Monitors keep switching after restart

edited March 2021 in MAIN


I have a long term installation set up, running from a brand new Mac Mini 3.0GHz Intel Core i5 6-Core Processor with Intel UHD Graphics 630 512GB Storage. I have a monitor connected to the HDMI port and two 9K NEC projectors connected to the Thunderbolt 3 / USB-C ports with HDMI adapters.

I've had some strange things happen when the system goes through it's scheduled shut down / start up sequence. I've noticed that sometimes Millumin's control window switches to one of the projectors instead of the main monitor connected to the HDMI port and then other times it stays put. You can see this when the system starts up and the Apple start up symbol shows up on one of the projectors instead of the main display. Then the Millumin admin panel goes to that monitor as well. 

I've also had a strange thing happening, where even though I save my Millumin set up with the two projectors assigned to specific sides of the two screen installation, it reverses them on start up, throwing off all of my alignment. I've checked my display preferences and that display arrangment is staying put, but for some reason, the Millumin set up keeps switching after restart.

Any help you can give would be greatly appreciated.




  • Hello @gfelice,

    Millumin uses a lot of information to retrieve the assign the right output after a startup :

    • id of the display (that may change change after a restart unfortenatly)
    • name of the display
    • size and position of the display in the desktop

    If your displays are identical (same vendor, same year of manufacturing, same serial, ...), there won't be any way to distinguinsh them except via macOS, that usually distinguinsh them based on how there are physically plugged to the computer.

    But if macOS is not dectecting the displays in the same configuration after a reboot, Millumin will have troubles to reassign displays correctly as well. An EDID emulator may be useful in this case, such as this one.

    Best. Philippe

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