Why are you making a PS3 emulator?

Don't know exactly what a "cached interpreter" is, but someone mention that here in an old thread: http://www.emunewz.net/forum/showthread.php?tid=158608

In post #6, "Chalking Fenterbyte" mentions the same thing "cached interpreter", but AlexAltea says there's no need to improve the interpreter, and instead wish to work on the dynamic recompiler.

I also wonder what caching an interpreter means and how it improves speed supposedly.