For gamers, modders, and preservationists, the DSi BIOS (often referred to specifically as the ) is the holy grail of the system's internal workings.
The BIOS for the ARM7 processor (handles sound, Wi-Fi, and low-level tasks). dsi bios
Once you have your files, setting them up is usually straightforward: (e.g., melonDS). For gamers, modders, and preservationists, the DSi BIOS