Saving to memorycard doesn't work on the gamecube.
Jordi Vilalta Prat
Memory cards are very limited, it's not a full fledged filesystems and has to be implemented specifically.
Besides, you need a SD gecko anyway to load runtime files and games off it. Well, DVD support is an alternative, but I don't see the point in this when SD gecko is:
a) common, widespread and well tested
b) cheap to make yourself of buy
c) most other GC hombrew require it