Taken from TFT Central...
One of the most interesting features of the X34 is the overclockable refresh rate. The panel itself is designed to run at 60Hz by LG.Display and that's the native refresh rate you will be able to select in Windows when you first connect the screen. However, there is a specific feature available in the OSD menu in the 'setting' section for "over clock". This allows you to enable the higher refresh rate support.