Simearth 68K Mac Emulator10/22/2021
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 Motorola 68LC040 microprocessor. To date, Macintosh Repository served 1602155 old Mac files, totaling more than 325357.1GB Downloads last 24h 1260 : 300744.1MB.All versions of this emulator emulated the "user" subset of the 68EC040 instruction set with a 68020/68030 exception stack frame. Runs in B&W and in 16 colors mode (4-bits) Emulating this It should run fine under: Basilisk II.This emulator was theoretically capable of emulating 680x0 code faster than any real 680x0 was capable of running it. The emulator could recognise the same sequence of 680x0 code and run the previously-cached PowerPC code to avoid doing the translation again. 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.
![]() ![]() The compilers for Mac OS created such UPPs automatically when the proper macros were used, and the PowerPC system libraries contained native stubs to transparently call through to native or still-68k functions as needed. The 68k emulator then dealt with details such as presenting passed parameters in the right order for the ISA in question, as well as starting and stopping the emulator as required. From PowerPC code, this UPP could be passed to the CallUniversalProc( ) function to call it. However, it actually led to a data structure which contained a special trap instruction and flags indicating the instruction set architecture (ISA) of the called code. For 68k code, this pointer appeared to be an ordinary pointer to code and could be used as such. Simearth 68K Emulator Mac OS X Outside OfNative Mac OS X outside of Classic never used the emulator. PowerPC Macintosh emulators such as SheepShaver therefore use the emulator as well when running the classic Mac OS.
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