In order to enable a 3 column live tile home screen on your Samsung ATIV S, all you need to do is to go to HKEY_LOCAL_MACHINES\Software \ Microsoft \ Shell \ OEM \ Start and change ScreenSize to 1, ensuring that the home screen on your Samsung ATIV S would end up looking like the Nokia Lumia 1520 which is on the verge of a release. For additional detail that would be able to shed more light as well as insight into this particular hack, it would bode you well to head on over to the XDA Developers forum.
Oh yeah, I am also quite sure that you might also want to check out the custom ROM for the Samsung ATIV S while you are at it.