iMac 27" not extending desktop with second monitor

[paulodl]

Hello everybody. I have a strange problem. I recently bought a new monitor (benQ PD2700U), and wanted to use it as a second display connected to my iMac Late 2013 27. Turns out it only shows the mac image when I'm in desktop "mirroring" mode. connection using a miniDisplayport to Displayport cable.
When I select the extended monitor mode, the benQ image turns black and the message "no signal" appears on the display....
I've tried everything, and the only way I have to put the image on the second monitor is to select the mirroring mode and put the image at 60Hz.... Now that doesn't solve my problem, since I really needed to have the two monitors with different images and more space on the monitor for video editing....
I've even switched the adapter cable I was connecting between the iMac and the second monitor. All I have to do is try to connect to the monitor with an HDMI adapter.... I haven't done it yet because I am awaiting for the arrival of one that I ordered.
Does anyone have any more suggestions?
Could it be limitation of iMac and not support this monitor?
I appreciate any help.
Thanks
Paulo Lourenço

 

[Nguyen Duc Hieu]

The internal LCD is 2k or 5k resolution? I guess it's just 2k.
The external benQ is 4k.
Maybe 4k is too much load the GPU can handle. Did you get the GTX780m specs? What kind of resolution you got in mirror mode?

Below is what Apple said about the monitor support.

"Simultaneously supports full native resolution on the built-in display and up to a 30-inch display (2560 by 1600 pixels) on an external display"

So, I guess you'd need to lower the resolution of the benQ to 1080p or 1440p for extended mode.

Late 2013 iMac 27' with 4k monitor - possible?

So I'm looking to add a 4k display to my 27 inch Late 2013. If it's possible. I also am wanting to make sure it's 60GHz. On Apple's website, this is what it says. What the heck is a SST? Been searching on the internet and must be dumb, because I'm not following. Single-Stream (SST) displays...

forums.macrumors.com

 

[paulodl]

The internal LCD is 2k or 5k resolution? I guess it's just 2k.
The external benQ is 4k.
Maybe 4k is too much load the GPU can handle. Did you get the GTX780m specs? What kind of resolution you got in mirror mode?

Below is what Apple said about the monitor support.

"Simultaneously supports full native resolution on the built-in display and up to a 30-inch display (2560 by 1600 pixels) on an external display"

So, I guess you'd need to lower the resolution of the benQ to 1080p or 1440p for extended mode.

Late 2013 iMac 27' with 4k monitor - possible?

So I'm looking to add a 4k display to my 27 inch Late 2013. If it's possible. I also am wanting to make sure it's 60GHz. On Apple's website, this is what it says. What the heck is a SST? Been searching on the internet and must be dumb, because I'm not following. Single-Stream (SST) displays...

forums.macrumors.com

Thanks. Unfortunately lowering the resolution in benQ didn't work either... Fortunately, I've already been able to connect everything through the MiniDisplayport/HDMI cable. With full resolution on iMac and 4k on benQ. It seems to me that iMac and benQ don't really like being linked together by the Minidisplayport/Displayport cable (i tried 2 defferent cables)