why ppsspp can run MHP3HD while my psp can't

[geigermuller]

I'm not sure about that game in particular, but in general, the newer games won't work on a psp unless you upgrade it to the latest firmware, or at least, the latest one at the time the game was released. On the other hand, ppsspp doesn't have a 'firmware' of sorts, and it simply emulates the game, so it should be compatible with all games that do not have emulation issues.