4K display on older iMac at 30 Hz?

[Anonymous Freak]

Has anyone tried a 4K display on an older Thunderbolt-1 Mac? I know that for full 60 Hz operation, you need Thunderbolt 2 (or, more accurately, you need DisplayPort 1.2, which is part of Thunderbolt 2.) I don't care that much about refresh rate, I just want the increased resolution for photo editing on my 2011 iMac. There's a used Samsung 4K display on my local Craigslist for $200, which is a steal, but I want to make sure it will work before I buy it!

 

[omvs]

Ran 4k x 30Hz just fine on a mac mini 2011 & rMBP 2012. Used an accell active mDP -> HDMI adapter, though I know thats no longer necessary on the rMBP (not sure about the mini)

The problem cases seem to be those machines with integrated graphics -- coworkers with older intel integrated machines couldn't necessarily do 4k. I assume that iMac has discrete graphics, so expect you'd be fine given both AMD/ATI & nVidia worked with relatively old/weak chipsets.

 

[Anonymous Freak]

To answer my own question (far later, I know) in case this comes up for anyone in a search - yes.

My 2011 iMac (as well as my since-purchased 2012 Retina MacBook Pro) both support the full 4K resolution over a mini DisplayPort-to-DisplayPort cable. Only 30 Hz, but it works fine for photo editing, web browsing, etc. Even 4K videos (which are almost exclusively 30 FPS) are perfectly fine.

Of note for the Retina MacBook Pro, it even supports *TWO* 4K displays at 30 Hz - one over DisplayPort and one over HDMI (really just my one display plugged in over two cables to two of its inputs.) Apple claims its max is 2560x1440 over DisplayPort and 1920x1080 over HDMI!