Jpcsp runs at whatever resolution you have your desktop resolution set at by default I think. If not, you can change it in the "Display" options in the configuration menu (and set it to run in fullscreen at next launch also).
As for it showing a black screen, it might be wrong settings for the game, just try switching the video options around to see what works, usually checking the game's own thread is a good idea to see what other people use to run the game. And hyakki's launcher is strongly recommended so you can manage the memory settings more easily.
As for it showing a black screen, it might be wrong settings for the game, just try switching the video options around to see what works, usually checking the game's own thread is a good idea to see what other people use to run the game. And hyakki's launcher is strongly recommended so you can manage the memory settings more easily.