Monitor Stays Black – Troubleshooting Sleep-Wake Lag on macOS Mojave

displaymojavesleep-wake

Since lately, I am using an AOC 32 inch monitor. A Decent piece of hardware, but alas, one thing really sucks:

  1. When I come back from a break, and screen lock kicked in
  2. I press a key on my keyboard: my older lenovo monitor immediately goes from black blank to my background image, but the AOC just sits there blank, black. For 10 seconds, 20 seconds.
  3. Most of the time, the Lenovo monitor turned black already again. When I press keys on the keyboard again, then finally the AOC tells about HDMI signal, and then shows my background image and I enter my password and log in.

In other words: there is a terrible lag before the monitor goes "alive" (10 to 20 seconds at least). Any idea anybody what I could do to change this behavior?

( for the record: both monitors are connected to my Mac Book Pro 2017 using a Lenovo ThinkPad TB3 dock, and this is not a duplicate of my own question, that one was about an external monitor never going alive )

Best Answer

That Lenovo TB3 box has 2 DP (display port) and one HDMI port:

box

( picture from here )

I simply switched ports, from DP2 to DP1, and using the first port, there is (almost) no more lag any more!

And as reference for future readers: if you intend to connect two monitors to this Lenovo TB3 dock: the second monitor has to be connected using the USB-C port on the front of the box. When you plug two monitors on the "back" of the dock, they will show the same content (like only "mirroring" is possible).

Update:

I figured a bit later that yes, switching the port did help, but only to a certain degree bit. A slightly better "solution" boils down to this:

  • when I come back, and both displays are black, I click my mouse once
  • I count to five, I hit ESC on the keyboard
  • I count to five again, and click my mouse again

What that does is: (almost) reliably get met to "both displays awake at the same time".

( I basically noticed that clicking the mouse will wake up display 1 quickly, and when putting it back to sleep with ESC, the next mouse click will wake up both displays )

Another update:

Since upgrading to Catalina, no more workarounds required. display 2 still has a lag, but I simply enter my password, display 1 turns on, display 2 follows 2, 3 seconds later. Reliably. At least for now.

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