iMac 27 Retina external monitor

[MisterOL]

I have new iMac with Retina display. I connected an external monitor monitor, Acer S277HK. It works fine once it starts up but the computer and monitor take 5 to 10 minutes to start. Can anyone help me?

 

[keysofanxiety]

I have new iMac with Retina display. I connected an external monitor monitor, Acer S277HK. It works fine once it starts up but the computer and monitor take 5 to 10 minutes to start. Can anyone help me?

Is it just a white screen for ages when it starts up? If so, hold CMD + ALT + P + R on startup until you hear the Apple boot chime 3 times, then let go.

 

[MisterOL]

It's a black screen and both the computer's monitor and the external monitor with one the mouse showing.

 

[MisterOL]

Anybody have any ideas?

 

[MC6800]

Does it boot fast (and/or not black screen) when the Acer isn't connected?
What happens when you plug in that display after it has booted?

 

[MisterOL]

It boots fast when it is not connected and the monitor starts up when I plug it in.

 

[MC6800]

This thread looks a similar problem with the same monitor when using a mini DP to HDMI cable. Have you tried mini DP to DP?

 

[MisterOL]

Right now I am using DP to mini DP. I have tried all the cords. I don't know why this is happening.

 

[MC6800]

A black screen suggests that the cable isn't quite able to handle the screen resolution. When it finally displays, is it at the full 3840x2560 at 60 Hz? Does it work OK at lower resolution/rate settings?

Also, what do you see first after that 5-10 min delay, on each screen? Is it still in the process of booting?

 

[MisterOL]

A black screen suggests that the cable isn't quite able to handle the screen resolution. When it finally displays, is it at the full 3840x2560 at 60 Hz? Does it work OK at lower resolution/rate settings?

Also, what do you see first after that 5-10 min delay, on each screen? Is it still in the process of booting?

It's goes to 3840x2160 but I prefer it at 2560x1440. How do I get the Hz rate?

It works fine once it on.

 

[MC6800]

It's goes to 3840x2160 but I prefer it at 2560x1440. How do I get the Hz rate?

It works fine once it on.

See About This Mac > System Report > Graphics/Displays. It should have the Hz there, but may not for that display. At any rate (so to speak), the important part is if the problem goes away at a lower resolution setting, which it sounds as though it doesn't.

What exactly do you see first after that 5-10 min delay, on each screen? Is it still in the process of booting?

Doing a Verbose Boot may be a good next step (hold Cmd-V during the power-on chime).

 

[MisterOL]

See About This Mac > System Report > Graphics/Displays. It should have the Hz there, but may not for that display. At any rate (so to speak), the important part is if the problem goes away at a lower resolution setting, which it sounds as though it doesn't.

What exactly do you see first after that 5-10 min delay, on each screen? Is it still in the process of booting?

Doing a Verbose Boot may be a good next step (hold Cmd-V during the power-on chime).

I see a black screen with a mouse that move on both black screens. After about 5 min I move the mouse and it on.

I display part told me it's going at 60 hz.