Nothing is impossible; such is merely the thoughts of ignorance. That is not to say that a Saturn emulator will work well or even play games at any reasonable speed. But it is certainly not impossible.
In fact, as hard as it sounds, I think some of you are complicating the issue; the Saturn's 8 processors don't handle radically different task; in fact, nearly 2 of each processor handles a similar task and the PSP has 3 processors: the CPU, GPU(forgot its real name) and ME; the coders can simply bundle the the similar processors to their PSP counter parts. For instance:
Motorola 68EC000 sound controller and Yamaha FH1 DSP sound processor would be handled by the ME.
Custom VDP 1 32-bit video display processor, Custom VDP 2 32-bit video display processor and Custom Saturn Control Unit (SCU) with DSP for geometry processing and DMA controller would be handled by the VFPU.
And obviously the 2 CPUs would be handled by the PSP's cpu, with the other 2 remaining processors handled by software.
By no means an easy task, but not impossible...
