I've got a 43X8305C connected to an Nvidia 980ti with HDMI. In Windows it says that the TV is a native 1080p TV. I can set it to 4K resolution but it seems to upscale the 1080 signal as everything is very large.
The tv is a UK model with the latest firmware.
Any idea why Windows doesn't detect it as bring 4K? Speaking to others with Samsung UHD TV's for example they are getting 3840x2160 native.