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On a brand new mid-2013 MacBook Air, with an external monitor ASUS PB278Q 27" 5ms WQHD (2560 x 1440), connected through a miniDP-to-DP cable, every time the computer gets back from the monitor sleep, the login screen has a delay of several seconds, prior to the typing or the updates being reflected.

This generally happens about a second or two after MBA's own monitor gets online, and the unresponsiveness continues for a couple of seconds, until the external monitor appears online.

Why do I have such a big screen delay on login, and how do I deal with it?

My conjecture of the situation is that when my Mac instructs the monitor that it is no longer needed, it enters some kind of power saving mode which seemingly makes it unintentionally treated as a disconnect from the Mac, and then when the Mac wakes the monitors back up, the external monitor is made to appear as a new device, and takes some extra time for configuration / adjustments. In any event, I'm convinced this should not be happening, but who exactly is to blame, and is there any way to deal with this?

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your conjecturer seems correct, when the monitor goes to sleep it is "disconnected" from the mac. When it comes back on line the Mac is waiting from EDID information to be passed explaining the monitors capabilities. it could be that the monitor is taking too long for this information to be passed to the OS. one fix for such an issue is to use a Hardware device such as a DVI Detective. This will make it seem like the monitor has never been disconnected even though it may be sleeping. and the Display driver should correctly send a valid signal to the display. –  hoss Jul 28 '13 at 13:51
    
@hoss, so, is the monitor defective by design? or is it a bug of OS X? or a combination of both? this monitor wouldn't work on single-link DVI, as it is above 1920x1200 resolution. –  cnst Jul 29 '13 at 16:33
    
Not sure, perhaps a little from column a and b. I have the same issue with my Dell 2408, 2410 and 2412s, though it's not consistent. –  hoss Jul 29 '13 at 16:40
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2 Answers 2

A new conjecture is that this is due to a non-compliant mini-DisplayPort to DisplayPort cable that is causing the problem.

http://support.apple.com/kb/TS3533

In certain circumstances you may notice a black screen after waking your computer from sleep. The computer may also appear to be unresponsive when the black screen appears.
Certain cables advertised as being VESA 1.1a compliant may contain a construction issue that may result in the DisplayPort power pins at either end of the cable shorting together. VESA 1.1a compliant cables must isolate the DisplayPort power pins at either end of the cable.

Supposedly, this only affects resolutions above 1920x1200, e.g. of the popular resolutions, only 2560x1440 and above are affected.

The StarTech mDP to DP cables are not VESA compliant, and very few mDP to DP cables are actually compliant.

There's a web-site with a list of compliant cables:

http://www.displayport.org/products-database/?products_category[]=cables-connectors&products_manufacturer=

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I had the same issue - BUT: I only had this issue with a HP monitor so far. Both a Fujitsu Siemens 19" screen (1280x1024) and a Dell Inspiron 22" (1680x1050) did not have this delay when connecting and resuming the Macbook (13", 2009) from sleep. This was with a DVI cable and Apple's DVI-miniDP adapter.

When I upgraded to a rMBP15 I still had this issue, plus the Macbook would rearrange all windows to the internal screen whenever I put it to sleep (the 13" MBP didn't), which annoyed the hell out of me. So I swapped the old DVI cable used with my DVI-to-Thunderbolt adapter for a "proper" DisplayPort cable (DP-to-MiniDP) and the screen initialization delay has gone from 5..10s (!) to below 2s.

So: It might also be a monitor issue. Not just a cable or computer issue.

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