CPU doesn't mean everything. On the PSP, the CPU is used mostly for Hardware controlling and game engine processing (events, triggers, AIs). And audio goes by the SPU (i think PSP has one, correct me if it's wrong).
So, unlike the dingoo, the CPU of the PSP handles MANY LESS things than the dingoo one.
And the GPU takes care of the rest.
(Also, the PS2 CPU (EmotionEngine) comes with another internal unit designed to do graphics (basically handles Post FX and vectors, if i'm not wrong) besides the CPU. The XBOX did this separately.)
I might be wrong about a few things i said here, feel free to correct me in case.