The PSP can operate up to a 333MHz CPU, and has a 480x272 screen, which I also thought it being four times the size of TIC-80's graphics buffer. However, lag will be more frequent than it is on more recent devices. If you'd really want to play FPS80 on your PSP, then you shat out of luck because FPS80 hogs CPU time, almost becoming unplayable under 333MHz.
I've heard that the PICO-8 requires at least 700MHz, and Voxatron requires at least 800MHz. So I suspect TIC-80 needs over 700MHz due to the better hardware specs than PICO-8.