I also have a "problem" with the PPSPP emu.
It wouldn't detect games on the external SD-card (and now that card doesn't work anymore, sigh),
so I put a game on the system (GTA vice city stories), which is a pretty big file (1,2 gig), it runs the game but it has massive slowdown.
Is this due to the fact that it takes up a lot of memory, or do I have to fiddle with the settings?