mirror of
https://github.com/Abdess/retroarch_system.git
synced 2026-10-20 10:23:16 -05:00
Abdessamad Derraz
b1f20fb8e0
SheepShaver opens ROM or Mac OS ROM, decodes a CHRP-BOOT image and requires a nanokernel ID it knows. By name its entry was served the 128 KB Apple IIGS ROM, which it rejects. Mac OS ROM 1.4 is taken byte for byte from the System Folder of Apple's iMac Software Restore CD 691-2313-A (archive.org, ISO sha1 as listed). Its LZSS payload decodes to 4 MB with the NewWorld nanokernel ID, and a size floor derived from the decoder keeps the IIGS ROM out.
92 lines
4.8 KiB
YAML
92 lines
4.8 KiB
YAML
emulator: SheepShaver
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type: standalone
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core_classification: other
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source: "https://github.com/cebix/macemu"
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upstream: "https://github.com/cebix/macemu"
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profiled_date: "2026-08-08"
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source_commit: "96e512bd6376e78a2869f16dcc8a9028bce5ee72"
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core_version: "2.4"
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display_name: "Apple - Macintosh PowerPC (SheepShaver)"
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cores:
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- sheepshaver
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systems:
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- apple-macintosh
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mode: standalone
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notes: |
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PowerPC Macintosh emulator living in the macemu tree alongside Basilisk II,
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version 2.4 (version.h:24-25). Runs MacOS 7.5.2 through 9.0.4 (README.md) on
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a PCI PowerMac or NewWorld ROM image.
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ROM loading (main_unix.cpp:581-613, main_windows.cpp:329-360): the path comes
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from the "rom" prefs item (prefs_items.cpp:45). When that is empty, the file
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named ROM is opened, then the file named Mac OS ROM (main_unix.cpp:162-163,
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main_windows.cpp:58-59). Neither found raises STR_NO_ROM_FILE_ERR and
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main_unix.cpp:987 aborts startup. The filename does not select the format:
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both names go through the same decoder.
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At most ROM_SIZE = 0x400000 bytes are read (cpu_emulation.h:30). DecodeROM
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(rom_patches.cpp:148-200) accepts two forms. A read of exactly 4 MB is taken
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as a plain image and copied as is. A buffer opening on <CHRP-BOOT> is
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decompressed instead, either LZSS through the lzss-offset and lzss-size
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constants (decode_lzss, rom_patches.cpp:80) or parcel by parcel through
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parcels-offset and parcels-size (decode_parcels, rom_patches.cpp:123).
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Anything else fails, and main_unix.cpp:602-609 picks the message from the
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file size on disk: STR_ROM_SIZE_ERR when it is not 4 MB,
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STR_ROM_FILE_READ_ERR otherwise (user_strings.cpp:66-67).
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PatchROM (rom_patches.cpp:671-731), called from InitAll at main.cpp:161,
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reads the nanokernel ID at offset 0x30d064 of the decoded image and accepts
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Boot TNT, Boot Alchemy, Boot Zanzibar, Boot Gazelle, Boot Gossamer and
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NewWorld (rom_patches.cpp:682-695). Any other string raises
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STR_UNSUPPORTED_ROM_TYPE_ERR. The free space checks at
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rom_patches.cpp:698-707 and the four patch passes at rom_patches.cpp:710-713
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then rewrite the image in memory, and rom_patches.cpp:729 copies its last
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megabyte past the 4 MB mark for the 68k emulator. Nothing is checksummed:
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the ROM checksum at offset 0 is only printed by a debug build
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(rom_patches.cpp:674).
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MacOS itself and the applications live in disk images referenced by the
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disk, floppy and cdrom prefs items, supplied by the user.
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Two files are installed by the emulator's own Makefile into
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$(datadir)/SheepShaver (Makefile.in:21,162-164) and read from there:
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keycodes keycode to Mac keycode table, read only when the keycodes
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prefs item is true, which defaults to false
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(prefs_unix.cpp:117). Overridable with keycodefile.
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configure.ac:754,775 picks ../SDL/keycodes or keycodes
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according to the video backend. video_x.cpp:79,1200,
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video_sdl2.cpp:97,1231
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tunconfig script run to configure the tunN interface for ethernet.
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Overridable with etherconfig. ether_unix.cpp:108,381
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The SDL2 backend falls back to BasiliskII_keycodes in the same directory
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(video_sdl2.cpp:98,1232).
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The preferences file (.sheepshaver_prefs, prefs_unix.cpp:49, or
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SheepShaver_prefs, prefs_windows.cpp:66) and the NVRAM file
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(.sheepshaver_nvram, xpram_unix.cpp:30, or SheepShaver_nvram.dat,
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xpram_windows.cpp:31) are written by the emulator when absent. Passing a
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.sheepvm directory on the command line reads the preferences from inside it
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instead (main_unix.cpp:371-384, prefs_unix.cpp:57-69).
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files:
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- name: ROM
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aliases: ["Mac OS ROM"]
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required: true
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validation: [size, signature]
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min_size: 377670
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description: "PowerPC Macintosh ROM, 4 MB PCI PowerMac image or CHRP-BOOT Mac OS ROM"
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source_ref: "SheepShaver/src/Unix/main_unix.cpp:162-163,585-610,987, SheepShaver/src/Windows/main_windows.cpp:58-59,330-344, SheepShaver/src/rom_patches.cpp:80-120,148-200,671-707, SheepShaver/src/main.cpp:161"
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note: >
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DecodeROM takes a 4 MB read as a plain image and any shorter file only
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through the <CHRP-BOOT> header. The check every accepted image passes is
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the nanokernel ID at offset 0x30d064 of the decoded 4 MB image, which
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PatchROM matches against Boot TNT, Boot Alchemy, Boot Zanzibar, Boot
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Gazelle, Boot Gossamer and NewWorld. That bounds the size from below.
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decode_lzss turns 17 input bytes into at most 144 output bytes, so a
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stream that reaches the end of the shortest ID (0x30d06c bytes) is at
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least 377670 bytes long. A 128 KB or 256 KB file is never a SheepShaver
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ROM. The Mac OS ROM file of a Mac OS 8.5 or 8.6 System Folder is used as
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it is: its data fork is the <CHRP-BOOT> image, the resource fork carries
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only icons and version strings.
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