The SW-M001 is a cartridge from Panasoft that contains 8kB SRAM for saving game data. Its product name is PAC (Pana Amusement Cartridge). The 8kB is arbitrarily divided into 8 pages of 1024 Bytes each. A game may use one or more pages to save its data. Some games allow you to select which pages to use, others are hardcoded to use specific pages. It is up to the user to ensure he does not overwrite old save states from the game, or save states of other games. Method access to SRAM is described here. There is an option to backup save states to disk.