We're trying to get a DELL U2515H (2560 x 1440) running on a Mac Mini (late 2011). Currently it's connected with HDMI.
Unfortunately it seems like resolutions only up to 1920 x 1200 are supported using HDMI on the mac mini: HDMI port with support for up to 1920-by-1200 resolution https://support.apple.com/kb/sp632?locale=en_US
However, resolutions up to 2560x1600 are supported using Thunderbolt: Thunderbolt port with support for up to 2560-by-1600 resolution https://support.apple.com/kb/sp632?locale=en_US
So the question is: which cable should we get to get to connect the Display -> Thunderbolt?