Step 2:  Once the firmware is the ps176b0_0x07.0x00.0x23 version, install SwitchResX on Mac OS X (http://www.madrau.com).

1.  Follow instructions to disable System Integrity Protection (SIP) so that u can install a custom resolution.
2.  Create a custom resolution of 3840 x 2160 at 60 Hz using the Preset “CVT-RB” and simply putting the vertical “scan rate” as 60 hz.
3.  Save this custom resolution
4.  Restart computer to install custom resolution