External display resolution changes upon display sleep


I have a 15" MacBook Pro with Retina Display and a ShiMian QH270-IPSMS monitor (2560×1440).

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 (640×480?) 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 2560×1440 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?

Best Answer

  • 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)