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Basilisk II - RetroBIOS
Type standalone
Source https://github.com/cebix/macemu
Version 1.0
Profiled 2026-08-08
Cores basiliskii
Systems apple-macintosh, macintosh-ii
Technical notes

68k Macintosh emulator living in the macemu tree alongside SheepShaver. Emulates a Mac Classic or a Mac II series machine depending on the ROM supplied. Default model ID is 5 (Mac IIci) on a 68030 (prefs_items.cpp:88-89).

ROM loading (main_unix.cpp:681-702, main_windows.cpp:367, main_macosx.mm:431): the path comes from the "rom" prefs item (prefs_items.cpp:51) and falls back to a file named ROM in the working directory (main_unix.cpp:109). A missing or unreadable file raises STR_NO_ROM_FILE_ERR and calls QuitEmulator.

Two gates run on the image. main_unix.cpp:692 accepts only sizes of 64K, 128K, 256K, 512K or 1024K. CheckROM (rom_patches.cpp:830-842), called from InitAll at main.cpp:67, then reads the version word at ROM offset 8 and accepts 0x067c (32-bit clean Mac II, 512K/1MB) under real and direct addressing, adding 0x0276 (SE/Classic, 256K/512K) under banks addressing. configure.ac:61-68,1440-1477 defaults --enable-addressing to fastest, which resolves to real or direct, so a stock build takes 32-bit clean ROMs only. 0x0000 (Mac 128K), 0x0075 (Mac Plus) and 0x0178 (non 32-bit clean Mac II) are refused by every addressing mode. PatchROM (rom_patches.cpp:1834-1852) then rewrites the image in memory, injecting replacement .Sony, .Disk, .AppleCD and serial drivers. Nothing is checksummed: print_rom_info (rom_patches.cpp:298-310) prints the ROM header checksum without comparing it against anything.

Mac OS itself and the games live in disk images referenced by the disk, floppy and cdrom prefs items, supplied by the user.

Four files are installed by the emulator's own Makefile into $(datadir)/BasiliskII (Makefile.in:25,155-157) and read from there: keycodes X keycode to Mac keycode table, read only when the keycodes prefs item is true, which defaults to false (prefs_unix.cpp:119). Overridable with keycodefile. video_sdl2.cpp:94-97,1231, video_x.cpp:1492 BasiliskII_keycodes tried when keycodes is absent (video_sdl2.cpp:98, 1232), shipped in src/MacOSX/ fbdevices frame buffer device table, read by the X11 backend built with --enable-fbdev-dga. Overridable with fbdevicefile. video_x.cpp:1152,1186 tunconfig script run to configure the tunN interface for ethernet. Overridable with etherconfig. ether_unix.cpp:108,381

The preferences file (.basilisk_ii_prefs, prefs_unix.cpp:50) and the PRAM file (.basilisk_ii_xpram on Unix, BasiliskII_xpram.dat on Windows, xpram_unix.cpp:32, xpram_windows.cpp:33) are written by the emulator when absent.

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

ROM required in repo
Macintosh ROM image, 512 KB SE/Classic or 512 KB / 1 MB 32-bit clean Mac II

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