Closed Display Mode with KVM

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Closed Display Mode with KVM

I have a 2017 MacBook Pro running Big Sur 11.6. It's connected through a third-party USB-C dock which provides power, HDMI, and USB-A connections to my monitor and keybord through KVM.

The problem I'm running into is that when I switch the KVM to a different computer and then back to the Mac, the Mac is in standby mode and will not wake up without me opening the lid. This is less than ideal, because the whole point of the setup is for me to be able to save desk space by keeping the Mac closed and in a vertical stand.

Is there any configuration change I can make so the Mac will either not go to standby when I switch the KVM away or will wake when the KVM is switched back to the Mac?

Posted on Oct 24, 2021 9:03 AM

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Answer 1

Top-ranking reply

Grant Bennet-Alder

Level 10

143,699 points

Oct 25, 2021 9:37 AM in response to StanDev

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

• on invoking Option-(Detect Display) button 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 cannot respond to the Mac's query, and will stay dark.

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Answer 2

Oct 25, 2021 9:32 AM in response to StanDev

Hi StanDev,

Thanks for reaching out to Apple Support Communities. It sounds like you have a question about standby and sleep modes on your MacBook Pro. We're happy to provide some information to get you in the right direction.

You can check out the "wake for" options with the guide here: Share your Mac resources when it’s in sleep

We also recommend viewing your sleep and wake options here: Set sleep and wake settings for your Mac

Additionally, you can find information about connected devices in the guide here: If your Mac won’t go to or stay in sleep

Specifically the section that states:

"Connected storage and devices: Malfunctioning USB and Thunderbolt storage and devices may keep your Mac from going to sleep. Disconnect those devices and see if your Mac goes to sleep. If it does, reconnect each item, one at a time, until you find the one that’s malfunctioning. Contact that device’s manufacturer for more information."

However, you should reach out to the KVM manufacture to further assist with any options to help keep the connection to stop standby after switching to a different computer. Contact a third-party vendor

Best.

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Answer 3

Oct 29, 2021 5:27 PM in response to StanDev

I never said this was a "problem" I believe this is operating as designed, but you do not yet fully understand how Apple intended it to work.

Windows and Linux use the brute force method of configuring diplays -- you manually enter the resolution you want, and it blasts out a signal whether a display is present or not. The Mac is much more subtle, and requires the display to respond to a query with its capabilities. No response yields no picture.

When the KVM is talking to a different computer, no response can be sent to the Mac (unless perhaps your KVM bridges EDID output to all computers).

The default behavior when closing the display is sleep. You only only enter 'closed display Mode' when you have power, keyboard, mouse, and external display present. If you shut off any of those, (such as by essentially disconnecting the display by switching the KVM to a different computer) you get sleep.

I suggest that if you left the Mac open, this would behave as expected and not be difficult to wake from sleep.

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Answer 4

StanDev Author

Level 1

33 points

Oct 29, 2021 5:08 PM in response to Grant Bennet-Alder

This seems very unlikely to be a display or KVM problem, because it is only experienced on the Mac. Windows and Linux systems on the same configuration do not have similar problems, and I don't believe it's a problem related to sending data from the Mac to the display--the Mac is just refusing to wake from sleep when the clamshell is closed, even if a monitor is connected via KVM.

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Answer 5

Oct 29, 2021 7:21 PM in response to StanDev

I know this is a divergent thought, but does "wake for Network access" do anything for you?

You would need a sleep proxy device, but there are simple ones.

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Answer 6

StanDev Author

Level 1

33 points

Oct 29, 2021 5:10 PM in response to OrigamiFan1

The problem is not the Mac failing to go to sleep, it is going to sleep and staying asleep when I don't want it to. "Wake for keyboard activity" doesn't seem to be an available setting, and none of those articles were useful.

As I mentioned in my other reply, this doesn't appear to be a display or KVM problem because they both work fine for both Windows and Linux computers attached to the same hardware in the same configuration. This is a Mac-specific problem.

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Answer 7

StanDev Author

Level 1

33 points

Oct 29, 2021 5:35 PM in response to Grant Bennet-Alder

I understand that I wouldn't have a problem with Closed Display Mode if I didn't use Closed Display Mode. I understand that removing a monitor from a Mac in Closed Display Mode causes it to go to sleep. That is inconvenient, but would ultimately be fine if it were possible to wake the Mac after reconnecting the display.

Based on how my desk is set up, it is not reasonable to leave the Mac display open. To be honest, it is probably more practical to stop using Mac OS than try to get a different desk at this point--I'd just rather not do that if there is a way to address this problem.

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Answer 8

StanDev Author

Level 1

33 points

Oct 30, 2021 7:03 AM in response to Grant Bennet-Alder

I'm not sure if it would help or not. The problem is not other devices on the network needing to communicate with the Mac, it's that when I switch the KVM back to controlling the Mac it doesn't wake up without me opening the lid.

Looking at sleep proxy devices, it seems like it involves triggering some sort of script to tell the Mac to wake up. I could potentially build a "remote wake-up button" out of a Raspberry Pi or something, and then hit that button every time I flip the KVM back to the Mac, but that seems really antithetical to the idea of "just works."

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Answer 9

StanDev Author

Level 1

33 points

Oct 30, 2021 7:15 AM in response to Grant Bennet-Alder

I have an AppleTV and several iOS devices on the network, but it's not immediately obvious how I would use them to wake the Mac without involving a lot of hoop-jumping to try to access shared library content. I haven't seen documentation of what the wake-up packet looks like, but if you have an example of one I could probably make a Windows PowerShell script to wake the Mac on command.

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Answer 10

Oct 30, 2021 8:13 AM in response to StanDev

The sleep proxy helps you determine the IP address (and M.A.C. address) of the device.

here is an article that turned up is a quick search:

https://www.nextofwindows.com/how-to-wake-wol-windows-with-mac-and-vice-versa

.

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Answer 11

StanDev Author

Level 1

33 points

Oct 30, 2021 9:28 AM in response to StanDev

Disregard, I found a how-to for PowerShell and that seems to be working. It's definitely not ideal, but I think it's a good-enough workaround for now. There is no need for a sleep proxy because I can determine the MAC address prior to writing the script.

Thanks for the recommendation.

https://www.pdq.com/blog/wake-on-lan-wol-magic-packet-powershell/

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Answer 12

StanDev Author

Level 1

33 points

Oct 30, 2021 8:27 AM in response to Grant Bennet-Alder

That article references two utilities which aren't under active development and says I should send a "magic WOL packet" with no technical information as to what that packet looks like.

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Answer 13

Oct 30, 2021 7:12 AM in response to StanDev

several Apple devices can serve as a sleep proxy, including AppleTV device and Apple Routers.

or you can just run a little Utility on any other device on your network to deliberately send a wake-up packet to the sleeping Mac IP address and skip the sleep proxy.

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Closed Display Mode with KVM

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