Mac mini (M4) — Windows move to one screen after sleep with dual display setup

The Mac does not rely on Windows-like side-loaded "Drivers" which are actually packages of resolutions and settings for a specific display. Instead, it goes straight to the immutable source -- it asks the display itself.

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• hold the Option key while you click on the (Detect Display) button that will appear in Displays preferences (from another display)

so try doing some of those things and see if the display comes alive.

Modern Displays with multiple ports are sometimes busy scanning the other ports, looking for an input, and miss the query from the Mac. They need to pay attention to the port you are actually using, or they will miss the query.

Some displays have On-Screen Display settings that can be used to tell the display a computer is attached on a certain port, or a certain port should be highest priority. Changing those may make your display more responsive.

Some displays include their own private "sleep" settings for the display alone. This can allow the display to enter its own sleep mode, on top of the Mac's not sending it data. A display that is sleeping on its own can generally not respond to the Mac's query, and will stay dark.

<< all open windows move to one of the screens instead of staying where they were. >>

That specific symptom occurs when the second display comes ready so late, the Mac decides it is no longer available.

In that moment, all the windows on the [assumed dead] display are moved to the nearest edge of the [still working] display, so that they will not be lost forever and inaccessible.

On an Intel system, the System Management Controller (SMC) runs stuff like fan speeds, clock rates, sleeping, waking, and charging.

On an Apple-silicon Mac, one of the efficiency processors stays slightly awake at all times doing similar work. So the concept of "asleep" makes far less sense, since it is never fully asleep.

Consider Never sleeping your Mac.

<< That’s why I think this isn’t really a “display not responding” situation. >>

This happens in only a few milliseconds at system startup, or when an App goes to draw in its window.

When a more complex App that have a lot of processing to do are ready to draw their windows, the display may be ready to go, so some Apps windows will appear where you expected.

<< using a DisplayPort-to-HDMI adapter, plus another HDMI-to-DVI adapter at the end. >>

In general. "stacking" adapters is a losing proposition. You should generally convert from computer output to desired display input in at most ONE adapter.

Which display is the slow one?

if you swap adapter stacks, does the problem follow the adapters?

Does the problem follow the displays?

<< Regarding the adapters, you’re right: I’m aware that stacking two isn’t ideal. Unfortunately, with these old monitors (DVI only) and the limited outputs on the Mac mini, it’s currently my only option. >>

There are dozens of USB-C to DVI adapter/cables available for around US$10 that would work with an M4 mini.

I tried to suggest earlier that if your second display was using ONE adapter (instead of "stacked" adapters that we know can be troublesome) I thought it would come up faster and your problem might be solved.

The folks who answer queries here are other users like you, who have decided to volunteer their time to help other users. Apple employees are generally prohibited from posting here, except for clearly-identified Apple Support Community Specialists who may post to be sure your query does not go un-answered after days.

Readers contribute when they have something to ADD to the discussion that has not already been said, or when something already said is not quite right and needs to be adjusted, or when they can elaborate on something stated, but not in enough detail. Occasionally a reader will post a summary of what has been noted to drive home the most important points.

when the answers provided are already the "best available", other readers may not have anything to add.

However, you can see how many times the post has been viewed on the 'My subscriptions" page.

ToDoApp wrote:

Thanks, Grant — seriously, you seem to be the only one in this so-called "official" Apple Community who actually replies.

I have to say, I’m honestly disappointed. Is everyone else just pretending not to see the thread, or is that part of Apple’s new “seamless user experience”?

@Grant Bennet-Alder is the contributor who is most familiar with how the external displays work with Apple's computers. Plus @Grant is able to provide those important technical details in a very clear & concise way. I have not seen any other current forum contributor post so such information on this forum regarding external displays. If I see a discussion regarding external displays where @Grant is not involved I will try to get his attention to assist since I am unable to provide the assistance even after reading so many of @Grant's posts (nor do I have the time necessary to assist which such a thread requires).

You are working with the best & most knowledgable contributor already regarding issues with external displays. You are in great hands here. Even Apple techs don't provide the level of assistance that @Grant does.