While testing the 2018 Mac mini, the external display I used (the NEC PA271Q) worked great. Thing is, when the Mac mini went to sleep or even when booting it, it frequently did not want to light up, the NEC PA271Q showing “no signal”. I had failurs with the following connections/cards:
- Mini DisplayPort of the OWC Thunderbolt 3 Dock.
- HDMI port from the OWC Thunderbolt 3 Dual DisplayPort Adapter.
- DisplayPort from the Gigabyte Radeon RX580 video card in the OWC Mercury Helios RX 650 eGPU enclosure.
- DisplayPort from the OWC Thunderbay 6.
The Thunderbolt 3 chipset in the 2018 Mac mini is a newer generation, and my assumption was that the wakeup issues result from that chipset and/or macOS Mojave, but that’s not an assumption I could validate without other displays.
David S writes:
I’m using a 2018 Mini with dual monitors, and I have had aggravating video wakeup issues. IMO, this doesn’t seem to be just a Thunderbolt problem. I have one of my monitors hooked up via HDMI. That’s the monitor that sometimes woke up slowly, flashing on and off. Sometimes it stayed black. Two quick presses of the Mini’s power button usually brought it back, although sometimes with windows moved. (I tried the HDMI port on my Thunderbay 4 as well as on the Mini. Same results.) I also see in some old online discussion threads from 2015 (!) that some users with the wakeup issue had one monitor hooked up via mini display port. It seems like a port-independent issue. Meanwhile, my old Cinema Display monitor, hooked up via Thunderbolt, has had no problem waking up. I thought this old thread from apple discussions was interesting; it prompted me to experiment:
Could this be the explanation? It’s true that my multi-input monitor (NEC) is the one that’s been giving me the wake-up problems. So I tried something. I used the on-screen display on the NEC to change “Video Detect” from “First” to “Last.” I’m not sure what this control actually does. But I was hoping it might impact how the monitor responds to the Mac’s query. I haven’t done that much testing, but so far (two days and several sleep/wake cycles later), the whole video system seems more stable. No more blinking and flashing, no more moved windows. Interestingly, the NEC screen never goes to full black. It does go dark, but there’s a low level glow, as if some kind of backlight is still on.
MPG: the 2018 Mac mini has gone back and I cannot test this theory but maybe someone out there can.