SaveMii is a small dongle that is plugged into a Wii's Gamecube memory card slot. It mimicks a test interface that is believed to be used in Nintendo's own facilities (dubbed “Waikiki” by Nintendo).When the System Menu is started and such a device is found, much of the System Menu's code is skipped. Instead, the System Menu checks the validity of the disk, runs an update from the inserted disk if present, and then tries to start a diagnostic – also known “autoboot” – disk.
This will allow updates from legit Wii disks to fix the system data. Or, if the Wii's system hasn't been updated to version 3.3 yet and is equipped with a modchip, even run custom-made disks containing updates or homebrew tools to modify the system.
