The original Rumble Pak, designed for the Nintendo 64 controller, was released in April 1997 in Japan, July 1997 in North America, and October 1997 in Europe. It requires two AAA batteries and is inserted into the controller's memory cartridge slot, which prevents simultaneous use of the Controller Pak. This does not significantly affect games that feature on-cartridge save functions, but is a drawback with games that require the Controller Pak to save, as software by default was not designed to support hot swapping Paks, although some games support saving to a Controller Pak in a second controller. Nintendo remedied the situation in later games by offering developers the inclusion of special screens for hot swapping. The Rumble Pak is estimated to provide 50-60 hours of continuous rumbling before the batteries must be replaced.