How many external monitors does the iMac 27" with 5k display support? Specs indicate just 1. Has anyone connected more than 1 monitor successfully? How many can you connect in total?
The Late 2015 iMac 5K with AMD 395X can support two external 4K (UHD) displays (at the full 3840x2160 res) with the builtin iMac display set to 5120x2880 FYI. This is the configuration that I am currently running (with 10.11.2), using two LG 27MU67 displays attached via DisplayPort-to-miniDP cables on each of the iMac's thunderbolt ports.