SN75dp149 issue

Hello，I am HW engineer in CY Tecnology,we want to use the SN75DP149 to design a  DP to HDMI Dongle,I have apply for a SN75DP149  DEMO Board ,I am testing now,but I have found a question ,the DEMO Board can not achieve 4k\30HZ, it can only achieve 1080p on the desktop computer,but it can also achieve 4k\30hz on my apple all-in-one PC,I have design my own dongle and make 2 samples ,it is the same as the demo board.I must solve the problem now,can you help me?thanks very much

Hi Zhao

DP149 supports 4K*2K@30FPS with  8 bit color depth or

                           1920*1080@60FPS with 16 bit color resolution.

Can you check whether it is the difference of color depth caused the different performance?