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emulation uses far more system resources than you think. Even a high spec Mac Pro would have trouble emulating an Xbox 360 for PS3...

Plus the PSPs hardware is geared completely at gaming with a bit of multimedia. The iPhone has a much more general purpose CPU.

Edit.
I did a quick search and found this thread from the other day. https://forums.macrumors.com/threads/472433/
Goes into a bit more detail about emulation
 
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