MacBook Pro "remembers" disconnected displays

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Level 1

46 points

MacBook Pro "remembers" disconnected displays

I use external monitors with my MacBook Pro at two different locations.

In the first location, I have two Dell P2415Q monitors that I connect via a Thunderbolt hub to my laptop. In the second location I have LG UltraFine monitor that I connect directly via Thunderbolt cable.

Ever since upgrade to Sonoma 14.6, this started happening:

Connect two Dell monitors at location one. So far so good.
Put laptop into sleep mode, disconnect monitors.
Go to second location, and connect LG monitor.
Laptop thinks it still has two Dell monitors connected when I look into either Display settings or in System Reports.
Open laptop lid... It now thinks I have LG monitor and one Dell monitor connected.
Disconnect LG monitor, it now thinks it has single Dell monitor still connected to it (FWIW, that second Dell monitor is literally 10 miles away, and most definitely not plugged into the laptop anymore).

All the windows that were on the second monitor are now inaccessible. Because there's no second monitor physically connected to the laptop.

I attempted hitting "Detect Displays" in the settings, but it does nothing. Laptop still insists there is a "phantom" Dell monitor connected to it. Reboot fixes it temporarily (until I need to move it again between two locations; and then same thing repeats). It's really a PITA to have to reboot laptop every time I connect different set of external monitors to it (i.e. move between the two locations, which is almost daily).

FWIW, laptop is 2021 MacBook Pro M1. The Sonoma 14.6.1 update didn't fix the problem. OS X versions prior to Sonoma 14.6 did not have this problem, external monitors were always correctly detected.

Are there any workarounds for this? Is this a known issue with Sonoma 14.6 that will hopefully get fixed in the future update?

Posted on Aug 13, 2024 04:51 PM

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Answer 1

Aug 14, 2024 10:24 AM in response to Alex--

Your use case is unusual, and the changes were made to retain display settings momentarily while the Mac may 'accidentally' sleep, but the user actually intended closed display mode with the SAME displays.

When you intend to change your setup, OPEN the display, then disconnect.

_______

That blocky device that plugs into the wall is the POWER ADAPTER. I am not trying to be a jerk about terminology, what these boxes do and how they do it is essential for understanding how they all work together.

The CHARGER is inside the MacBook Pro, and is completely under program control. Your Mac accepts some power when needs to run, and accepts more power when it intends to charge its internal battery. A power source like the Power Adapter can not 'force itself' on your MacBook Pro. Only the algorithms inside your Mac can decide when is a good time to charge the battery.

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Answer 2

Aug 13, 2024 06:19 PM in response to Alex--

if you KNOW you are going to disconnect displays, do so with the Mac Fully AWAKE or the Mac Shut Down.

Re-arranging of displays you do with the lid closed gets quickly entangled in 'closed display mode'.

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Answer 3

Alex-- Author

Level 1

46 points

Aug 13, 2024 07:17 PM in response to Grant Bennet-Alder

I only occasionally use the Mac with lid open (i.e with built-in display in use). Most of the time it's plugged into external monitor (or two) and with external keyboard and mouse. I usually put it into sleep mode first to make sure it is indeed in sleep mode before unplugging the cable. There were few occasions in the past where simply unplugging the cable would not result in laptop sleeping -- instead I simply found it with drained battery when I needed to use it next time.

Prior to Sonoma 14.6 update this was never a problem. It'd always figure out hardware changes (both Thunderbolt and USB devices) that occured while it was in sleep mode. Something in 14.6 update seem to have broken this...

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Answer 4

Aug 14, 2024 07:13 AM in response to Alex--

Apple wants to remember the connected displays across your shutting the lid to make closed display mode more reliable. Your Mac is not likely broken, that's just the new improved way it works now.

When you intend to change displays, you will need to open the lid during the process, else your Mac will be confused and you will get results you find unpleasant.

Don't unplug your Mac from power and leave it. Too often that results in a dead battery. if AC power is available nearby, ALWAYS plug it in. the Charger is inside the Mac, and your Mac only actually charges under program control when actually needed. Your Mac will NEVER over-charge.

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Answer 5

Alex-- Author

Level 1

46 points

Aug 14, 2024 09:04 AM in response to Grant Bennet-Alder

Grant Bennet-Alder wrote:

Apple wants to remember the connected displays across your shutting the lid to make closed display mode more reliable. Your Mac is not likely broken, that's just the new improved way it works now.

When you intend to change displays, you will need to open the lid during the process, else your Mac will be confused and you will get results you find unpleasant.

Uh... This actually makes it less reliable. It thinks disconnected display is still physically connected. Not even hitting "detect displays" in the settings will make it rescan what is actually connected to the laptop.

Don't unplug your Mac from power and leave it. Too often that results in a dead battery. if AC power is available nearby, ALWAYS plug it in. the Charger is inside the Mac, and your Mac only actually charges under program control when actually needed. Your Mac will NEVER over-charge.

It's connected to the charger 10+ hours a day. More or less the only time it's not connected to the charger is when I put it in a backpack, with battery fully charged, at the end of the day.

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MacBook Pro "remembers" disconnected displays

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