Crisis Core FF PSP frame rate problem?

I have a PSP 3000 ver. 6.20 TN-C. I use Prometheus Iso Loader 0.1 and when i play crisis core, the frame rate is really poor, especially when in fights where there are a lot of enemies and some power surges. If anyone knows how to fix this, please help me. And BTW, the game is under .cso format.