Dynamic recompilation works by 'recompiling' common sections of the code into faster, PowerPC-native, sequences that were locally cached. For the PCI PowerMacs, the dynamic recompilation emulator was used to boost performance. Early versions emulated it by decoding each instruction and immediately carrying out a series of equivalent PowerPC instructions. Apple developer documents indicate that the emulator provided an operating environment most closely resembling that of the Macintosh Centris 610, a system based on the 68LC040 microprocessor. Prior to Traut's arrival there, Connectix had released Speed Doubler, which included its own faster PowerPC 68k emulator that also used dynamic recompilation.Īll versions of this emulator emulated the 'user' subset of the Motorola 68EC040 instruction set with a 68020/68030 exception stack frame. A newer version, which used dynamic recompilation for improved performance, was developed by Eric Traut, who later worked on successful emulation projects at Connectix such as Virtual Game Station and Virtual PC.
The first version was written by Gary Davidian, who had originally created it for use on the Motorola 88000 CPU, used in Apple's abortive first attempt at a RISC target platform.
