There's one emulator that can emulate FF III at a close-to-perfect speed in the first dungeon, but some parts of the character models don't show up, the first boss and the world map lags noticably and you can't save. =/ Such a shame, for otherwise, no$gba would be the best DS emulator in existence up until now. Even the random encounters go pretty smooth. At least the music doesn't lag, except in the boss.

I don't know which one you are using, Sephiroth1999AD?