Nintendo DS vs Game Boy Advance

Anybody knows why there is gba slot in ds boxes? nintendo ds gameboy slot The first step was to figure out how the Nintendo DS talks to the Slot-2 Game Boy Advanced cartridge slot In the OCC project the nintendo switch lite cartridge slot Insert your Game Boy Advance cartridge on the bottom slot of your DS This is labeled for you next to the slot as Slot-2

nintendo ds slot 2 The DS lineup all had the option to play gameboy games, hence the gba slots in the ds cases