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I have a 15" MacBook Pro with Retina Display and a ShiMian QH270-IPSMS monitor (2560x1440).

The first pitfall I ran across when setting this up was that the HDMI port doesn't support my display's resolution. Instead, I am using a Monoprice Mini DisplayPort to DVI Dual Link adapter, which supports the display's full resolution at 60 Hz.

However, when my computer sleeps the displays to save power (or I press ++), and I reawaken it, suddenly my external monitor is at a very low resolution (640x480?) and the laptop's display is black. With full sleep (or ++) the problem usually does not occur, although I have seen it occur a couple times. Whenever it happens I can put the computer to sleep and wake it up again and it will most often return to the normal 2560x1440 resolution.

  • I thought it might be because the adapter is USB powered from my computer, but I plugged it into a powered external USB hub and that makes no difference.
  • I tried resetting PRAM and that didn't help either.
  • I previously installed SwitchResX when attempting to get the display's full resolution working via HDMI; this could perhaps affect what's going on, but I did fully uninstall it so I doubt it's causing problems.

Has anyone seen this behavior before, or might know what's going on or how to fix it?

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Furthermore: sometimes the external display randomly goes black for a few seconds. I think this is a separate problem but I'm not sure. –  jtbandes Nov 2 '12 at 7:45
    
Can you connect the HDMI cable and tell us which resolution you get after waking from sleep? (yes, I know you can't use native resolution with the HDMI) let us know please. –  Anonymous Nov 7 '12 at 17:23
    
@Anonymous With HDMI I can get 1080p resolution (the options are 1600x900, 720p, 1080i, and 1080p). Waking from sleep and display sleep doesn't change anything (that is, it always works) at these resolutions over HDMI. –  jtbandes Nov 7 '12 at 23:35
    
Interesting... So the problem appears to be with the adapter. Do you know someone who can give you Apple's adapter? –  Anonymous Nov 8 '12 at 8:50
    
@Anonymous Not at the moment unfortunately. What makes you think it is a problem with the adapter as opposed to my laptop or the display? If I can determine it is a problem with the adapter then I might just return it and get the Apple adapter (unfortunately more expensive). –  jtbandes Nov 8 '12 at 9:55
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4 Answers

I think it's expected behavior. The problem is that when the monitor sleeps, it is essentially being "unplugged" so the computer thinks it's gone. And when you reawaken it, the computer thinks a new monitor is being plugged in so it defaults to a supported resolution, but it's getting conflicting reports from the monitor and the DVI Link unit. Try to remove the DVI adapter and, instead, try to force your resolution using Display Maestroy (http://www.koingosw.com/products/displaymaestro.php)

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I already tried forcing the resolution with SwitchResX, and got a maximum of 2048x1152. I believe this maximum is actually a product of the hardware or Apple's HDMI software preventing me from going past ~165MHz "pixel clock". However if you know some way to force the hardware to support it that would help too. –  jtbandes Nov 7 '12 at 23:30
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I don't know exactly how the solve this problem, but if I was facing it, I would be looking at SleepWatcher to monitor sleep/wake activity, and setgetscreenres.

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I would give Caffeine a try. You can get it either from the AppStore or directly from the developer's site. It was designed to prevent your computer/display from sleeping, and might solve your problem. What's more, it's free, so the only real risk is the time it takes to install and test the application. As long as the problem is not isolated to your adapter then this could very well solve your issue.

Good luck!

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up vote 0 down vote accepted

I was able to fix the resolution-changing problem by using an official Apple adapter instead of the Monoprice one.

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