HDMI signal splitter on M1 MacBook

Substantial_Laughter wrote:

Our church uses a Projector and two 1080p monitors to display the service (signal split into three cables) We have a 2020 MacBook Pro with an Intel CPU. Recently we had a visiting Minister set up his M1 MacBook Pro on our system and his Mac could not detect the external display signal. Is this a problem with the M1?

M1 Macs only support one external display as stated in the M1 Mac specifications.

Does anyone else ever use a Mac to connect to your projector setup?

This could be a somewhat different problem...

The Mac uses an automated system which uses the secondary data channel to the display, DDC, to query the DISPLAY for its capabilities, and sets the resolution according to what the DISPLAY reports it can attain. In this way, those pesky, error-prone humans do not get into the loop to mess up the settings.

Sometimes when using Switches, splitters, and similar devices, the device simply does not answer. When using a Mac, no answer from the device means you get no display, because none was detected.

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You MAY be able to change this by making certain that the EDID signals from one projector/display are connected through the splitter back to the input connector at the PC or Mac.

Substantial_Laughter wrote:

We use an Intel-CPU MacBook on this setup with no problems: “screen mirroring” identifies the attached 1080p signal. But the visiting Minister’s M1 MacBook could not register the splitter’s signal with screen mirroring. The splitter is powered by 9v adapter so the signal is not degraded.

See my response above and the M1 specs:

"Simultaneously supports full native resolution on the built-in display at millions of colors and:

One external display with up to 6K resolution at 60Hz"

if you can use other Macs, I withdraw my guess, and go with Bob's explanation.