Mac mirroring display on two external DisplayLink monitors

Phillips 276E8V appears to be a 4K display supporting Billions of colors with HDR=ON for 10 bits/color

interfaces include:

• that DisplayPort 1.2 
• HDMI 2.0 x 2

at 10 bits/color, it can firstly support up to 60 Hz in DisplayPort

at 8 bits/color, it can directly support up to 75 Hz in DisplayPort

The HDMI 2.0 port can only support up to 4K at 60 Hz.

Your Apple-silicon MacBook Pro with MAX processor can directly support up to FOUR Fully Hardware-accelerated displays.

The Mac does not support more than ONE Hardware-accelerated display on a USB-C cable.

To use more than one display on a cable on a Mac, the port, the cable, and the first device (Dock or Display) must ALL be genuine Thunderbolt.

The Apple standard for its built-in hardware-accelerated displays, makes them suitable for full-motion video for production/display of cinema-quality video with NO dropped frames, and NO dropouts or partial-blank scan lines due to memory under-runs or other issues. 

The Windows standard Is, "if YOU think its good enough, then it IS!"

There is not enough bandwidth to support two displays on one USB-C cable, DisplayLink or Not.

Sorry to disappoint, but you must have at least one Thunderbolt-capable display to use your Dell dock in a dual monitor setup with extended desktops (and if you have only one TB display, you must connect it second after the DP/HDMI display and even so, IIRC, you run into trouble when a setup like that wakes from sleep).

See this support article from Dell:

https://www.dell.com/support/kbdoc/en-us/000124312/dell-thunderbolt-dock-wd19tb-and-apple-usb-c-hosts#Dual_Monitor

My suggestion would be to get a more Mac-friendly dock. Brydge Stone Pro docks support dual 4K, as do docks from Belkin and others. Expect to pay north of $250, if you’re looking at a dock costing $60-200 you’ll get mirrored desktops.

The title of your post says DisplayLink, while the body of your post refers to the Dell WD19TBS docking station and to DisplayPort.

DisplayLink is a second-class workaround technolgy that lets you connect more monitors to a computer than its hardware supports. The Dell WD19TBS docking station is a Thunderbolt dock that, to the best of my knowledge, doesn't use it. (I've only ever heard of one that did.). There is no DisplayLink chip set in it for a driver to talk to – and thus absolutely no point in installing DisplayLink software on your Mac. That software will not do anything – other than take space and possibly keep you from viewing DRM-infested video content – if there is no matching DisplayLink chip set, no matching "stunt box", for it to talk to.

DisplayPort is the name of the hardware video standard, and what both your Mac and the Dell dock use.

The issue here is that the Dell WD19TBS has more than two video outputs. It drives some using DisplayPort MST, a DisplayPort feature which Macs do not support. Thus, depending on the pair of outputs you choose, you may be driving two displays from a single video signal that the dock is replicating. As far as the Mac is concerned, there is only one display; and as far as you are concerned, they are stuck in "mirroring" mode.

The fix is to use outputs that are connected to different video signals. See the "Dual Monitor Setup" section of Dell Support – Dell Thunderbolt Docks and Apple USB-C Hosts .

Grant Bennet-Alder wrote:

To use more than one display on a cable on a Mac, the port, the cable, and the first device (Dock or Display) must ALL be genuine Thunderbolt.

That Dell dock is a Thunderbolt dock. The issue is very likely to be the "extra" outputs and use of DisplayPort MST. While MST is part of the DisplayPort standard, it is one that Apple doesn't support.

neuroanatomist wrote:

Sorry to disappoint, but you must have at least one Thunderbolt-capable display to use your Dell dock in a dual monitor setup with extended desktops

I doubt that. I think the Dell Support article is saying that you have to make at least one of the video connections using one of the dock's Thunderbolt ports.

It is very likely that those ports support both Thunderbolt and USB-C (DisplayPort Alt Mode), which would mean that the attached displays or adapters do not need to be Thunderbolt-capable. You can get adapters to go from USB-C (DisplayPort Alt Mode) to just about anything you might need (DisplayPort, Mini DisplayPort, HDMI, etc.).

TheSimulator wrote:

> There is not enough bandwidth to support two displays on one USB-C cable, DisplayLink or Not.

Weird. I must have imagined seeing two 4K monitors being driven by a lowly Windows PC, then, while also simultaneously providing Internet access. Are you saying 40 GB/sec over USB 4 isn’t enough bandwidth?

Either way, you have not addressed the issue I raised.

I believe that Mr. Bennet-Alder is accustomed to seeing posts from people who tried to drive two monitors from a plain USB-C dock, and thought that you were using one. The Dell WDTBS19 is neither a plain USB-C dock, nor a USB4 dock, nor a DisplayLink-equipped dock. It is a Thunderbolt 3 dock.

Macs do not support DisplayPort MST daisy-chaining, or the equivalent, and most Thunderbolt docks from Mac-oriented vendors like Other World Computing, SonnetTech, and CalDigit only provide for plugging in two displays at a time. A Mac like yours is happy to drive one 5K/6K display or two 4K displays off such a Thunderbolt dock.

Your dock, and a certain HP Thunderbolt dock whose name pops up in these forums from time to time, offer more than two places to plug in displays. They get the extra outputs by essentially wiring together some outputs, using MST. This means that you need to select a pair of outputs that are NOT wired together via MST if you want a Mac to see two plugged in displays as individual displays that can be run in extended desktop mode.

My apologies to everyone.

I have answered so many queries from users who relied on the claims for the WD19 USB-C ONLY version of this Dell Docking station that I assumed this was the same sad story. "Works great on Windows, why not on my Mac?"

I read that a Dell WD19 docking station was in use, and the author said they were making a USB-C connection, and I did not 'do my homework'.

The accurate information is that there are two versions of the WD19, and the one that has a genuine ThunderBolt interface to the computer-end (prominently marked with the Thunderbolt trademark) should work, awkwardly (under certain limited circumstances already noted above) for two carefully-selected displays on one ThunderBolt cable on a Mac.

I am sorry to have made a mess of things by not being more methodical.

Now that you've called attention to it, it would appear that WD19* is a Dell brand line, not just the name of a single dock.

There are USB-C docks called WD19, WD19S, WD19DC, and WD19DCS … and Thunderbolt docks called WD19TB and WD19TBS. (Some may now be discontinued.)

One Dell site says that "The WD19 dock has three connectivity options: USB-C, dual USB-C, and Thunderbolt 3." This statement probably refers to there being several docks with the same "family name" – in which case, one might surmise that "DC" refers to "dual USB-C" and "TB" refers to "Thunderbolt".

Dell – Driver Installation Guide for Dell Docking Station WD22TB4, WD19TB, WD19DC, WD19, WD19TBS, WD19DCS, and WD19S

Dell – Driver Installation Guide for Dell Performance Docking Station WD19DC and WD19DCS

That would be good for the OP. A cable is cheaper than a new dock. The pictographs do show a TB+DP icon on at least one of the monitors.

NB>> those Dell docking station drivers are for Windows, ONLY.