"Play on PC" not working Like UDK.exe ?game=MyGameETC

By the way Chosker,if we have a ¨¨heavy game¨ that works fine in editor x64.When we cook the game to x32,will it use as much ram as it needs on a x64 os windows or will it be cripled to use only 4 gb ram since it was build on x32?(and probably run low on memory?)