[grork]

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...

[saxonww]

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.

[szc]

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.

[lholden]

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.

[grork]

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.

[rtsao]

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/

[ubercow13]

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.

[firecall]

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! :-(

[n42]

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.

[mshaler]

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

[grork]

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.

[droopyEyelids]

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.

[grork]

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)

[jsjohnst]

> 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.

[localhost]

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.

[snlnspc]

> 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.

[alexktz]

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

[firecall]

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!