My journey for dual displays with my M1 Pro Mac (2021) | Hacker News Reader

My journey for dual displays with my M1 Pro Mac (2021)

derekseaman.com

110 pointswalterbell139 comments

It's kind-of crazy that macOS still doesn't support DisplayPort Multi Stream Transport - the ability to drive multiple displays with a single DisplayPort cable. That kind of thing fits Apple's ethos very well, and they are heavily involved in the DisplayPort spec and support.

My MacBook Pro (15-inch, 2017) has two 34UM88s chained on a single Thunderbolt port somehow.

That's TB daisy chaining, not DP's multi thing

Whoa, how?! Everything I’ve read indicates that Apple MacOS does not support TB (or was it USB-C?) daisy chaining

My theory is they want to you buy Thunderbolt displays. They get a cut of sales of Thunderbolt, but not a cut of DisplayPort, since it's a standard that is free of royalties. There's literally no other reason I can think of not to support MST out of the box on these laptops. Especially if they are involved in working on the spec.

Thunderbolt has been royalty-free since 2019, when it was licensed to the USB-IF to be used as the basis for USB4.

https://arstechnica.com/gadgets/2019/03/thunderbolt-3-become...

(I also suspect that Apple's cut wasn't huge to start with; Thunderbolt was developed with Intel, and Intel likely got the lion's share of royalties given that they were the ones actually selling the Thunderbolt controllers and seem to have been the driving force behind Thunderbolt 3.)

I have a USB C monitor and a second monitor connected to the first monitor with a DP cable. The USB C cable is connected to a ThinkPad x270 (a machine from 2017) running linux. Am I missing something regarding TB vs USB C + DP, or are you saying that this setup wouldn't work on a newly released MacBook? It sounds pretty unbelievable to me.

Yes. Apple doesn't support DP daisy chaining and they only recently added support for variable refresh rates on Macs despite it being a thing in the monitor space for 8 years. If their own products don't use it they don't care about it.

Surprised there was no mention of CalDigit docks. One of my desks has an old TS3+ that drives 2x 2560x1440 monitors perfectly from an M1 Pro machine, and it was rock solid when used with older Intel Macs and Windows PCs too. It’s Thunderbolt 3, but CalDigit recently released a TB4 version.

I haven’t yet tried dual displays with it but my other desk is using a Lenovo ThinkPad Thunderbolt 4 Dock and it’s also been solid.

I suspect that a lot of the more mass market oriented docks cut corners and don’t implement specs quite to full compliance which leads to weirdness like seen in the article.

When I upgraded to an M1 MacBook Pro, my CalDigit TS3+ no longer supported dual external monitors and I had to buy a new dock: https://www.caldigit.com/apple-silicon-mac-and-caldigit-dock...

That’s because regular M1’s can only support two displays. In the case of MacBooks, that’s the internal display and one external.

M1 Pro and Max do not share this limitation.

Apparently DisplayLink adapters get around this limitation.

Can confirm DisplayLink works fine

Sounds like you didn't do enough research. I am using a CalDigit TS3+ with 2x4K and 1x1080p external displays on a M1 Macbook Pro to write this comment. It is not difficult at all to do and took less than five minutes of searching for me to find the guides and instruction videos when I decided to upgrade my Macbook to Apple Silicon.

What cable and connector types are you using please?

All monitors have DisplayPort and HDMI inputs, using DP<->DP, usb-c<->DP, and usb-c<->HDMI (latter for the 1080p display). Also using DisplayLink Manager to drive the 2nd and 3rd extra displays.

Using a CalDigit right now to power two monitors on an M1 Macbook Pro. It doesn't go above 60hz (my monitors are 165hz) but I'm still happy with it. Has an ethernet port too, which is great.

Are you using HDMI or DisplayPort and which type of cables (e.g. do they convert connection type, or for example the same on both ends)? Asking as I have the same doc and about to get an M1.

I also have this dock driving two Dell 4K displays at 60hz from an M1 Max. Using DisplayPort cables I had to use one TB port and one DP connector on the dock, but miniDP on the monitor side (full DP should work too, these were the cables I had).

Two HDMI cables plugged into the CalDigit port, which goes into a USB-C port in my MacBook. I also have an ethernet cable plugged into it as well.

There was a period of time where the TS3+ was completely unavailable. Our IT people were saying that the manufacturer couldn't get parts to build them. :( I was lucky enough to get one before that happened and can say it works great. I'm using a SUW49DA from Viotek. The only issue I have is that something keeps waking the monitor up overnight but not sending a video signal. This eventually causes the monitor to shutdown and stop waking up until it's physically power cycled ( i.e. unplug/replugin). Otherwise, it's been great.

Early on especially almost all of the docks had the exact same chip on the inside.

Has anyone else switched from using 2 monitors to just using one big extra wide one? I've found it to be just as good as two, if not better. Maybe a little more expensive than buying two, but it's been worth it.

I switched to an ultrawide and will never look back. My last setup was 2 monitors. Having 2 1440p monitors basically stuck together to make an ultrawide is a dream come true. It’s 100% worth the switch.

My M1 Air runs my ultrawide at 60hz and is buttery smooth.

I've long preferred one large monitor. Which ultrawide do you have?

I have an Acer XR382CQK which is 3840x1600 and can do 75hz. I can’t live without it now.

I bought this one but it was overkill for my needs. I think the model below this one is a better buy. They were out when I bought it.

https://www.microcenter.com/product/639902/lg-34gp950g-34-2k...

I highly recommend the Dell UltraSharp U4919, of which I currently have four (two at home and two at work). Almost my entire department switch to them as soon as they came out.

My other ultra-wide is an ASUS PG348Q. It's crazy how that monitor felt huge when I got it, but it just seems tiny now.

Two 49" monitors? At the same time? That sounds crazy! I like the Dell UltraSharp though.

IMO, 1440p is too low of a pixel density for productivity. My first 1440p monitor was 10 years ago. If only 2160p ultrawides weren't prohibitively expensive.

Agreed, 4K is my favorite resolution. I was going to add above that the only way I’d buy another monitor was if it was a 4K or higher ultrawide.

I use an ultrawide monitor alongside a vertically-oriented monitor (for code review) - I find this setup fits my personal and professional needs perfectly!

I like my single 32” at home better than my dual 27” at work.

I’m running dual 27 4k and considering a larger single monitor, what have you like about it?

I did this and I agree that it's a better solution (for me). Keeping your neck twisted to the side for long periods of time is not good. With an extra wide monitor you can pull over windows to the center if you want to focus on them for any significant period of time.

I love the single ultra wide over two monitors. The only problem I have is when presenting. I need to show several apps at once but if I share my entire screen it obviously looks horrible for everyone else. The solution is to open my MacBook and share from there. Not a huge deal, but a bit annoying.

I have had a 43" monitor at work and at home for a while, and the solution I've used throughout the pandemic has been to share only a region of the screen, or to share a single application or window, which I often shrink down to a "laptop" size" in order to share my screen with colleagues. That still leaves plenty of real estate around the "shared" window that is not visible to others, but is useful to me.

I have a shortcut setup in my window manager app to resize the current window to 1920x1080 specifically for screen sharing.

By “window” do you mean “display”?

I wish that when you shared an app window, Zoom would let you scale that to fit the full screen share. That way you could present a reasonable image of a window to viewers while using an ultra-wide monitor.

No, I mean the window. Usually I’m sharing chrome or a code editor via zoom.

Zoom lets you share a region of your screen if you click the advanced tab when sharing.

Yeah, sadly we use Google which does not.

I share a tab/window and resize that window to be approx 16:10. Shows up nicely for others and I can still see the rest of my screen.

If I had another window open for chat/notes/emails I can still have that at half my ultrawide and just deal with a bit of overlap on my end

I did the same but not being able to share a terminal and a browser window at the same time is tough.

Ended up using OBS and sharing the obs preview window instead. This lets me add fun gifs and overlays as well to my screen for loading or success.

I wrote this[0] post on how I use OBS to share a 1080p sized portion of my upper left ultrawide monitor through Microsoft Teams. If you can share just a specific window, then this should work with google meet.

https://jamesdesmond.org/posts/teams-screenshare-mac/

I haven’t, for a few reasons.

- The logical “partitioning” of workspace between displays is a nice tool for organization, particularly when combined with Spaces/virtual desktops

- I work from home, so my main display does double duty between work and games, which is a problem with the latter with many games having bad or lackluster ultrawide support

- Ultrawides restrict display selection quite considerably and often require concessions on things like color performance, backlight bleed, pixel response times (especially curved ultrawides, which seem to all use VA panels which are known for smearing and slow response times)

> The logical “partitioning” of workspace between displays is a nice tool for organization, particularly when combined with Spaces/virtual desktops

Use a better window manager.

That wouldn’t really work for me. The physical separation (and different display angle that brings) and ability to set different wallpapers per workspace per monitor are important and can’t be reproduced with a window manager.

I also just don’t like micromanaging my window arrangement or having the WM try to do it automatically (and usually get it wrong).

That's a good point. I personally like having one horizontal and one vertical setup.

> I also just don’t like micromanaging my window arrangement or having the WM try to do it automatically (and usually get it wrong).

How is that solved by adding a monitor? If I used two (I don't any more) I would still use a (better than macOS default) window manager.

Both an extra monitor and an ultrawide add more space for windows, but the naturally partitioned nature of a second display combined with virtual desktops also provides low effort organization.

So in my typical usage, secondary/tertiary/etc windows go into purposed virtual desktops on the second monitor — e.g. one virtual desktop for documentation, another for chat, etc. This allows me to swap out the sets of less important windows independent of the main display’s workspace, with practically zero management overhead (just assign apps to virtual desktops during initial setup).

The extent of third party window management I use is Moom, which I use to snap maybe 3-5 windows across my entire workspace into specific locations/sizes. Something that emulates a Linux tiling WM like Amethyst would drive me insane.

> I would still use a (better than macOS default) window manager.

What are some of the alternatives that you would recommend?

I use Divvy (https://apps.apple.com/us/app/divvy-window-manager/id4138575...).

It's probably the simplest one. Draw the shape you want on a grid, assign a global hotkey to each shape (fullscreen, top half, bot half, left, right, etc.), press the hotkey to move current window into that shape. Press the same hotkey again to move it between monitors.

It's funny how you get so used to your own dev environment and all the global hotkeys you might have and then completely take it for granted until you use a computer with it.

For macOS? I no longer use have any Macs in use, but I used yabai when I did.

On Linux I use i3.

I've been using the LG C1 48", it's a little too tall so the upper portion of the screen rarely sees use outside of full screen video/games, but otherwise it's great. Although my opinion may change if it starts burning in significantly

I don't have experience with this on a Mac but I've been trying this recently on Windows. Window snapping and edge-of-screen behaviors make using multiple monitors slightly better than using a single monitor that is just as large.

Fancyzones makes this much more tolerable but misses a few minor scenarios.

I replaced two 1440p monitors with a single ultrawide and complemented it with a tablet on my desk showing hdmi through deskreen, usually showing a chat window. I guess technically I still have two displays but it takes up less desk space overall.

On the positive side the displays are centered in front of me better and I can fiddle with the tablet placement much more easily than a real monitor. I've experienced neck strain working for extended periods with windows on the edge of the farthest dual monitor.

I sometimes run an ultrawide (3440x1440) off my M1 Air. It works... ok. MacOS doesn't output more than 50hz, and every hour or so the display will flicker off and on. I haven't decided if its an issue with the M1, or an issue with the hub I'm using, but its not a big enough concern for me to justify investigating much further.

I personally feel that 21:9 ultrawides aren't quite as good as dual 16:9 displays for productivity. But they're fine. My biggest complaint is that most people would reasonable center their monitor on the desk. If you run 2x16:9, you can have one centered, and one off to the side, which allows you to mostly look straight forward and have a natural primary/secondary setup.

At 21:9, this setup is weirder; either you size your primary window (browser, code editor, etc) to ~16:9, left-or-right-align it, then you have to slightly crane your neck, or you center-align it and you're left with slivers of screen real-estate to the left-and-right. Or you can shrink the primary center window, approaching maybe a max of 7:9 for all three windows, which is maybe rarely useful for some applications. Or you can maximize the window, and in most applications you get tons of unused space. Or you can physically offset the monitor on your desk, which looks weird. There's just no solution that works "great" especially given these displays are oftentimes at a small premium over 2x16:9.

I think something like the Samsung Odyssey CRG9 would be much higher productivity in ultrawide, with its 32:9 aspect ratio. There, you could run a ~16:9 centered primary window, and still have ~8:9 canvases to the left and right, which is enough horizontal estate to comfortably have a terminal, Spotify, browser, etc. Its also relatively affordable (~$1100), though given you can find solid 1440p 27" monitors for $200-$300, you're effectively cross-shopping 3x16:9 displays. Still definitely a "luxury" buy. Its ultimately unclear to me that it would be better, and not just "differently similar".

I think it's your dock. I have an LG 3440x1440 (and a Dell at work) that works fine over USB-C directly to my M1 Air.

I tested my 3440x1440 monitor with M1 Air. I found that fonts are rendered without anti aliasing and looked not good at all. Do you have similar issues?

I have 3440x1440 and it works fine - I run 100 hz on my work MBP. Which is Intel, granted, but 3440x1440 is strictly less than 4k, and we don’t see an epidemic of people noticing that their 4k monitor is running at 30 hz on their M1 MBPs.

50 hz happens to be the limit of hdmi 1.4b (at 3440x1440), it sounds like somewhere in your chain you have something that is running at legacy speeds. Could be your dock, could be your monitor, could be an active adapter cable.

I’d start by making sure you’re running DisplayPort and not HDMI. HDMI is more or less a “legacy” port these days, as far as workstation usage is concerned. And unlike DP there is no embedded HDMI support in USB-C Alt Mode so any sort of USB-C to HDMI adapter needs an active converter - which may be your hdmi 1.4 bottleneck.

(note that the "passive" HDMI mode that full-size displayports offer - aka DP++ - is an optional part of the spec. It's so widely implemented on full-size ports that most people don't realize it's optional, but embedded DisplayPort implementations like eDP or USB-C Alt Mode, Thunderbolt, etc don't implement this feature.)

Anker sells a relatively cheap dongle that will do 100Hz ultrawide over HDMI.

I'll switch as soon as High DPI ultrawide is a thing.

I know there's the LG 5Kx2K monitor, but MacOS can't drive it at 6880x2880 which is the scaling option I'd want - It's less pixels in total than a Pro Display XDR, but I guess their logic is "if (width > 6k) { don't allow }"

You can use better dummy to achieve a similar resolution: See here https://github.com/waydabber/BetterDummy and this MacRumors thread https://forums.macrumors.com/threads/m1-mbp-lg-34-inch-ultra...

I tried it on my M1 Mini + LG5K2K and soon disabled it again. The performance impact was noticeable in Lightroom and the display adapter config got in the way once I switched display input to my work laptop.

Let me rephrase that, I'll switch once I can do it in a non-hacky way.

It should be possible - 6880x2880 is fewer pixels than the Pro Display XDR, which an M1 MacBook Air can drive perfectly well.

Similar journey, but I went from two down to one 27" 4k. I found that I was getting distracted by all the extra open windows and time spent arranging them. Maybe it is just because I'm getting older, but I've found the key (for me) to productivity is getting back to doing just one thing at a time. It has taken a lot of discipline and a little bit of creativity to achieve this, but I think my productivity has improved.

I switched to a 34" UW UHD display, from 2x 24" - I definitely prefer it.

The Dell UltraSharp U4919DW is 32x9 with a 5120 x 1440 at 60Hz. I works with the MacBook as long as you do not use the HDMI port. I have mine hooked up either via a Thunderbolt 4 dock or a USB-C to DisplayPort cable.

You can test you got the full resolution by doing:

  system_profiler SPDisplaysDataType | awk '/Resolution/{print $2, $3, $4}'

On my MacBook Pro I have two ultrawides, and two HDPI 4ks, it's nice.

Having a single monitor messes up macOS's virtual desktop environment. Much easier to swipe between fullscreen apps with two seperate desktops.

I switched from 2 21.5" 1080p monitors to 1 40" 4k TV. At first it felt comically huge, but I found it great for both media consumption and working on huge documents. If I had a larger desk, I'd move to an AORUS FO48U.

I have gone one step past that. The really wide monitor gave me a neck ache as I'd persistently find myself wedging stuff at one end. It was also 1440p which is crap.

I now have a single 27" 4k monitor which has better text rendering and no neck ache.

I will buy a 27" 5k if Apple sell one.

Apple sells the LG Ultrafine 5k which is 27". It's not Apple made but iirc they worked with LG to design it. I really like mine, the high dpi is fantastic. I have a 27" 1440p next to it that is pretty much relegated to being a Spotify screen because looking at text on it feels vastly inferior to the LG.

I'm mostly interested in Apple selling one because the LG warranty and service support here (UK) is absolutely dire.

I have the LG38" connected via USB-C to CalDigit TS3 via Thunderbolt MBP (2019). It looks fine. Still wishing someone made a HD-DPI wide screen (AFAICT all wide-screens are low-dpi). Mac does a great job of scaling though (I'm set to 3200x1333)

I'm not sure which is better. I like there's no divider in the middle of my display area! Work is giving me two 27" monitors so we'll see how it goes.

The only complaint, which is minor but annoys me several times a day, ... It takes several seconds for the Mac to wake up. Meaning, I have a PC also connected to the LG monitor vs DisplayPort. If I switch over and press a key Windows wakes up immediately. When I switch back to Mac and press a key it's easily 3-4 seconds before I can even start typing. I'm pretty sure that's USB-C/Thunderbolt only issue and if I used Displayport or something that problem might go away but still surprised Apple finds this acceptable give their focus on UX. I guess I get the number of people using 2 devices is low. But, even if I don't switch away and just walk away but leave it on Mac, when I come back, it takes 3-4 seconds to wake up vs Windows which is instant.

Note: "wake up" is the wrong word because the Mac has not started sleeping. I have processes running. I hear notifications, etc. It's just something to with getting things to display again.

I use a 32" 4K monitor with my M1 Air and it's great.

I've got it just close enough to me to hit my max comfortable FOV (so I don't have to crane my neck to see parts of the screen) while still being unable to see pixels.

It's got a USB C port that can do 4k 120Hz (which is awesome) and puts out just enough charging power to keep my Air from draining while I'm using it.

At native 4K things area little small, but moving the MacOS scaling down one or two ticks is perfect.

Hard to imagine a more perfect setup, personally.

This is where I am now. 32” at native 4K, 1@ resolution, but with text size bumped up a bit on some windows. Internal monitor is the slack/mail/calendar display, work is on the big one. Even when I’m using the mini, with no internal, I don’t find that I miss having two monitors.

The few times I’ve used a 49 ultrawide, meh, I’m not impressed but it’s better than just the internal. I’d probably need to reset the window manager to do 1x4, rather than using thirds.

I think I’m a unicorn. 14” M1 Max, triple displays, albeit with two cables. We also have an M1 Pro in the house w/ CalDigit TS3 (non-plus), which is driving dual 4k’s without issue.

I’m confused why the author didn’t just purchase one of the cornucopia of Thunderbolt 3 (or 4) docks that do everything including display output.

Triple config (M1 Max): - OWC Thunderbolt 4 dock, connected to 2 4k displays, network, speakers, USB devices - 5k display connected direct to the mac

Dual Config (M1 Pro): - CalDigit TS3 dock, connected to 2 4k displays, speakers, ethernet, USB devices

Works perfectly, and we have no complaints about either config.

Why Is the 5k direct connect? Because there aren’t any TB docks that support 3x displays when pushing > 4k; I’m unclear if it’s technically possible.

I had previously run triple displays on a 13” Intel MBP using an eGPU. I wrote about that journey here: https://www.codevoid.net/ruminations/2020/09/27/three-displa...

> Because there aren’t any TB docks that support 3x displays when pushing > 4k; I’m unclear if it’s technically possible.

It’s not technically possible given the bandwidth available on a TB3/TB4 port. 5K display requires 22Gbps, the port overall is limited to 40Gbps, so not possible to get more than one on a single cable. Due to the way TB uses the available lanes in the cable, it’s also not possible to my knowledge to support a USB-C 4K monitor daisy chained off a 5K monitor either even though there’s sufficient bandwidth (22 + 15 < 40) to do so.

Thunderbolt 5 w/ it’s supposed 80Gbps support will change that.

my caldigit dock “works perfectly”. it consistently requires plug and unplug, opening laptop lid to unlock then unplugging and waiting and replugging then closing laptop lid, trying different usb-c port, and having to reboot to support higher than 60hz refresh rates. perfectly.

Exactly my M1 MBA 4K external display experience: "works perfectly."

I have heard from friends that the TS3+ is slightly less reliable than the TS3. Initially -- 2017-ish -- we had challenges with the monitors (Dell's) being weird. We updated the firmware on the monitor (no fix), and updated the cables to newer DP cables (Fixed it).

YMMV, of course.

Dell did not make a thunderbolt monitor in 2017. I'm still not sure if they do. You might be referring to running DisplayPort over USB 3 (with a type-c connector)

USB 3 video is a troublesome way to connect a monitor, with a lot of vendor incompatible techniques for signaling sleep/wake, charging, and obscure limitations on resolution/refresh. For example, for years Dell stated that their USB C monitors were not compatible with Apple devices.

Thunderbolt 3 seems far more reliable, in my experience.

Wasn’t implying they were TB; the dock has DP + USB-C (w/ DP alt mode) — those were the monitors connected to the dock (one via DP-DP, one via USB—C-DP cable. The one that ‘fixed’ it was the DP-DP cable)

It's possible the author is unaware that there are cables that have a USB-C (TB4) connector on one end and a DisplayPort connector on the other. This should directly support running DisplayPort 1.4 off just the dock they purchased without additional dongles. (Which would also work with the OWC TB4 dock you mention).

Possibly they had a specific need for actual DisplayPort ports on the dock though, and because they specifically wanted DisplayPort 1.4, that ruled out TB3 docks.

How do you like that OWC dock? It looks pretty nice. I also noticed that CalDigit has successor to your TS3 that looks pretty nice too.

I'm very happy with the OWC dock -- it's been rock solid, and in the eGPU/Intel config allowed single cable by daisy chaining the eGPU off the dock. I had a similar experience with their ThunderBolt hub (which is just 3 TB4 outs, 1 TB4 in).

I've theorized for a while that the OWC, Razer, Belkin, and Kensington TB4 docks are all the same (Razer sacrificed a USB port for RGB) -- they have the same basic layout, and same basic capabilities. The CalDigit TS4 looks like a different design, adding some more ports.

I have a friend with various TB docks w/ Intel Mac + eGPU, and have experienced a consistent issue when using a secondary USB-C DAC for audio. I haven't, but if that's your scenario, might be worth a pause.

Your assumption is correct. Those docks are all based on the Goodway DBD1100 [1]. When I was researching which dock to purchase myself, I came across this comprehensive list [2] of Thunderbolt docks which was super informative.

[1] http://www.goodway.com.tw/prodimg/edm/DBD1100.pdf

[2] https://dancharblog.wordpress.com/2021/02/05/usb4-tb4-docks/

Yes, I think the solution the author has settled on is unnecessarily complicated architecturally? I'm not sure how the OWC adapter is working seeing as it's TB3 and I thought TB3 only supports one downstream TB port per device - is the second DP port (or both) somehow connected to the PCIe lanes?

I think the whole point of TB4 is that you can plug multiple monitors straight into the dock.

Yep - this is exactly what I use!

Although I plug both into the Mac directly.

The article confused me too with its talk of dongles and DP ports on docks. Just get the right cables man! :-)

Side note - TB docks are still stupidly expensive, even after Intel changed the licensing which was supposed to make them cheaper. If I'm remembering that correctly.

Side side note: DisplayLink for 4K on M1 macs is still not working right! :-(

I might be a bit stranger - I swap back and forth between a Windows desktop PC and an M1 MBP with the same dual 27" 4K displays (both LG, one is a 144Hz and the other is a 60Hz panel). Eventually I'll retire the desktop PC in favor of a Thunderbolt 4 Windows laptop and swap between the two of them. I use a TS3+ dock and everything works using a single TB cable.

> I think I’m a unicorn. 14” M1 Max, triple displays, albeit with two cables. We also have an M1 Pro in the house ...

you're not a unicorn - both the M1 Max and Pro explicitly support multiple external monitors.

the base M1 laptop model that was released only supports one internal and one external. if I close the lid of the laptop, I can only use one monitor even with two cables.

I find the displaylink adapter works extremely well as a workaround here.

But sadly 4K is still not properly supported on M1 macs!

Full 4K modes lose bits making it unusable for many things.

And scaled modes are not true hiDPI modes!

So QHD looks very pixelated on a 4K display!

I have the CalDigit TS3 Plus and two identical Dell 24" displays (U2415). One monitor is attached via TB3/USB-C to DP, the other DP to DP. This setup worked with a 2018 Intel MBP without issue. With an M1 Pro MBP, the monitors are detected, but will not come out of sleep.

I also have a Belkin Thunderbolt 3 Express Dock HD. Hooked up the same way, I experience the same behavior from the monitors. Both show up in display settings, but will not come out of sleep.

Interestingly, I see the same issue if I disconnect one of the monitors from the dock, i.e. only one monitor is connected to the dock. Basically, neither of my external monitors will work if they are connected to the M1 Pro through a Thunderbolt dock. Both work when plugged into the MBP directly, so I suppose I could connect one via HDMI and the other using TB3/USB-C to DisplayPort, with the rest of my peripherals connected through the dock, leaving me with one free USB-C port. Not exactly the dream.

I also have a Cable Matters USB-C Dual 4k DisplayPort dock. This is not a Thunderbolt dock. Both external monitors work, but the dual monitor functionality depends on DisplayPort MST, which Apple is infamous for not supporting. So, the external monitors show up as a single mirrored display.

CalDigit support told me that this was common when attaching two identical make/model external monitors to their dock. They suggested I attach dissimilar external monitors, but I don't have another DisplayPort monitor. Also, I don't want dissimilar monitors.

I guess I'm surprised this is a problem with the M1 Pro/Max. My understanding is that it was even worse with the original M1. Maybe Apple's user research shows that most people are not using multiple external monitors (or in my case: any external monitors) via Thunderbolt dock. Otherwise, I wish there was more writing from Apple explaining what configurations should work and why they might not.

I've come to the realization that getting multiple external monitors and then more than one set of them to work right is not a "trivial" problem. Any decision is going to be wrong or might result in a compromise or bad outcome.

The CalDigit support response sort of suggests that some monitors (or interfaces that fake it) aren't providing unique EDID data.

EDID is supposed to contain a serial number. Connecting two monitors that claim to be the "same" device because the serial number is the same is going to be a problem - which one is on the left or right? How can you know / remember? Basing it on which "port" they are plugged into will also lead to frustration if they get swapped or a hub is used.

What if you have two sets of the same monitors at home (L and R), and two more of the same monitors at work (L and R). What do you want the experience to be? (mapping Apps to the correct displays when moving environments is also an issue that, ahem, hasn't always worked well!)

I'd want (and I've been TOLD) that plug and play experience needs to be the same at home and at work after the manual setup of the monitor placement. At home the built-in display is on the right, with built-in switched to the left at work. NB: I really cannot see how to do all of this unless the monitors can uniquely identify themselves.

Recording or noting these setups / placements also could be a technical challenge - plugging in external monitors in a different order, including timing, does that create a new monitor "environment"? Given what I've observed, I think it does.

My wife has a setup like the above with 2x LG 4K displays (two USB-C thunderbolt cables / connections) in two locations. It has been "mostly working, but slow" for her old Intel MacBook pro or "working well" for a newly acquired Apple Silicon MacBook Pro with the current macOS Monterey.

Doing the numbers, home has 7 configs. IR=Internal-right. (I), (IR, LH), (IR, RH), (IR, LH, RH), (LH), (LH, RH), (RH). Work also has 7 configs. IL=Internal-Left. (I), (IL, LW), (IL, RW), (IR, LW, RW), (LW), (LW, RW), (RW).

Ramble: For the (exaggerated) 400 open windows any display plug/unplug event this is going to cause a re-render storm for a new DPI, colour depth and location for every window for each plug / monitor transition. Ouch.

I am dinosaur and this is an X11 flashback. How can or does any of this even work for Linux? An X11 app opens a connection to a "Display" and the DPI (size), colour depth and other params used to be "fixed" at that point in time, the client does all of the rendering for the window, providing a bitmap to the X11 server. In the past it was not possible to move windows between incompatible display parameters - making dynamic changes not possible. How does moving windows between monitors of different DPI / colour depth now work in X11? I need to look into this. Prediction: I likely will be a casualty in the war of display rendering.

Final ramble. With some of these new "standards" (looking at you, USB-C), it seems the goal is to get the license payment but there is no requirement that your product passes a conformance test in order to ship it.

(Unrelated to the subject, but this website is a perfect example of why reader mode is a required feature for web browsers.)

I mean did he try to just daisy chain them? He claims that he wanted to use DisplayPort 1.4 for connectivity. But the monitors do support daisy chaining over thunderbolt, and he also states that. But why not daisy chain? I mean I get that it's frustrating to get the thing working with DisplayPort, dongles and docks. But the best solution was right in front of him?

I believe macOS on Apple Silicon or Intel does not support DisplayPort MST (Multi-Stream Transport) which is required for daisy-chaining to work.

MacOS supports MST mirror (which imho is mostly useless outside niche uses), but not MST extend.

Over Thunderbolt at least. I imagine it might subpar on non supported stuff.

Not sure what you mean, Thunderbolt is unrelated to MST.

MST mirroring works with all the MST capable DP monitors I’ve tried (half dozen or so), but have never got MST extend to work.

I suppose it's the common knowledge that Mac OS doesn't support MST properly and author assumed it applied to Thunderbolt docks as well. This is on Apple for not implementing that, because it's not the hardware. Intel Macbooks work perfectly fine with regular DP Alt Mode docks in Boot Camp.

Sure. But it’s like in the marketing pics even. It works over thunderbolt. And that’s what they’ve said.

I’ve had zero issues using two 27” LG 5K monitors with my M1 Max (personal) or M1 Pro (work). Expensive setup for sure, but it just works and the amount of pixels is just glorious.

I'm plugging my M1 Pro directly into a 38" LG monitor with PD (which then has USB out, gigabit Ethernet, audio, etc), which saved me a lot of trouble.

(also, what's with the weird, slow CSS transforms?)

The monitor has an ethernet port or you're using a USB-C adapter for that?

Its best to assume that Apple just wants everyone to use a single external monitor with their notebooks. Anytime you go beyond that, bad things start to happen.

I had a 2017 MacBook Pro and two 27 inch 4k monitors. I connected these through a variety of different dongles and configurations but always had a similar issue - after being in use for a while, no matter what I was doing, the system started to thermal throttle to the point of becoming unusable.

After many hours of hair pulling I discovered that using display scaling was the issue. Apparently using anything beyond the "default for display" option was taxing the GPU, which causes heat, which then heats the rest of the system to the point of it throttling the CPU. When I finally realized this I moved to using an eGPU. So basically something like 700 bucks for a Razer Core eGPU and AMD video card to function as a dock. Oh and cherry on top is the Razer Core's NIC doesn't work in macOS, Razer knows this and isn't planning on fixing it.

I was really excited about the M1 systems but I absolutely do not want to go through the hell of figuring out how to get two displays working. Particularly considering that I can't just sidestep the issue by using my eGPU since those aren't supported.

The author just figured it out and shared already, no need to figure it out!

> Its best to assume that Apple just wants everyone to use a single external monitor

It's just a matter of different products having different specs. Barring the use of workarounds:

The older Macbook Pro with the plain M1 supports one external display.

The newer Macbook Pro with the M1 Pro supports two external displays.

The newer Macbook Pro with the M1 Max supports four external displays.

>However, I ran into a number of (firmware?) compatibility issues with Thunderbolt docks and dongles that made the journey harder than anticipated.

The advertising and hype kind of masks this issue. The reality of the new Mac architecture is that it is a "gaming console" compared to a normal PC. It's hyper optimized for a specific type of use and cuts corners in implementing hardware protocols and IO because there's no need for the average apple customer. As long as you only use the M1 console how it was intended it's amazing and fast. But attempt to do anything outside the normal with it and the console's glaring hardware short-cuts come to light.

If you’re going to make claims like this, you should back them up. What hardware shortcuts were taken, specifically, and how do they relate to the topic at hand?

thats just blatantly false claims. At least document those supposed hardware short-cuts then.

The main problem is that specs nowadays have become meaningless. Thunderbolt has so many variations, same with displayport and hdmi and usb. Anything in the chain can choose to embed whatever spec in whatever way they want. Its almost impossible to predict upfront if someting will work out of the box or not, especially with things like docks and dongles.

> Thunderbolt has so many variations

Actually, Thunderbolt doesn’t, where as the others are definitely true.

Inability to boot exclusively off an external hard drive for one.

https://eclecticlight.co/2021/02/10/external-boot-disks-stil... , https://tidbits.com/2021/05/27/an-m1-mac-cant-boot-from-an-e...

This is a very common thing that all PCs can do and you'd expect a top end ($$$$) laptop to be able to do. But because of proprietary choices in the boot process M1 consoles can't.

To add another data point for anyone looking for help- I connected two Displayport monitors to my M1 macbook with a Plugable Displaylink hub. The hub I chose also has 2 HDMI ports if I ever got new monitors, plus 6 USB-A ports, an ethernet port and an audio jack.

What it doesn't do, is power your laptop. I don't believe any Displaylink hub can do that.

$159 and Plugable has other port configurations to choose from as well: https://www.amazon.com/gp/product/B08B6CZ29Q/ref=ppx_yo_dt_b...

friend of mine is running three displays off a displayLink hub on his new m1 mac pro. seems displaylink is a really good choice, at least.

My Dell D6000 does this including power

Satechi makes great products. I bought this usb-c multiport adapter and the main reason i love it is because all the other usb-c hubs have a fixed length cable attached to it that when im mobile or walking around a datacenter, they fall out. With this I can either use the short included cabled or any long usb-c cable to keep the adapter further away from my computer so it doesnt hang off the side and come loose.

https://satechi.net/products/usb-c-on-the-go-multiport-adapt...

I’m using the fully specced M1 Pro Max with the laptop screen, 6k Pro Display XDR connected directly and 2x4k Dell monitors connected via the Caldigit thunderbolt hub (HDMI). It’s working great, haven’t had any major issues, the newest M1 MacBooks are quite impressive.

Apple’s default screen management tooling is awful though so I can highly recommend SwitchResX for that.

Also have a TB4 dock from Sonnettech (3 TB4 inputs / one output), to which I have a 10Gb/s qnap tb3 adapter plugged in. (The qnap works great btw if you are on the lookout for 10Gb/s networking for your MacBook. Make sure to get the sfp+ and not the ethernet version)

I am running 2 external 27" 4k HDMI displays (LG 27UK650_600) with no problem on my M1 Macbook Pro.

I am using them either with the Macbook closed or with all three screens at the same time.

One of the monitors is connected using built in HDMI and this one works super stable.

The other is connected through Belkin adapter that I bought from Apple. It sometimes experiences problems (it shows noise) and has to be disconnected and reconnected. This usually happens only after the monitor has been turned off for the night but the laptop was on (I keep it on due to various experiments I am running).

Overall I am super happy.

I got a regular M1 and then realized it couldn't support dual monitors, so I just sold my two monitors and bought an ultra wide. It's nicer anyway.

It is possible to connect multiple screens to regular M1 Macs with DisplayLink:

https://plugable.com/blogs/news/how-to-connect-more-external...

Although my experience with DisplayLink in the past has been adapters that were buggy and caused weird issues.

DisplayLink with M1 Macs is still not working properly!

4K support isn't fully capable, and scaled display modes are not hiDPI modes.

If you have standard 2K or FHD displays, then DisplayLink is probably fine right now :-)

Bought this a few months back. Simple and cheap. Instead of complex circuitry and drivers, they just punted and connected to the two adjacent Thunderbolt ports. No regrets.

https://www.amazon.com/dp/B08BFHDST3

I've had great success with dual monitors using DisplayLink Manager, really handy little app - https://www.synaptics.com/products/displaylink-graphics/down...

I really don't like dual displays, but I will say the Dell UltraSharp U4919DW is amazing hooked to my MacBook. The 32x9 is effectively two displays and it works very well as long as you do not try to use the HDMI port. Still not sure, why.

I'm hoping someone does a true 4K version (well 2 4Ks side by side I guess)

Been using a CalDigit TS3 dock for years with Intel 13” MBPs and now a 14” M1 Pro MBP and have had no issues. I did try a 16” 2019 Intel MBP with it, and there was some issue where it would not wake the monitors when coming out of sleep - I speculated due to the dedicated gpu

While on the topic of Mac displays, is anyone aware of a method to enable or mimic the OS brightness keys/controls with a non-apple display?

That's been my main gripe so far with an external display, that and also MacOS not allowing rotation of an inbuilt display.

lunar, monitorcontrol

https://lunar.fyi/

https://github.com/MonitorControl/MonitorControl

And displaybuddy https://setapp.com/apps/displaybuddy

There are a number of github projects for both MacOS and Windows that send DCC brightness signals to monitors https://github.com/topics/brightness-control

I had persistent problems with mouse jitter on just one external monitor with the M1 Air. The problem was fixed with betterDummy. I mean, this is pretty disappointing, and wasted a lot of my time. Lucky the M1 macs are so good in every other way.

off topic but in a similar Mac and display thing. I have an LG UltraFine 5k monitor that I love. I also have two MBPs, one for work (2019) and a personal 16" M1 Max.

The monitor works great plugged directly into either machine however if I try to use any sort of DP 1.4 switch both machines will only see my 5k monitor as 4k. I've tried various cables, all of which say they are DP 1.4 certified.

Anyone in this boat with me?

it's absurd that a $2K machine is dependent on plastic dongles to do basic stuff

The material they are made of is an interesting thing to call out here. Does it offend you that this $2k machine also relies on plastic keys on its keyboard?

these ports should be part of the motherboard

OP's goal was to connect multiple monitors with one cable, so adding more ports would be of little or no use.

Not sure that's really a fair criticism of the latest MacBooks. They have an HDMI port and 3 usb-c/thunderbolt4 ports that all support display port output. The only case you need a dongle for is support multiple displays while using only one port.

He doesn't need a dongle.

You can literally just buy cheap USB-C to DP cables on Amazon that work perfectly fine.

No Dongles or Docks required.

Reply on news.ycombinator.com