27-Inch iMac Output to 4k Display Question

[McDeth]

The company I work for is considering upgrading some of our users to dual monitor displays. All of the users that will be upgrading are currently running on either early or late model 27-inch iMacs. After a bit of research on my end (And given the ridiculous shopping request of 'aesthetics first' i.e. Brushed aluminium = good pastic display = bad) I decided upon the Samsung UD590-series of 4k Monitors. Last week I ordered a single monitor for testing purposes and today it arrived.

I eagerly hooked it up to my Late 2009 iMac and the monitor was detected, but no image displayed. I tried both the DisplayPort input and the HDMI inputs but neither was a go.

I then tried the monitor on a Late 2010 iMac with Thunderbolt ports and it worked! The only problem is that the maximum supported output resolution is only 1080P. Does anybody have experience with iMac's and 4k monitors? My gut feeling is that the video cards in these iMac's (being the default, no frills version) only support up to a certain resolution, and the 4k is above that.

Other than that I have no idea...

 

[UnknownSouljer]

High resolution monitors with 4k x 2k resolution need DisplayPort v1.2

http://www.displayport.org/faq/

DisplayPort version 1.2 was approved on December 22, 2009

http://en.wikipedia.org/wiki/Displayport

The 2009 iMac was released before the approval of DisplayPort v1.2. Whether it is compatible or not, I am uncertain. There are two factors that determine compatibility with 4k, the video card (and it's maximum resolution output, obviously), and what version of display port the video card has. HDMI has the same 'issue'. 4k resolution wasn't supported via HDMI until version 1.4, but many manufacturers don't support it. Apple on most of their products (even the newest models) don't support anything over 1080p via HDMI. Check your models to verify.

You should be able to use both the 2009 iMac and 2010 Mac Mini at resolutions lower than 4k without issue. As for your iMac not displaying anything, I would recommend checking in the System Preferences => Display and seeing if you can get it to output a lower resolution which should be possible.

 

[McDeth]

http://www.displayport.org/faq/


http://en.wikipedia.org/wiki/Displayport

The 2009 iMac was released before the approval of DisplayPort v1.2. Whether it is compatible or not, I am uncertain. There are two factors that determine compatibility with 4k, the video card (and it's maximum resolution output, obviously), and what version of display port the video card has.

You should be able to use both the 2009 iMac and 2010 Mac Mini at resolutions lower than 4k without issue. As for your iMac not displaying anything, I would recommend checking in the System Preferences => Display and seeing if you can get it to output a lower resolution which should be possible.

I tried it on a Late 2011 27-inch iMac with Thunderbolt ports and it worked, although the maximum supported res for the Samsung is still only 1080P...

 

[UnknownSouljer]

Thunderbolt 2 incorporates DisplayPort 1.2 support, which allows for video streaming to a single 4K video monitor or dual QHD monitors. Thunderbolt 2 is backwards compatible, which means that all Thunderbolt cables and connectors are compatible with Thunderbolt 1.

The first Thunderbolt 2 product for the consumer market was an ASUS motherboard, announced on August 19, 2013,[33] but the first product with Thunderbolt 2 to be released was Apple's late 2013 Retina MacBook Pro, which was released on October 22, 2013.

http://en.wikipedia.org/wiki/Thunderbolt_(interface)

This appears to be issue #2. Apple doesn't have any Thunderbolt 2 based devices other than the new Mac Pro and the latest MBPr. So it appears that 4k monitors will be useless for all of your older Macs. This is a hardware limitation. Semi disappointing that Displayport 1.2 over Thunderbolt isn't even to the latest iteration yet. Displayport 1.3 as an example supports: "32.4 Gbit/s with the new HBR3 mode featuring 8.1 Gbit/s per lane (up from 5.4 Gbit/s with HBR2 in version 1.2). This will allow 8K resolution video, at either 7680×4320 (16:9, 33.18 megapixels) or 8192×4320 (~17:9, 35.39 megapixels), two 4K streams, or 4K 3D over a single cable."

Thunderbolt 2 even with it's update doesn't have enough bandwidth to support those resolutions, let alone those resolutions and streaming that much data over the cable simultaneously. As such, and as previously mentioned, it only supports up to Displayport 1.2.

 

[McDeth]

Ah that's too bad. I was starting to wonder, since all of the reviews that I could find using the Samsung either had people using the new Mac Pros or Retina MacBooks.

Oh well, looks like I get to take this 4k monitor home with me and put it onto my gaming system for a couple of days until I have to return it

 

[HelloDude]

Hello,

Late 2009 iMac 27" (core i5 version with Radeon HD 4850 built in) can drive 4K displays fine, but only at 30Hz.

I tested mine with a Samsung U28D590D. By default only 2560x1440 will show up, but if you download SwitchResX, you can create a custom 3840x2160@30Hz resolution. The machine can even drive both the built in panel (at 2560x1440) and the 4K external display simultaneously. You can set up HiDPi mode as well on the external display to have "Retina" resolution.

30Hz is not the best, but works quite OK for videos and text. Gaming is a no-no of course (not that the 2009 iMac would be able to handle any game at these resolutions...).