External monitor connection issues

Discussion in 'MacBook Pro' started by jerryk, Jul 8, 2016.

  1. jerryk macrumors 68040

    Nov 3, 2011
    SF Bay Area

    I have a brand new 2015 Retnina 15 with dGPU. It works fine except when I connection monitors to the display ports when I bring the unit to work.

    Usually the unit in sleep with the lid closed. I insert the mini-dp cables for the monitors and the power and USB for keyboard/mouse. Most of the time the two monitors do not come up. And then when I open the lid the retina display stays black. When this happens If I can disconnect the monitors and plug them back in one at a time, waiting 5 sec in between to get monitors up. But sometimes the retrina display does not wake and I have to crash the machine by holding the power button down for 10 seconds or so.

    I have ruled out the monitors by trying it on my 2-24 Dells at home. Same issues.

    Any thoughts on what I am doing wrong?
  2. Kissmyne macrumors 6502


    Apr 21, 2015
    I would suggest waking the unit before plugging in the monitors. It is also possible that the Automatic Graphics Switching functionality is experiencing issues while waking(i.e. In sleep mode you will typically be using the iGPU, and on models equipped with a dGPU, when external displays are attached, it will force the dGPU.). You can disable this in System Preferences>Energy Saver.

    I have also had considerable success in resolving sleep/wake issues AND external monitor issues by resetting the System Management Controller(SMC) so that may be worth doing as well.. https://support.apple.com/en-us/HT201295

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