KS8000 has a 60hz panel on all it's resolutions so most you can do is 60. There are some displays that do support 120hz at 1080p though, unfortunately the KS8000 isn't one of those.
It's weird, cause everywhere says it's a 120hz panel (it's advertised as such on the box), but it doesn't seem to accept any 120hz inputs.
Rtings says 1080p/120hz didn't work.
But then there are also many reports of 1080p/120hz working properly on it with certain graphics card configurations.