI inputs).

Maybe DisplayLink will work on M1 Macs. It's USB. Probably doesn't require a kext. So the drivers may work via Rosetta 2.

CORRECTION: M1 Macs have two DisplayPort connections to Thunderbolt, which can be used to provide full resolution on a tiled display like the LG UltraFine 5K, Dell UP2715K, or HP Z27q. But the two DisplayPort connections cannot be used to connect two separate displays. Whether a display is tiled or not, only one can be connected via Thunderbolt. This has been tested with a HP Z27q that can show the input resolution in its on screen menu. ioreg output confirms this for the LG UltraFine 5K. ioreg also confirms DSC for the 6K case.

 

[4sallypat]

I have been told I can use my 2009 late 27 inch iMac as target monitor for a Mac mini. Might seem like a strange thing to do but I’m trying to upgrade on a budget.. will this work? Thunderbolt to DisplayPort mini??

Yes you can use it as a target mode display for the M1.

I use a 2011 27" Apple Thunderbolt display on my 16" MBP so yes, your M1 will work with the adapter dongle.

Make sure you get the Apple branded TB3-TB2 adapter - don't get an aftermarket/knockoff....

 

[joevt]

I think this is unlikely to be true. Apple specifically calls out the M1 machines as able to support a single 6K monitor.

LG UltraFine 5K uses two DisplayPort 1.2 HBR2 signals over Thunderbolt 3 to achieve 5K. Each signal is 2560x2880. Apple calls this dual link SST.
Apple Pro Display XDR can do 6K in two different ways:
- two DisplayPort 1.4 HBR3 signals over Thunderbolt 3. Each signal is 3008x3384.
- one DisplayPort 1.4 HBR2 with DSC signal over Thunderbolt 3 or DisplayPort.

Since the M1 Macs only have one DisplayPort connection to Thunderbolt, it must use the HBR2 with DSC for 6K, and the 5K only has one DisplayPort connection so it will be limited to 4K.

Is there a way to connect 2 (TWO) 27" Apple Thunderbolt displays AND a small (12"x 5") HDMI display to the new Mac Minis....M1 or Intel?

You can only connect two displays to the M1 Mac mini, one via USB-C/Thunderbolt, and one via HDMI 2.0 port.
The Intel Mac mini supports three displays, two via USB-C/Thunderbolt, and one via HDMI 2.0 port.

From the Apple site foot notes.

If the Mac Mini M1 was tested with LG 5K then it should work.

The LG 5K can work but only at 4K because the Mac mini M1 only has one DisplayPort connection via a Thunderbolt port.

CORRECTION: M1 Macs have two DisplayPort connections to Thunderbolt, which can be used to provide full resolution on a tiled display like the LG UltraFine 5K, Dell UP2715K, or HP Z27q. But the two DisplayPort connections cannot be used to connect two separate displays. Whether a display is tiled or not, only one can be connected via Thunderbolt. This has been tested with a HP Z27q that can show the input resolution in its on screen menu. ioreg output confirms this for the LG UltraFine 5K. ioreg also confirms DSC for the 6K case.

 

[jazz1]

I’ve got a silly question. Does using two monitors in the M1 MacMini “tax”/impede performance?

 

[IgorK]

Techcrunch (very vaguely) seems to imply that M1 Macbook Pro does support two external monitors. Their wording is a bit strange though:

"The M1 MacBook Pro has two Thunderbolt controllers, one for each port. This means that you’re going to get full PCIe 3.0 x4 speeds out of each and that it seems very likely that Apple could include up to 4 ports in the future without much change in architecture.

This configuration also means that you can easily power an Apple Pro Display XDR and another monitor besides. I was unable to test two Apple Pro Display XDR monitors side-by-side."

 

[fishkorp]

The only thing stopping me from the switch right now is that I have 2 UltraFine 5K screens (original version). It’s a huge step backward for my work setup if I can’t use both

Based on all info so far, I really don’t think I’ll need a higher end model. But, sadly, it’s looking like I’ll have to pay a premium to drive my 2 displays.

I thought about selling them and getting something else, but once you’re used to these, it’s REALLY hard to use something else. Really, really hard.

 

[dl4ste]

can somebody test if it is possible to use 2 external displays on the new MBP M1 if the macbook is closed?

 

[Lammers]

Yes you can use it as a target mode display for the M1.

I use a 2011 27" Apple Thunderbolt display on my 16" MBP so yes, your M1 will work with the adapter dongle.

Make sure you get the Apple branded TB3-TB2 adapter - don't get an aftermarket/knockoff....

Not quite right. The 2009 iMacs are pre-Thunderbolt, so Target Display Mode uses DisplayPort, not Thunderbolt. So the connection required is USB-C to Mini-DisplayPort. The TB adapter won't work unfortunately.

 

[Lammers]

The only thing stopping me from the switch right now is that I have 2 UltraFine 5K screens (original version). It’s a huge step backward for my work setup if I can’t use both

Based on all info so far, I really don’t think I’ll need a higher end model. But, sadly, it’s looking like I’ll have to pay a premium to drive my 2 displays.

I thought about selling them and getting something else, but once you’re used to these, it’s REALLY hard to use something else. Really, really hard.

I think that has been the case for a while though - typically only the higher-end MacBook Pros have been able to drive two LG 5Ks. I use a 15" MacBook Pro (2018 I think) for exactly that purpose, even though I'd have preferred the 13" for portability when away from the desk.

 

[IgorK]

But then the Verge's review states flat out that "Only one external display is supported".

 

[DenBeke]

But then the Verge's review states flat out that "Only one external display is supported".

Could be that they just copied it from Apple spec page.

I'm really interested in seeing someone test this. My M1 MBA isn't arriving until next week, so I can't test it yet.

 

[fishkorp]

I think that has been the case for a while though - typically only the higher-end MacBook Pros have been able to drive two LG 5Ks. I use a 15" MacBook Pro (2018 I think) for exactly that purpose, even though I'd have preferred the 13" for portability when away from the desk.

I know. I was really hoping they’d change that. Guess that’s too much to ask.

 

[dogslobber]

But then the Verge's review states flat out that "Only one external display is supported".

They're non-technical. Somebody should actually try two LCDs.

 

[fishkorp]

Now I’m curious if something like a CalDigit TS3+ will allow for 2 displays on an Air? I know it won’t work in my case (2 UltraFine 5Ks), but maybe for other folks. I hope someone gives it a try.

never mind, found my own answer:
All of CalDigit’s docks are fully compatible with the new M1-based Macs including the ability to charge a laptop and more. However, the only limitation is that the new M1-based Macs cannot support dual “Extended” displays through their Thunderbolt 3 ports. This means that when using any dock, users cannot extend their desktop over two displays, and will be limited to either dual “Mirrored” displays or 1 external display depending on the dock.

im still curious if in clamshell that’s 1 “mirrored” plus 1 extended?

 

[navgs400]

I'm wondering this myself... my MBP is out for delivery so I'll post the answer if nobody else has by then. Two external monitors, will try clamshell shut, etc.

 

[deeddawg]

Now I’m curious if something like a CalDigit TS3+ will allow for 2 displays on an Air? I know it won’t work in my case (2 UltraFine 5Ks), but maybe for other folks. I hope someone gives it a try.

never mind, found my own answer:
All of CalDigit’s docks are fully compatible with the new M1-based Macs including the ability to charge a laptop and more. However, the only limitation is that the new M1-based Macs cannot support dual “Extended” displays through their Thunderbolt 3 ports. This means that when using any dock, users cannot extend their desktop over two displays, and will be limited to either dual “Mirrored” displays or 1 external display depending on the dock.

im still curious if in clamshell that’s 1 “mirrored” plus 1 extended?

My M1 MBA is due in a couple weeks and I'll have a chance to try it with my TS3+.

When I asked Caldigit about dual externals in clamshell mode though, they said not gonna work. Maybe they'd misunderstood my question, but I'm gonna guess probably not.

 

[saulinpa]

Just tried it on a M1 MBA. Only one external display at a time will work. Does show two separate TB buses though.

 

[Diode]

Just tried it on a M1 MBA. Only one external display at a time will work. Does show two separate TB buses though.

What was the setup? One monitor into each port? Using a dock?

 

[Bennett_H]

Just plugged in my new mbp with m1 in my lg 49wl95c-w with usb c. Max resolution I can get is 3840x1080...!

I have also the latest intel mbp here and it works just fine in 5120x1440!

Anyone with the same problem? I know there is "always" a problem with apple and ultrawide. The old MacBook (2017) by my girlfriend also only works in 3840x1080. But I really thought the new mbp m1 which I able to run 6k 60hz should be able to run 5120x1440 (which is less than 4k!)

 

[saulinpa]

What was the setup? One monitor into each port? Using a dock?

One monitor in each port. First with two LG 5Ks. Then tried using two adapters (DP and DVI) to two traditional monitors.

 

[navgs400]

One monitor in each port. First with two LG 5Ks. Then tried using two adapters (DP and DVI) to two traditional monitors.

Even with the clamshell closed, it could still only do one external monitor at a time?

 

[cmhsam]

Just plugged in my new mbp with m1 in my lg 49wl95c-w with usb c. Max resolution I can get is 3840x1080...!

I have also the latest intel mbp here and it works just fine in 5120x1440!

Anyone with the same problem? I know there is "always" a problem with apple and ultrawide. The old MacBook (2017) by my girlfriend also only works in 3840x1080. But I really thought the new mbp m1 which I able to run 6k 60hz should be able to run 5120x1440 (which is less than 4k!)

I had the same issue on my 16” pro and had to download a 3rd party app to force resolution to 5120x1440. Forgot the name of it but it’s rather popular just is escaping me right now.
Once I used the app it worked fine. I don’t have the 49” any longer so I can’t test on my m1 13” Pro

 

[saulinpa]

Even with the clamshell closed, it could still only do one external monitor at a time?

Correct. System Information shows the internal display disappearing but still only one external. Only thing I can't try is a dock as I don't have one.

 

[saulinpa]

Just plugged in my new mbp with m1 in my lg 49wl95c-w with usb c. Max resolution I can get is 3840x1080...!

I have also the latest intel mbp here and it works just fine in 5120x1440!

Anyone with the same problem? I know there is "always" a problem with apple and ultrawide. The old MacBook (2017) by my girlfriend also only works in 3840x1080. But I really thought the new mbp m1 which I able to run 6k 60hz should be able to run 5120x1440 (which is less than 4k!)

Something funky. I have 2 LG 5Ks and one will connect at 5K but the other only 4K. Never mind. Playing with SwitchResX and goofed things up.

 

[fishkorp]

Anyone have the CalDigit Pro dock? The chart in this pages seems to imply it can use 2 external extended displays, unless I’m reading it wrong.

Apple Silicon Mac & CalDigit Dock Compatibility – CalDigit

www.caldigit.com