Purpose
R4 DS can be loaded with media software and data, allowing a user to turn his Nintendo DS into a music and video player. Other home-brew apps allow players to use their machines as personal organizers or portable art studios. One of the biggest applications of R4 DS involves gaming. The cartridge can be loaded with home-brew games, emulators and ROM files for systems such as the Nintendo Entertainment System, Sega Master System and TurboGrafx 16.
Using R4 DS
R4 DS does not interface directly with your computer. Instead, the computer is used to download and organize the data, programs and files you wish to use on your Nintendo DS. These are then transferred to a MicroSD card via a USB-based MicroSD reader. Once the MicroSD has been loaded with data, it is inserted into the back of the R4 DS. The cartridge goes into Slot 1 of your Nintendo DS. R4 DS contains menu software used to navigate the applications and data loaded onto the card.
What's Included
The R4 DS cartridge is packaged with a MicroSD card reader. A protective sleeve for the MicroSD is also included. The cartridge comes with an installation CD containing software that must be added to the MicroSD card before use. A MicroSD card is not included with the device, though some retailers sell R4 DS and a MicroSD card in a money-saving bundle.
Limitations
R4 DS cannot run programs designed for Game Boy Advance. While Nintendo DS can run GBA games, these can only be booted from the Game Boy Advance cartridge slot. This means that GBA software can only be used on R4 DS with the addition of a Slot 2 device such as EZ-Flash or M3 Perfect. Some DS apps, such as "DSQuake 2," will not run without the additional memory provided by a Slot 2 device.
Legality
R4 DS is not illegal and will not void your Nintendo DS warranty. While Nintendo does not authorize or encourage the device, using it does not break any laws or perform any system-altering actions that would invalidate the console's warranty. However, Nintendo blames media cartridges like R4 DS for an increase in DS piracy, and is proactive in its efforts to combat this element. While it's possible to use R4 DS to emulate commercially available software for Nintendo DS and other systems, this is an illegal use of the device.