i have the m3 ds real, i know it says that it is micro sdhc card 8gb compatible. My question is does it work good or not, i've heard of some trouble on other sites. or should i just go 4gb or 2gb
It works fine, as does a 16GB. Only things to remember are no more than 128 roms per folder (you can generate more folders). First folder must be NDS but after that I have Brain Games, Shooters and New. Also don't fill the card, you need to leave 1MB per 2 games as free space to let the card generate the save files, this is the minimum it is good practice to leave a little more (I generally leave 1MB per game.
