Hello, I have a Mac mini 2014 and have been using switchresx on my 4K samsung screen (U28D590D) with no issues at all. Once I upgraded to el captain I have not been able to use my display port to show 3840 X 2160 resolution at 49hz. It worked to perfection on Yosemite. I attempted to return back to Yosemite but I will lose everything since my time machine backed up everything on el captain. I'm currently also running beta version of switchresx for el captain. Does anyone know the work around on el captain to restore 4k resolution on a mac mini via display port. My monitor displays a "not optimal mode" message. Attached are the settings I'm currently using....maybe they need to be changed. I tried disabling system integrity protection and nothing, I get the same message. I appreciate the help. Is there another program like switchresx?