Windows pile into one monitor after dual monitors sleep

The Mac uses a single highly-parameterized Driver for every display. The parameters are set based on the reported capabilities of your display. The Mac issues a query to the display at certain times:

• wake from sleep

• Mac cable-end inserted

• when requested with Option-(Detect Displays) in System Preferences > Displays

Many multi-Input displays have a tragic flaw. The displays search round-robin through their inputs, looking for the first one that is active. If the Display is not looking at the correct input when the Mac issues its query, the request will be missed, and the Mac takes no answer as the equivalent of "no display", and that display stays dark.

If your display can be set to pay attention ONLY to the Mac attachment port, most displays (except those that are extremely slow at waking up) will always answer when the Mac sends its query, and this problem will disappear.

Hi Stephen, did you ever find a solution to this problem? I am having the exact same issue with dual monitors (2 x connected to USB-C) with my new iMac (macOS High Sierra, 2017 model, 5k Retina)

Any advise would be appreciated!

thanks 🙂

I have a Del UP2414Q as primary monitor connected via mini display port and an Asus 1080p also connect via mini displayport. Awhile ago I has similar problem and it went away. Now the only problem is that after extended display-sleep or may Power Nap the Dell will not come back on. Usually I just power off the Dell and it comes back on. Sometimes have to disconnect the video cable from the Mac to get it to com back on.

You can try resetting the SMC and PRAM.

Intel-based Macs: Resetting the System Management Controller (SMC)

About NVRAM and PRAM

all the windows on the second display get piled up into my primary display and I have to then drag everything back over.

When a display goes missing, the Mac moves the windows that were on that [non-functioning] display toward the center of the remaining extended desktop, so that at least some portion of each existing window will be visible and manipulable on a display somewhere. This is by design, and avoids having windows become lost when a display is no longer a part of your current configuration.

What you are telling me by reporting this symptom is that your second display goes missing, at least for a while, and the Mac responds as it was designed to.

To avoid this problem, your display must answer the Mac's wake-from-asleep query promptly, else be declared "absent".

It's like the new monitor is acknowledged just slightly sooner tnan my old monitor using the active connector.

If that were the case, your new monitor would simply show up a little later, with its windows still in place.

Instead, the Mac decides at some point that your new monitor is "not present" at some point during the wakeup process.

Waking up a few microseconds later gets you a picture, but the windows have already been moved off it, because the Mac decided that display was not working.

If there is a setting in your new display to focus ONLY on the port you are using for connection to your Mac, rather than hunting for an active port (and missing the query from the Mac) this problem will stop.

Since upgrading to Yosemite, I've been experiencing the same problem. After sleep mode all open windows on my second screen (30" Cinema Display) get moved to the iMac. Never had a problem before upgrading to Yosemite.

I have the same problem on my 5K iMac with two asus 21" monitors attached on Yosemite.

I am having the exact same issue. In my case, however, my mid-2012 MBPr is in a docking station with the lid closed to save desk space. I am a web developer, and typically have tons of open windows, all arranged a particular way, and it's extremely annoying to have them all snapped back up to the top left corner every time I walk away for a few minutes. My MBPr is normally in the "docked" configuration for probably 90% of the time, only being removed when I need to meet with clients, have the urge to work from the coffee shop for a change, or have some reason to travel (usually vacation). I end up having to deal with this problem too many times a day.

I agree with @Grant that the issue is most likely the "ping" request sent by the Mac, but I don't think it's due to input cycling on the monitor. My thought is that it has to do with the monitor entering "sleep" mode itself, and taking a tad longer to wake up to reply to said "ping", thus causing the issue described by @Grant. My theory stems from the fact that when this issue DOES happen for me it always has an OSD message saying the monitor is waking from sleep (and it's usually at the login prompt), but this does not happen when the MBPr screensaver is on by itself. I have dug through all the settings I could find and have not been able to find anything that allows you to turn off the sleep mode to be able to test this theory.

Have a call in to tech support I have narrowed my issue down to how spaces handles multiple monitors. Can anyone here please verify does switching from spaces all shared to different spaces for individual monitors and see if the problem occurs then? switch to individual spaces on each monitor fixes my issue but I don't want to have to switch every monitors space.

weather youre using it or not spaces is active on your Mac so it may be worthwhile to check your settings anyway if for nothing else to prove to the apple technical team that it is not a monitor issue.