I can also confirm that on my 3-year-old AMD Brazos laptop the HDMI is stuck at 30Hz. But on my gaming desktop with a GTX 670 the HDMI can run full res at 50Hz (this is with the included HDMI cable).
mosirisWell, the new HDMI 2.0 will do 60hz at 4k. 50hz is prolly the limitation of HDMI 1.4 which is the most current HDMI standard, HDMI 2.0 is still mostly on paper