[spiralpolitik]

The technical explanation is that on the base M1/M2 SoC there is one Thunderbolt bus that supports 2 display outputs.

On the MacBook Air one output is connected to the internal display leaving one output for an external display.

(The Mac Mini that uses the same SoC is limited to 2 external displays for the same reason)

To support more displays they would have to add support for a second Thunderbolt bus to the base SoC.

[richardg_]

Is this an actual hardware issue though? One issue is MacOS has never supported DisplayPort MST (Multi-Stream Transport) EVER as far as I can tell. MST allows for multiple display streams to be natively sent over a single connection for docks or daisy chaining monitors. Back on Intel Mac's if you had a dock with 2 displays or daisy chained 2 together you would get mirrored displays. The exact same Mac/displays in boot camp MST would work perfectly. 1x display per Thunderbolt 4 port is the worst!

[AlphaSite]

You can get multiple displays from a single port, the hubs are just expensive.

[daft_pink]

You can't do it with a base model M chip. Not supported on Mac unless you go with displaylink and displaylink has weird issues on mac like no hdcp support and screen recording enabled that make it a really bad experience compared to mac.

[numpad0]

There's no reason a whole Thunderbolt bus is needed for every two displays. It's just Apple's decision to build their GPU that way.

And to not support industry standard NVIDIA GPU on ARM Macs, too. 1 GPU typically supports 5 output over as little bandwidth as PCIe x1.

[chx]

Not with nVidia, no, they are 4 displays, always has been. The NVS810 8x display card is using two GM107 GPUs.

AMD is 6 displays. You see this rarely on consumer boards but the ASRock 5700 XT Taichi for some inexplicable reason did expose all six -- with four DisplayPorts to boot, too. I do not think there has been 4 DP or six output customer cards since.

[lathiat]

Even with less ports you can use Display MST hubs to breakout 3 displays from one. (But not on a Mac, even intel, they never added driver support. Works in windows boot camp though)

[numpad0]

There are couple 900-, 10-, 20-, 30-Series NVIDIA with 5 outputs. 700- and below had up to 4. IIUC it's more like up to (x px, y px) max with up to N independent clocks without external adapters or something along that.

[mciancia]

Just because there are X outputs on GPU, doesn't mean it will work with all of them at the same time

[numpad0]

I was doing 5 for no reason from a GTX970 at one point. They just work. But for some reason(segmentation?) NVIDIA brochure pages sometimes disagree or contradict with products in the market.

[lathiat]

Right, but why can't you disable the internal display to run 2 external displays? That wouldn't be an unreasonble compromise but seems not possible.

[paulmd]

M1/M2 only has 1 native HDMI pixel pipe in any form, I think? Apple uses the HDMI PHY to drive the screen on tablets, and the screen on laptops. Base-tier M1/M2 also only have a single displayport pixel pipe, and Pro/Max get +1/+2 respectively.

The base-tier chips are designed as high-volume tablet chips first and foremost, with ultramobility crossover capability.

Using DisplayLink or certain kinds of thunderbolt multimonitor are possible while running outside the pixel pipe or running multiple monitors on a single pixel pipe (this is not MST which is multiple pixel pipes on a single stream). But yeah it's ugly especially on a base-tier processor with this eating cycles/dumping heat. You're running the hardware encoder at least.

Discord had this weird error if you tried to enable the screen/audio capture, it tries to launch something and fails and the solution is you need to manually install "airfoil" because it's an audio capture module that discord licensed. you don't have to fully install it but the audio driver is the part that discord uses and that goes first (has to be allowed as a kext, ie non-secure mode). theoretically a kernel-level capture like that could be a ton faster than userland, I think that's the on-label use of airfoil.

[walterbell]

Allow the user to turn off the internal display in favor of 2 external displays. That would be a usable docked configuration.

[shanghaikid]

you are right, but apple won't do this.

[walterbell]

independent repair technician demo video to mux MBA internal and external display?