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Monitor settings disappear on daisy chained monitors

I have 2 4K BenQ PD2720U Thunderbolt 3 monitors daisy-chained to my 16" MacBook Pro running MacOS 11.2.3


Every time I disconnect/reconnect my MacBook or reboot it the monitor settings disappear and I can't seem to get them restored without hours of randomly connecting/reconnecting the monitors in different sequences.


I have set the resolution on both monitors to "Scaled" at 2560x1440 for the best mix of readability and real estate for my work. I have the laptop screen open as a 3rd monitor with the default resolution set.


After a reboot/reconnect one or both of the external monitors comes back as a 1080p display. If I set the resolution to default it's 1080 .. if I select scaled I only see 1600x900, 1080p, and 720p as options .. option+scaled shows a few more resolutions but none higher than 1600x900.


Sometimes the problem occurs on only one monitor and it could be the first or second monitor in the chain. Sometimes both monitors come back on with invalid settings.


I try Detect Displays, unplugging the Thunderbolt cable from the laptop, unplugging the daisy-chain cable, powering off the monitors in different order with different resolutions set (e.g. change all monitors to default before shutting off or disconnecting). Sometimes the monitor with the problem corrects itself only to find the other monitor now set to 1080.


Then magically after the umpteenth attempt, both monitors show up happy and I can get on with my day.


This is getting beyond frustrating as it literally can take an hour or more each time I reconnect the laptop to get my displays back the way I want them.


Screenshot below of the Display settings when the problem occurs.


Help!



Posted on Mar 19, 2021 8:03 AM

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Posted on Mar 19, 2021 8:05 AM

martinfromwestford wrote:

I have 2 4K BenQ PD2720U Thunderbolt 3 monitors daisy-chained to my 16" MacBook Pro running MacOS 11.2.3

Every time I disconnect/reconnect my MacBook or reboot it the monitor settings disappear and I can't seem to get them restored without hours of randomly connecting/reconnecting the monitors in different sequences.




Connect the displays directly to the Mac.

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Question marked as Top-ranking reply

Mar 19, 2021 8:05 AM in response to martinfromwestford

martinfromwestford wrote:

I have 2 4K BenQ PD2720U Thunderbolt 3 monitors daisy-chained to my 16" MacBook Pro running MacOS 11.2.3

Every time I disconnect/reconnect my MacBook or reboot it the monitor settings disappear and I can't seem to get them restored without hours of randomly connecting/reconnecting the monitors in different sequences.




Connect the displays directly to the Mac.

Mar 19, 2021 10:19 AM in response to leroydouglas

Not the point of buying monitors that can be daisy-chained.


I know MacOS has lacked MST support for DisplayPort 1.4 connections, which is one reason I specifically bought Thunderbolt 3 monitors for the new MacBook. I want a single display connector to the MacBook. There are a ton of 4K monitors that support HDMI and/or DisplayPort but few options for Thunderbolt 3. When BenQ released their latest monitors with Thunderbolt 3 support, I paid the premium to gain support for the latest technology and "future proof" my setup.


The only other cable I have connected to the laptop is an OWC hub that happens to include 2 DisplayPort connections for multiple monitor setups ... but again, that's not the point of TB3 ... plus I want that hub on the 2nd TB3 bus to separate 4K video input from the displays so I don't run into limits on the single bus.


When the monitor settings finally return to normal, it works just fine so it's not a problem in the link itself. This seems to be a problem with the OS "remembering" the monitor settings for different configurations and/or properly detecting the display. Perhaps due to timing in the way the monitors appear through the daisy-chained connection.


If I had a reliable, consistent method to restore the settings - even if that meant deleting a prefs file or a CLI command/script (or if 'Detect Displays' actually detected the display properly) - I would be happy with that as a workaround until Apple can figure out how to consistently detect daisy-chained monitors over TB3. Randomly resetting connections and crossing my fingers isn't a plan and falling back to dual connections means I'm paying for technology I can't use.

Monitor settings disappear on daisy chained monitors

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