Dual-Cable Displays
Some displays with resolutions higher than 4K require two DisplayPort cables to connect the display at full resolution. With OS X Yosemite v10.10.3 or later, the Dell UP2715K 27-inch 5K display is supported on the following Mac computers:
Mac Pro (Late 2013)
iMac (Retina 5K, 27-inch, Late 2014)
per Apple support
https://support.apple.com/en-us/HT202856
Some displays with resolutions higher than 4K require two DisplayPort cables to connect the display at full resolution. With OS X Yosemite v10.10.3 or later, the Dell UP2715K 27-inch 5K display is supported on the following Mac computers:
Mac Pro (Late 2013)
iMac (Retina 5K, 27-inch, Late 2014)
per Apple support
https://support.apple.com/en-us/HT202856