Mac OS - PowerPC Emulation

PowerPC Emulation

At the time of 68000-emulator development, PowerPC support was difficult to justify not only due to the emulation code itself but also the anticipated wide performance overhead of an emulated PowerPC architecture vs. a real PowerPC based Mac. This would later prove correct with the start of the PearPC project even years later despite the availability of 7th & 8th generation x86 processors employing similar architecture paradigms present in the PowerPC. Many application developers were also creating and releasing both 68000 Classic and PowerPC versions concurrently helping to negate the need for PowerPC emulation. PowerPC Mac users who could technically run either obviously chose the faster PowerPC applications. Soon Apple was no longer selling 68000-based Macs and the existing installed base started to quickly evaporate. Despite the eventual excellent 68000-emulation technology available they proved never to be even a minor threat to real Macs due to their late arrival and immaturity even several years after the release of much more compelling PowerPC based Macs.

The PearPC emulator is capable of emulating the PowerPC processors required by newer versions of the Mac OS (like OS X). Unfortunately, it is still in the early stages and, like many emulators, tends to run much slower than a native operating system would.

During the transition from PowerPC to Intel processors, Apple realized the need to incorporate a PowerPC emulator into OS X in order to protect its customers' investments in software designed to run on the PowerPC. Apple's solution is an emulator called Rosetta. Prior to the announcement of Rosetta, industry observers assumed that any PowerPC emulator running on an x86 processor would suffer a heavy performance penalty (e.g., PearPC's slow performance). Rosetta's relatively minor performance penalty therefore took many by surprise.

Another PowerPC emulator is SheepShaver, which has been around since 1998 for BeOS on the PowerPC platform, but in 2002 was open sourced with porting efforts beginning to get it to run on other platforms. Originally it was not designed for use on x86 platforms and required an actual PowerPC processor present in the machine it was running on similar to a hypervisor. Although it provides PowerPC processor support, it can only run up to Mac OS 9.0.4 because it does not emulate a memory management unit.

Other examples include ShapeShifter (by the same programmer that conceived SheepShaver), Fusion and iFusion. The latter ran classic Mac OS with a PowerPC "coprocessor" accelerator card. Using this method has been said to equal or better the speed of a Macintosh with the same processor, especially with respect to the m68k series due to real Macs running in MMU trap mode, hampering performance.

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