R4 cartridge or R4 DS or other varieties such as R4 Revolution are the devices for the Nintendo DS or Nintendo DS LITE and DSI version that allow one to play games, listen to music, read books as well as explore world of other possibilities. It has the same size as that of a regular Nintendo DS cartridge. It also has a slot at the back for insertion of a micro SD card so as to allow storing music, movies and other applications such as firmware and other games according to your choice.
When one inserts a new Micro SD card into the R4 cartridge then on booting the machine one gets a menu so as to choose between games or multimedia that is stored in the SD card. After this one can also proceed to play homebrew games or other backup games or even listen to music or watch movies, all in the same Nintendo. All this is possible just by changing the card.
Below is a brief history about the R4 cards. The R4 cartridge was originally manufactured by the R4 Card team, who produced the first ever Nintendo DS R4 card in 2007. It also had a small slot at the top so as to push a Micro SD card inside. It came with a spring mechanism that would push the card into the slot, while the second push would bring out the card from its place. But this genre of R4 cards or cartridges with the spring mechanism was found to be faulty to the extent of 5%. The spring problem made the card to get damaged.
