Slow PSP games?

Has anyone had a game noticeably slow down on the psp 3001 official psx emulator? I backed up persona 2 eternal punishment to it and the gameplay was horrible when I tried Innocent Sin it worked perfectly I also had a problem like this when I backed up my brain dead 13 and it played fine to a point then it was all vndkls'airahgrio;aofjpJEFPPIR and I could only enter the menu options and exit the emulator.
So can anyone tell me how to fix these problems on the official psx emulator released for the psp by sony?