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External monitor support

D

Daoi

macrumors newbie
Feb 27, 2010
7
5
The single monitor thing seems pretty strict. Sidecar did not work for me while running off an external monitor with the laptop closed in clamshell mode. Personally, it's a bit of a bummer, but I'll make do. This machine is just supposed to tide me over for another year at least until I think it's worth jumping on board an iMac or 16 inch MPB after they make the Apple Silicon switch.

Still, it does seem like a pretty unreasonable restriction given that the much weaker Intel MacBooks don't have such a limitation.
 
I

Idec50

macrumors regular
Feb 22, 2019
108
50
TX
Krevnik said:
After seeing some of the issues around UW and the like, I'm curious about this too.

I've got an LG 38GL950 that I use between my Mac and a Gaming PC, and I've gotten used to running 3840x1600@120Hz on the Mac side as well. That eats pretty much all the bandwidth DisplayPort 1.4 offers, and Apple doesn't actually say if they support 1.2 or 1.4 with the new machines. :|
Click to expand...

I think I could live with one external monitor if I had that monitor. I'd love to hear if someone tests the M1 with it.

As an aside, how do you like it? Is the contrast OK? I have a Dell 34" ultrawide and a gaming 16:9 1440p monitor that I currently run simultaneously off my '17 MBP. It's a bit too much but my code editor needs just a little bit more space to just use the 34" and man it's hard to go back to the low refresh. Can you run another monitor off a dock while running the 38"?
 
S

SteelBlueTJ

macrumors 6502
Apr 2, 2012
445
67
USA
The new M1 Mac-Mini still supports two 4K displays correct? This thread is kind of hard to follow as different people are talking about each MBA MBP MM.
 
J

joevt

macrumors 604
Jun 21, 2012
6,967
4,262
IgorK said:
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."
Click to expand...
They say it can it power two displays but don't actually get it to do that. That's not how you do a review.


fishkorp said:
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 www.caldigit.com
Click to expand...
Two displays but mirrored. This seems to imply that it's using an MST hub in the case where there is only one DisplayPort signal available as is the case when the dock is connected to a USB-C host or a Thunderbolt host that has only one DisplayPort connection. The page has a picture of the Thunderbolt host case - which allows for extended dual 4K displays, and the USB-C host case which allows for dual extended HD monitors (but probably single mirrored 4K 30Hz displays for macOS since macOS does not support MST for multiple displays).

I would like verification that the MST hub kicks in for Thunderbolt connection mode when only one DisplayPort signal is present. Does it use Titan Ridge controller to allow both USB-C and Thunderbolt hosts? If it uses Titan Ridge, then why are the ports only DisplayPort 1.2? Is the MST hub only DisplayPort 1.2? A DisplayPort 1.4 MST hub would allow higher resolutions than those listed on the page (and even greater resolutions for GPUs that support DSC).


ahlucas said:
so does it run true 5k res to a single LG UltraFine 5k? or is it forced to only 4k? (thanks!)
Click to expand...
Forced to 4K probably since LG UltraFine 5K requires two DisplayPort connections over Thunderbolt.

CORRECTION: M1 Macs have two DisplayPort connections to Thunderbolt, which can be used to provide full resolution (5K) 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.

Jester_A said:
I just got my Mac mini today and connected it to two external monitors, however only one of them are 4K 32 inch screen and the other full HD 27 inch screen. Works like a charm.
Click to expand...
You mean one monitor to the HDMI 2.0 port and another to a Thunderbolt port. There was no question about that working.

Jester_A said:
Had to buy new since my MacBook Air 2019 couldn't have both monitors working at the same time. Or I should say I could put in second monitor but if I turned it off, it wouldn't start again.
Click to expand...
Your MacBook Air 2019 should have had no problem with two external displays 4K 60Hz or less. You probably had a bad display/cable/adapter.

saulinpa said:
Apple hides the true resolution and normally SwitchResX shows but that isn't working. I can't find the command line that will pull the clocking information. Need to find some screen time looking at high res images to compare.
Click to expand...
At least one person said SwitchResX does work. What happens when you try to use SwitchResX?
Does the following command work?
/System/Library/Extensions/AppleGraphicsControl.kext/Contents/MacOS/AGDCDiagnose -a > AGDCDiagnose_M1.txt 2>&1


saulinpa said:
MacOS lies about resolutions. Yes, it shows 5120x2880 on my M1 but that is the "back buffer" or something like that. Going through old TB2 it shows the same thing but using SwitchResX it shows actual of 3840x2160.

All functions appear working for the 5K. Camera, microphone, speakers, USB keyboard, SuperDrive. Through System Info charging says it is 85watts.
Click to expand...
back buffer - you mean framebuffer. The framebuffer can be any size and is scaled to the output signal size. In this case 5K is scaled to 3840x2160. To get 5K on the LG UltraFine 5K requires two 2560x2880 DisplayPort signals (dual link SST) but the M1 Mac can only provide one over Thunderbolt.

Cariffo said:
But, can you connect 2 so that one mirrors the laptop display and the other acts like an external?
Click to expand...
I don't think so. I think it would be complicated. The signals would have to be identical or there would need to be an MST hub involved. In either case, there would need to be some switching as well.

An MST hub in a dock or by itself does mirroring internally (or macOS sees the two displays connected via MST and creates MST streams consisting of a stream that is duplicated for each stream - I'm not sure I've seen evidence that macOS is responsible for the duplicated streams - it may be all up to the MST hub - I don't know exactly how an MST hub works in this case).

saulinpa said:
No. A mirrored display still counts as a display.
Click to expand...
Maybe not in the case of a MST hub - if the MST hub does the mirroring work.

dustyblueheron said:
Does anyone know if a “classic” Apple Cinema HD Display (23”, dual-link DVI) will work with the M1? I am currently using it with a 2015 MBP, using a DVI to MiniDisplayPort connection. Seems it should work with a MiniDisplayPort to USB-C adapter?
Click to expand...
Just use a HDMI to DVI adapter. The 23" display is single link DVI which is the same as HDMI. Dual Link is required for resolutions greater than 1920x1200 such as the 2560x1600 of the Apple 30" Cinema Display. Your idea of a USB-C to Mini DisplayPort (female) adapter with the DisplayPort (male) to DVI adapter connected to the DVI cable of the display should also work. There exists USB-C to DVI adapters and more expensive USB-C to dual link DVI adapters.

Krevnik said:
I've got an LG 38GL950 that I use between my Mac and a Gaming PC, and I've gotten used to running 3840x1600@120Hz on the Mac side as well. That eats pretty much all the bandwidth DisplayPort 1.4 offers, and Apple doesn't actually say if they support 1.2 or 1.4 with the new machines. :|
Click to expand...
To support XDR at 6K 60Hz with one DisplayPort connection requires DisplayPort 1.4 with DSC. For 6K, only HBR2 with DSC is required. So the real question is, do the M1 Macs support HBR3 (for 5K 60Hz or 8K 30Hz 8bpc) and HBR3 with DSC (for 8K 60Hz 8bpc)?

To test for HBR3, you can try 8K 30Hz, 5K 60Hz, or 4K 120Hz (or at least anything over 4K 100Hz). Testing for HBR3 with DSC would require higher refresh rates. You have to make sure it's not using chroma sub sampling instead of DSC.
 
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D

DenBeke

macrumors regular
Aug 11, 2011
192
8
Antwerp
OWC states that their docks will support dual 4k displays on the M1 Mac: https://eshop.macsales.com/blog/67853-owc-thunderbolt-apple-silicon-m1-macs/

Need more ports? OWC provides the solutions you need to get the job done. On the go and need something that slips into your pocket? The OWC Thunderbolt 3 mini Dock lets you connect up to two 4K displays, two USB-A devices, and Ethernet. Want to build a workstation for your new MacBook Pro? With a single cable, the Thunderbolt 14-port dock lets you connect displays, drives, audio, mics, and headphones – all while charging your laptop.
 
C

cmhsam

macrumors 6502
Jul 14, 2008
448
70
DenBeke said:
OWC states that their docks will support dual 4k displays on the M1 Mac: https://eshop.macsales.com/blog/67853-owc-thunderbolt-apple-silicon-m1-macs/

Need more ports? OWC provides the solutions you need to get the job done. On the go and need something that slips into your pocket? The OWC Thunderbolt 3 mini Dock lets you connect up to two 4K displays, two USB-A devices, and Ethernet. Want to build a workstation for your new MacBook Pro? With a single cable, the Thunderbolt 14-port dock lets you connect displays, drives, audio, mics, and headphones – all while charging your laptop.
Click to expand...
Oh snap. This is good news. Hopefully Caldigit will support via firmware.
 
J

joevt

macrumors 604
Jun 21, 2012
6,967
4,262
DenBeke said:
OWC states that their docks will support dual 4k displays on the M1 Mac: https://eshop.macsales.com/blog/67853-owc-thunderbolt-apple-silicon-m1-macs/

Need more ports? OWC provides the solutions you need to get the job done. On the go and need something that slips into your pocket? The OWC Thunderbolt 3 mini Dock lets you connect up to two 4K displays, two USB-A devices, and Ethernet. Want to build a workstation for your new MacBook Pro? With a single cable, the Thunderbolt 14-port dock lets you connect displays, drives, audio, mics, and headphones – all while charging your laptop.
Click to expand...
I think they copy and pasted that description from elsewhere and did not make changes to address the limits of the M1 Macs.
I think they mean up to two 4K displays can be used if the computer has Thunderbolt ports that support two displays. The M1 Macs only support one display from Thunderbolt.

cmhsam said:
Do you know which display link hub? Their website seems to have several including OEM.
Click to expand...
All the DisplayLink devices should work with the DisplayLink drivers installed.

DisplayLink macOS Software for Downloads Section | Synaptics

WindowsmacOSAndroidChrome OSUbuntuCorpo
www.displaylink.com www.displaylink.com

I suppose you should try for the ones that support the max USB speed of 10 Gbps. Actually, they don't get faster than 5 Gbps. The DL-6000 series of chips seems to be the latest and most capable. They can do up to 5120x2880.

DisplayLink Products | Synaptics

Where to buy DisplayLink productsDisplayLink technology appears in a wide range of products from the world's leading PC and peripheral brands. It features in docking stations, monitors, adapters, and more.Products with DisplayLink technology are supported on Windows, macOS, Android and Chrome OS...
www.displaylink.com www.displaylink.com
 
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nothingtoseehere

nothingtoseehere

macrumors 6502
Jun 3, 2020
455
522
joevt said:
I think they copy and pasted that description from elsewhere and did not make changes to address the limits of the M1 Macs.
I think they mean up to two 4K displays can be used if the computer has Thunderbolt ports that support two displays. The M1 Macs only support one display from Thunderbolt.
Click to expand...
I wrote to OWC asking just this. Will post the answer in the case I get one :rolleyes:
 
S

saulinpa

macrumors 65816
Jun 15, 2008
1,269
777
joevt said:
At least one person said SwitchResX does work. What happens when you try to use SwitchResX?
Does the following command work?
/System/Library/Extensions/AppleGraphicsControl.kext/Contents/MacOS/AGDCDiagnose -a > AGDCDiagnose_M1.txt 2>&1
Click to expand...
SwitchResX works to set resolutions but doesn't provide details. Says "System doesn't provide detailed information about this resolution."

AGDCDiagnose just gives an error message.


joevt said:
back buffer - you mean framebuffer. The framebuffer can be any size and is scaled to the output signal size. In this case 5K is scaled to 3840x2160. To get 5K on the LG UltraFine 5K requires two 2560x2880 DisplayPort signals (dual link SST) but the M1 Mac can only provide one over Thunderbolt.
Click to expand...
From https://www.khronos.org/opengl/wiki/Default_Framebuffer: "The front and back buffers represent a double-buffered framebuffer. The front buffer is, more or less, what you see on the screen. The back buffer is the image that is typically rendered to."
 
A

askabob91

macrumors member
Sep 21, 2008
63
28
OWC put out a press release saying their docks have compatibility with the M1 macs. Can anyone confirm this? If so, I will order one as a dual monitor setup is important for my workflow.
 
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Krevnik

Krevnik

macrumors 601
Sep 8, 2003
4,101
1,312
saulinpa said:
From https://www.khronos.org/opengl/wiki/Default_Framebuffer: "The front and back buffers represent a double-buffered framebuffer. The front buffer is, more or less, what you see on the screen. The back buffer is the image that is typically rendered to."
Click to expand...

I probably wouldn’t go up against joevt on this one. I know enough about the graphics pipeline to be dangerous, and he still keeps fact checking me since I’m rusty, and the last few years have made things more complicated than when I was learning this stuff. :)

The thing is, last time I paid close attention, the front and back buffers are identical. The reason being is that it’s much faster to simply swap the two buffers than it is to copy between them. This to me suggests that any scaling is done as the front buffer is being read to the output. So in this case, framebuffer is really the easier term to use. Maybe being a bit pedantic though.

joevt said:
To support XDR at 6K 60Hz with one DisplayPort connection requires DisplayPort 1.4 with DSC. For 6K, only HBR2 with DSC is required. So the real question is, do the M1 Macs support HBR3 (for 5K 60Hz or 8K 30Hz 8bpc) and HBR3 with DSC (for 8K 60Hz 8bpc)?

To test for HBR3, you can try 8K 30Hz, 5K 60Hz, or 4K 120Hz (or at least anything over 4K 100Hz). Testing for HBR3 with DSC would require higher refresh rates. You have to make sure it's not using chroma sub sampling instead of DSC.
Click to expand...

The highlighted is the bit I was curious about, really. Another thread linked to Reddit where a user was spitting out 1080p@2x to a 4K display at 120Hz, which suggests that uncompressed HBR3 is supported. That’s good news.

But yes, would probably be more clear with some detailed logs from the diagnosis tools (assuming those work on M1 machines, I’m seeing conflicting reports).

Idec50 said:
I think I could live with one external monitor if I had that monitor. I'd love to hear if someone tests the M1 with it.

As an aside, how do you like it? Is the contrast OK? I have a Dell 34" ultrawide and a gaming 16:9 1440p monitor that I currently run simultaneously off my '17 MBP. It's a bit too much but my code editor needs just a little bit more space to just use the 34" and man it's hard to go back to the low refresh. Can you run another monitor off a dock while running the 38"?
Click to expand...

If you are fine with the contrast in Apple’s displays, the LG will be fine. The contrast ratio is very similar between LG’s current IPS panels, and the IPS panels Apple uses in their displays. I may be remembering wrong, but Apple’s using LG’s IPS panels for their laptops and iMac today, aren’t they? I went with this one because:

1) It supports 10bpc, which I wanted for working with Affinity Photo and similar apps.
2) It supports high-refresh for gaming with my Windows rig, and handles both G-Sync and FreeSync.
3) It’s large enough that I haven’t had any desire to go dual monitor, but is still an improvement over a 27” display by itself.

I’m not a huge fan of dual monitors. I’ve used 2x27” displays as part of an iMac Pro workstation, and I honestly prefer the 38” UW to that. It doesn’t have quite as much space, but for me, 2x27” starts getting to be too much, and it’s hard to use the space effectively. While with a 38”, I can have Xcode + simulator up, and easily have room for everything I need to see at the same time.

I only run one display at the moment. The 38”, plus the speakers I have take up most of my desk. I do have a passive DisplayPort switch I use to switch the monitor between my Mac and PC which lets me get the nice 10bpc, 120Hz experience on both machines.

But I can’t imagine that you couldn’t run a second monitor off a dock. The 38” only needs one DisplayPort stream, but the catch is I’ve yet to find a TB dock that supports HBR3 fully, so running the 38” through a dock will limit you to either 85Hz at 10bpc, or 100Hz at 8bpc.
 
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