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SheepShaver - RetroBIOS
Type standalone
Classification Other
Source https://github.com/cebix/macemu
Version 2.4
Profiled 2026-08-08
Cores sheepshaver
Systems apple-macintosh
Technical notes

PowerPC Macintosh emulator living in the macemu tree alongside Basilisk II, version 2.4 (version.h:24-25). Runs MacOS 7.5.2 through 9.0.4 (README.md) on a PCI PowerMac or NewWorld ROM image.

ROM loading (main_unix.cpp:581-613, main_windows.cpp:329-360): the path comes from the "rom" prefs item (prefs_items.cpp:45). When that is empty, the file named ROM is opened, then the file named Mac OS ROM (main_unix.cpp:162-163, main_windows.cpp:58-59). Neither found raises STR_NO_ROM_FILE_ERR and main_unix.cpp:987 aborts startup. The filename does not select the format: both names go through the same decoder.

At most ROM_SIZE = 0x400000 bytes are read (cpu_emulation.h:30). DecodeROM (rom_patches.cpp:148-200) accepts two forms. A read of exactly 4 MB is taken as a plain image and copied as is. A buffer opening on is decompressed instead, either LZSS through the lzss-offset and lzss-size constants (decode_lzss, rom_patches.cpp:80) or parcel by parcel through parcels-offset and parcels-size (decode_parcels, rom_patches.cpp:123). Anything else fails, and main_unix.cpp:602-609 picks the message from the file size on disk: STR_ROM_SIZE_ERR when it is not 4 MB, STR_ROM_FILE_READ_ERR otherwise (user_strings.cpp:66-67).

PatchROM (rom_patches.cpp:671-731), called from InitAll at main.cpp:161, reads the nanokernel ID at offset 0x30d064 of the decoded image and accepts Boot TNT, Boot Alchemy, Boot Zanzibar, Boot Gazelle, Boot Gossamer and NewWorld (rom_patches.cpp:682-695). Any other string raises STR_UNSUPPORTED_ROM_TYPE_ERR. The free space checks at rom_patches.cpp:698-707 and the four patch passes at rom_patches.cpp:710-713 then rewrite the image in memory, and rom_patches.cpp:729 copies its last megabyte past the 4 MB mark for the 68k emulator. Nothing is checksummed: the ROM checksum at offset 0 is only printed by a debug build (rom_patches.cpp:674).

MacOS itself and the applications live in disk images referenced by the disk, floppy and cdrom prefs items, supplied by the user.

Two files are installed by the emulator's own Makefile into $(datadir)/SheepShaver (Makefile.in:21,162-164) and read from there: keycodes keycode to Mac keycode table, read only when the keycodes prefs item is true, which defaults to false (prefs_unix.cpp:117). Overridable with keycodefile. configure.ac:754,775 picks ../SDL/keycodes or keycodes according to the video backend. video_x.cpp:79,1200, video_sdl2.cpp:97,1231 tunconfig script run to configure the tunN interface for ethernet. Overridable with etherconfig. ether_unix.cpp:108,381 The SDL2 backend falls back to BasiliskII_keycodes in the same directory (video_sdl2.cpp:98,1232).

The preferences file (.sheepshaver_prefs, prefs_unix.cpp:49; SheepShaver_prefs, prefs_windows.cpp:66) and the NVRAM file (.sheepshaver_nvram, xpram_unix.cpp:30; SheepShaver_nvram.dat, xpram_windows.cpp:31) are written by the emulator when absent. Passing a .sheepvm directory on the command line reads the preferences from inside it instead (main_unix.cpp:371-384, prefs_unix.cpp:57-69).

1 files | 1 required, 0 optional | 1 in repo, 0 missing

ROM required in repo
PowerPC Macintosh ROM, 4 MB PCI PowerMac image or CHRP-BOOT Mac OS ROM

Generated on 2026-08-23T16:12:06Z