How to connect two or more external displays to Apple Silicon M1 Macs

Apple’s latest range of MacBooks that use the company’s own new Silicon M1 processor cannot natively connect more than one external monitor, which is a massive limitation on the previous Intel-based generation of Mac laptops that could run two displays when connected to a USB-C or Thunderbolt 3 docking station or hub.

However, there is a workaround to run two external displays off an M1 MacBook, which we will outline here. There are some risks involved as you will be required to install third-party drivers, and these might later be unsupported by future updates of the macOS.

And you will likely have to buy at least one adapter, where previously a dock plus a display cable per external screen would have sufficed.

External displays: M1 Macs’ big problem

Apple’s new Mac mini, MacBook Air, and MacBook Pro 13in are the first Macs to feature the Apple-designed M1 CPU. They have received rave reviews for their speed improvements over Intel-based laptops, including here on Macworld.

See our comparison of the 13in MacBook Pro (M1) vs MacBook Pro (Intel) and MacBook Air (M1 Silicon) vs MacBook Air (Intel). We have also looked at the differences between the Mac mini (M1) and Mac mini (Intel).

But if your MacBook setup includes running more than one external display, you have a major problem. Apple’s M1 chip simply won’t consider it - at least natively.

While the M1 MacBooks natively support just one monitor, the M1 Mac Mini does natively support up to two external monitors - one via the HDMI port and a second via USB-C. But the latest models of the MacBook Air and MacBook Pro support only one external display.

Docking station manufacturer Plugable suggests using a combination of display technologies to get around the M1 MacBooks’ single-monitor limitation.

Its multi-display docks use a combination of native USB-C Alternate Mode (native “Alt Mode” video output) and DisplayLink technology. This combination serves as a workaround to the M1 platform supporting only a single external display via USB-C.

Note that DisplayLink requires a third-party driver to be installed on the Mac. There are different versions of the DisplayLink driver, and some bring their own compromises to the party.

Plugable UD-ULT4K dock M1 Mac

Connect M1 MacBook to more than one external display

1. First, download the latest Mac DisplayLink driver.

DisplayLink Manager Graphics Connectivity App v. 1.1.0 is compatible with macOS Catalina 10.15 and macOS 11 Big Sur. It can be managed via the DisplayLink icon in the Apple Menu bar.

Installation is straightforward, but note that this version does not support laptops’ closed-display/Clamshell mode.

Other limitations include incompatibility with display rotation.

There's an option in DisplayLink manager to “launch at startup", or you can drag the DisplayLink Manager to your Login Items in Users & Groups.


Add second screen to M1 Mac

2. Then connect the MacBook to a dock, such as the Plugable UD-ULTC4K Triple Display 4K Docking Station or the Caldigit TS3 Plus dock. Learn more about the best Thunderbolt 3 docking stations for more details, or you can connect via a simpler USB-C hub.

3. For the first screen you can connect via the dock’s DisplayPort or HDMI Port, and this will be handled natively by the M1 MacBook.

You could also connect the first external display via a Thunderbolt 3 or USB-C to HDMI or DisplayPort adapter.

The HDMI or DisplayPort output uses Alternate Mode (Alt Mode), and as it is basically a pipeline directly to the system's native GPU, it will behave just like if you hooked up a USB-C to HDMI dongle to your laptop. This requires no user driver installation.

4. Additional displays cannot be handled natively by the M1 MacBook.

You need to attach the second or third display via one or more of your dock or hub’s USB-A ports, using an adapter such as USB 3.0 to HDMI / DVI Adapter. This costs £80 or US$80, so needs to be factored in when pricing an M1 MacBook purchase if you require multiple monitors.

Another option is Plugable's USB Dual 4K Display Adapter.

This adapter turns an available USB-A 3.0 port into one DVI-I or VGA port (DVI to VGA adapter included) and one HDMI output. Each display can simultaneously support the maximum resolution of 2048x1152 at 60Hz.

Make sure to use an active HDMI DisplayLink adapter that can support 4K at 60Hz, as some are limited to 4K at 30Hz.

DisplayLink uses an installed driver and the system CPU and GPU to convert graphics data on the system into USB data packets. That USB data is then sent over the USB cable as data packets, and converted back to video information and output to the monitors via the DisplayLink chip in the docking station.

USB-A 3.0 to display adapters

Effective but unsupported

Note that neither Plugable nor Caldigit officially supports such a DisplayLink setup for Macs. The solution works, but they warn that this could become unstuck in future versions of the macOS.

Whenever there is a new OS update the drivers may need to be updated each time.

Plugable doesn't recommend the workaround for gaming, video editing, digital audio workstations (DAWs), and protected-content (HDCP) playback. For these workloads, users will want the full throughput of a "bare-metal" native GPU connection - such as provided by the DisplayPort or HDMI port on the dock using Alt Mode.

Caldigit actively recommends against using DisplayLink, as it finds it unreliable and there would be no synergy between the driver and the dock. Because it requires a third-party driver, users are at the mercy of Apple and the third-party developer to support later version.

However, this combination of display technologies does allow M1 MacBooks to run more than one external monitor, and the M1 Mac mini to run more than two.

The only risk is that it could stop working at any time, although it wouldn’t harm your system if it did.

So it’s a workaround with a potentially limited timespan but the likelihood is that compatibility would be restored at some stage if the worst happened and you would get back your multi-monitor setup.

Original Article