PJIT vs Apple
When Apple introduced PowerPC they also introduced the idea of system-level emulation providing a stop-gap for applications (and ROM) to remain as 68K code for a while. The emulator, written originally by Gary Davidian, introduced some novel features, but wasn't terribly fast – it was a later version made by Eric Traut that introduced us to the term "Dynamic Recompiler" which would become the forerunner of Just-In-Time (JIT) Compilers. It serves as one of only two emulators which use this model.