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Need assistance connecting two external displays - only one works. Running through a docking station. Both externals worked through the dock via my Dell Latitude 7430 laptop, so all connections are correct.
MacBook Air 13″, macOS 15.1
neuroanatomist wrote:
murray218 wrote:
Great! I’ll try the Thunderbolt dock and report back. Thank you.
Please read what Servant of Cats wrote: “Macs that support two or more USB-C or Thunderbolt displays can often drive two displays with up to 4K resolution at 60 Hz through a Thunderbolt dock or hub.”
Your Mac doesn’t, it supports one with the lid open. If you connect a Thunderbolt dock and two displays, you’ll get two displays showing the same thing (mirrored), not separate desktops. If mirrored is what you want, a simple (and cheap) display splitter will do that. If you want separate displays, the dock won’t help. You do need to close the lid (with an external keyboard/mouse and AC power) to use two displays.
That does raise the question – how does the M3 MacBook Air handle the case of two monitors connected to a Thunderbolt dock?
Adding the Thunderbolt dock will not let you drive both displays as independent displays with the lid open. The dock gets the video signals from the Mac, and when the Mac's lid is open, there will only be one signal.
But with regards to docking, could you leave both displays plugged into the dock all the time – and just
Using the monitor power switch would be more convenient than messing around with the second monitor's cable.
Use dual monitors with your MacBook Air and MacBook Pro with M3 chip - Apple Support
murray218 wrote:
Thunderbolt is a cable, right.
No. Thunderbolt is not a cable. It is a high-speed, high-end interface. One that is optional (though common on Macs) at that.
There are certified Thunderbolt cables because you need a very high-quality cable to reliably carry Thunderbolt data between the Thunderbolt ports on two devices (such as a M3 MacBook Air and a Thunderbolt dock). Plain USB-C cables are not guaranteed to carry Thunderbolt reliably. Some of those only support carrying USB 2.0 – which runs at less than 1/80th the speed of Thunderbolt. Others are charging cables that don't carry data at all. When selecting USB-C cables, you always need to check that they are suitable for the purpose at hand.
The USB-C ports on your M3 MacBook Air are multi-function ports that can support any of the following:
depending on what you plug into them.
MacBook Air (13-inch, M3, 2024) - Tech Specs - Apple Support
Simple: close the lid of your Mac (you’ll need an external keyboard and mouse/trackpad, and power for the Mac). If you get both displays working, you’re done (that’s the only way it will work). If you don’t get both displays working, get a new dock (but you’ll still need to close the lid).
The M3 MacBook Air only supports using two external displays when the lid is closed.
In addition, Macs do not support DisplayPort MST daisy-chaining or connecting two displays through a plain USB-C dock. Macs that support two or more USB-C or Thunderbolt displays can often drive two displays with up to 4K resolution at 60 Hz through a Thunderbolt dock or hub. Thunderbolt provides a wide “data highway” that the Mac wants to see before it will provide two video signals.
murray218 wrote:
Great! I’ll try the Thunderbolt dock and report back. Thank you.
TL;DR - close your lid.
Please read what Servant of Cats wrote: “Macs that support two or more USB-C or Thunderbolt displays can often drive two displays with up to 4K resolution at 60 Hz through a Thunderbolt dock or hub.”
Your Mac doesn’t, it supports one with the lid open. If you connect a Thunderbolt dock and two displays, you’ll get two displays showing the same thing (mirrored), not separate desktops. If mirrored is what you want, a simple (and cheap) display splitter will do that. If you want separate displays, the dock won’t help. You need to close the lid (with an external keyboard/mouse and AC power) to use two displays.
Way too complicated. Thunderbolt is a cable, right. I already have a docking station, which very ably projects two displays from a Dell laptop. I’m replacing the Dell with my new MacBook Air and need a simple solution to project the same 2 displays. If the Thunderbolt cable is the answer, I’ll try it; otherwise, I’m looking for a new docking station that’s compatible with the Mac. Simple answers requested. Thank you.
murray218 wrote:
Way too complicated. Thunderbolt is a cable, right. I already have a docking station, which very ably projects two displays from a Dell laptop. I’m replacing the Dell with my new MacBook Air and need a simple solution to project the same 2 displays. If the Thunderbolt cable is the answer, I’ll try it; otherwise, I’m looking for a new docking station that’s compatible with the Mac. Simple answers requested. Thank you.
A Thunderbolt cable will not turn a plain USB-C dock into a Thunderbolt dock. I do not know what kind of Dell dock you have, but docks with multiple video outputs have various ways of providing those outputs.
Some have outputs that are not first-class hardware-supported outputs at all – outputs which only work, with compromises, if you install matching driver software on your computer. Some rely on DisplayPort MST (which Windows PCs might support, but which Macs do not, to the same extent.). Some rely on Thunderbolt.
There may even be a mixture of methods within a single dock.
Given that you chose a Mac that can only sometimes drive two external displays, I'm sorry if the answers seem complicated, but I am trying to provide as much useful information as I can without being inaccurate.
I do not have a plain M3 MacBook Air and two monitors and a Thunderbolt dock at my disposal to test things for you.
and, to add to this, I've changed the Privacy and Security setting to Always Allow Accessories to connect. Still no bueno.
Great! I’ll try the Thunderbolt dock and report back. Thank you.
Multiple displays with MacBook Air 13" (M3)
