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Dynamic Recompilation Emulator

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The Dynamic Recompilation Emulator (or DR Emulator) is an extension to the current interpretive emulator providing on-the-fly translation of 680x0 instructions into PowerPC instructions for increased performance. The design of the DR Emulator mimics a hardware instruction cache and employs a variable size translation cache. Each compiled 680x0 instruction requires on average about four PowerPC instructions. In operation, the DR Emulator depends on locality of execution to make up for the extra cycles used in translating the code. The DR Emulator provides a high degree of compatibility for 680x0 code. One area where compatibility will be less than that of the current interpretive emulator is for self-modifying code that does not call the cache flushing routines. Such code also has compatibility problems on Macintosh Quadra models with the cache enabled.