at 165dB

Q: macOS Sierra intermittently only detects 2nd display as 800x600 when reconnecting

At work, I've been using a mid 2014 MacBook Pro Retina 15-inch connected to two Thunderbolt Displays.  The one of Thunderbolt Displays is daisy chained to the other via thunderbolt, and I then connect to with thunderbolt.

 

Normally throughout my day I'm disconnecting and using my laptop away from my desk, but when I return to my desk, I usually use my MBP with the lid closed and just use the two Thunderbolt Displays.

 

Despite this setup historically working just fine, after an up grade to macOS Sierra 10.12 I've hit an issue when my laptop wakes up after being reconnected to the Thunderbolt Displays.

 

One display will initialize correctly at 2560x1440 but the other display will only run at 800x600.  If I try and manually adjust the resolution settings for the displays, I can only select 800x600 for the effected display.

 

The MBP has two Thunderbolt ports, and if I switch which port the pair of displays are connected two, the monitor forced to 800x600 swaps.  Either way, once the issue starts, I'm stuck with one display at an abnormal low resolution.

 

If I disconnect the two displays, power cycle them, and plug them back in, I still have the issue.

 

If I open or close the MBP's lid, the MBP's screen works at normal resolution, but I still have the issue.

 

The only workaround I've found right now is to reboot my MBP.  Then the displays work normally.

 

So far, this issue seems intermittent, but I've encountered it 4 times this week since upgrading.

Mac Book Pro, Mac OS X (10.5.2)

Posted on Sep 22, 2016 1:05 PM

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Q: macOS Sierra intermittently only detects 2nd display as 800x600 when reconnecting

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  • by AppleJen77,

    AppleJen77 AppleJen77 Sep 23, 2016 7:41 PM in response to at 165dB
    Community Specialists
    Sep 23, 2016 7:41 PM in response to at 165dB
    Hi there, hi 165dB!


    Thanks for reaching out to the â€‹Apple Support Communities! It sounds like ou are having issues running the MacBook Pro on exnternal Thunderbolt displays. Check out this article for steps to Get help with video issues on external displays connected to your Mac. It has some great steps you can try to see if you can get the second display working properly.

    Another option you can try is in this article: How to test an issue in another user account on your Mac. This will allow you to check to see if the issue is user specific or system wide.

    Regards.

  • by JimBobAmigo,

    JimBobAmigo JimBobAmigo Sep 27, 2016 12:36 PM in response to AppleJen77
    Level 1 (4 points)
    Sep 27, 2016 12:36 PM in response to AppleJen77

    Hello, thanks for this, as I am having (almost) the same problem. I actually am connecting to only one external display, not two.

     

    Unfortunately, the suggested fixes on the page you linked don't help here. It appears to be a bug introduced in Sierra. If I restart my machine, the external display most usually is properly detected as a Thunderbolt Display, and if I put the MacBook Air of mine to sleep and wake it, the display is almost always then set at a resolution of 800x600. Nothing I do seems to address the issue except for restarting and hoping for the best.

  • by at 165dB,

    at 165dB at 165dB Sep 27, 2016 4:01 PM in response to AppleJen77
    Level 1 (4 points)
    Mac OS X
    Sep 27, 2016 4:01 PM in response to AppleJen77

    Thanks for those links, I've tried all that apply to my situation, and here are the results (so far):

     

    9/27/2016 I encountered the issue again. 

    I forced my mac to sleep again, and woke it up.  Still had the display that would only allow 800x600.

    I created a new user, logged out of my current user, and logged into the new user.  Still had the issue.

     

    I then followed the steps to reset my Mac's NVRAM and SMC.  I did both before rebooting into the normal OS.

    After doing so, I was able to reset both my Thunderbolt Displays to 2560x1440.  Since then, I have not seen the issue, but this is an intermittent issue, so I'll keep and eye on things this week.

  • by at 165dB,

    at 165dB at 165dB Sep 27, 2016 4:02 PM in response to JimBobAmigo
    Level 1 (4 points)
    Mac OS X
    Sep 27, 2016 4:02 PM in response to JimBobAmigo

    You might want to try and follow the steps to reset my Mac's NVRAM and SMC.  I don't know that it fixes the issue yet, but I've not seen it happen since I did those steps Monday.

  • by JimBobAmigo,

    JimBobAmigo JimBobAmigo Sep 28, 2016 7:51 AM in response to at 165dB
    Level 1 (4 points)
    Sep 28, 2016 7:51 AM in response to at 165dB

    Thanks!

    Did reset the SMC and the NVRAM per your links, all good there. Unfortunately it looks like in my case the problem persists. For now, if I restart the machine after connecting it to the Thunderbolt Display, I can use the correct resolution for the screen from the beginning. If it sleeps, though, there is a reasonable chance it will default back to 800x600. So guess I'll be restarting for a while until this issue gets fixed.

  • by at 165dB,

    at 165dB at 165dB Sep 29, 2016 9:25 AM in response to at 165dB
    Level 1 (4 points)
    Mac OS X
    Sep 29, 2016 9:25 AM in response to at 165dB

    Unfortunately, when I got to work today, the issue occurred again.

     

    Lid closed, laptop had been sleeping all night.  I plug in the thunderbolt connector, and the second thunderbolt display in the daisy chain is stuck at 800x600.  A reboot is the only work around I've encountered.