The specs for the R9 270 indicate that it supports 4K @ 60Hz.
It could be a defective cable.
Have you tried the new 17.5.2 driver ?
thank you very match
my driver is Radeon Software Version - 17.4.4 i do not have the new 17.5.2 driver
it is about my cable but what is mean " Current Link Settings - 5.4 Gbps x 4" if cable not work correctly.
My cable is cable expert end is specification
High-Definition Multimedia Interface (HDMI) digital audio/
video interface cable
Supports data transfer bandwidth of up to 18 Gigabits/sec
Allows bi-directional communication between smart HDMI
Supports 3D TV with video resolutions up to 4096 x 2160 at 60
Supports HDMI Ethernet Channel 100 Mbps function (HEC)
Supports Audio Return Channel technology (HARC
i now have last 17.5.2 driver but only i have 3980X2160@30Hz