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I have a macbook pro running 10.11.5 El Capitan. I have it connected to two external monitors -- one using HDMI, and the other using thunderbolt to HDMI. These two monitors are also connected to another computer using DVI cables. I'm also using the audio output jack for the macbook. When I switch the monitor to use the DVI input for the other computer, several things happen on my macbook

  1. The mouse and keyboard input freezes for about 3-5 seconds every 3-5 seconds.
  2. Video freezes intermittently, roughly corresponding with the mouse and keyboard freezes.
  3. Audio works fine without any freezes until I switch the monitor back to the HDMI input for the macbook, then it is completely muted and the volume control is greyed out until I unplug and replug in the external audio jack.

Is there a way for me to share a monitor with another computer without having these freezing problems? I would like to avoid having to disconnect and reconnect cables unnecessarily.

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2 Answers 2

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This happens on just about every computer when you are adding or subtracting output monitors. I suppose it has to do with how the(in this case internal) GPU processes the new output. 2 extra monitors is also a big feat for a Macbook's GPU!

The only way I am aware of achieving what you want would be through remote desktop. However that has it's own caveats as I'm sure you already know.

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  • They're only 1080p monitors. Macbooks pros support up to two 4K monitors -- that's like 8 1080p monitors!
    – Brendan Abel
    Jun 14, 2016 at 6:57
  • Do you know if there is a way to setup monitor "presets"? Or something where I can quickly enable/disable monitors instead of having to unplug/replug the monitors, or having to constantly re-open and reconfigure the display preferences?
    – Brendan Abel
    Jun 14, 2016 at 7:00
  • @BrendanAbel Depends more on if it is a 15" model with a dedicated GPU. It's still a lot to push on the built-in Intel GPU. Macbook Pros can support at max two 4k monitors but it will only push them to 30hz(fps).
    – David Chalifoux
    Jun 14, 2016 at 7:04
  • @BrendanAbel Here's what I've found for disabling the monitors in System Preferences: Head into your System Preferences, and from there click "Displays" from the "Hardware" section. On your primary display you should see some resolution/color options (as well as on the secondary display). Click the "Arrangement" tab at the top and toward the bottom you will see a checkbox entitled "Mirror Displays". Tick this check-box and your extended-desktop will be disabled and you can simply switch the secondary screen off. Here's the source
    – David Chalifoux
    Jun 14, 2016 at 7:07
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I'm having what appears to be the same issue - when one of the monitors is switched from DVI (Mac) to HDMI (other PC), the Mac image on the other screen (Displayport) starts freezing. I suspect this is caused by the monitor sharing a TMDS receiver between the HDMI and DVI inputs, and the macOS GPU drivers being unable to handle what the monitor does on DVI after switching to HDMI. When I switch the monitor from Mac's HDMI to something other than DVI, eg. DisplayPort input, the problem doesn't happen.

So I would suggest, if possible, to hook up the shared monitor using some other input, so that the TMDS receiver isn't shared (works for me - I only share 1 monitor, which I connected to mac with DP). If that's not an option, using a DP->HDMI/DVI adapter may or may not also fix the issue (haven't tested).

As for the audio, that's caused by macOS sound output switching to a "new" device. There's a suggestion here, but it's not ideal.

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