3 main
1)loading gba roms (psram/nor) (extra software may be needed, if or slot-1 card has no support for it) some slot-1 card has support for it)
2)use it as ds ram pack
3)use it as a ds rumble pack
extra
use for DS back-up (make you own rom)
using, Rudolph NDS back-up tool 3in1