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feat: collect a Mac OS ROM for SheepShaver

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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.
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Abdessamad Derraz committed 2026-10-20 03:37:57 +02:00
1 parent c07f0d9205
commit b1f20fb8e0
4 files changed
+7843 -28
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emulators/sheepshaver.yml
+14 -7
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@@ -73,12 +73,19 @@ files:
- name: ROM
aliases: ["Mac OS ROM"]
required: true
validation: [signature]
validation: [size, signature]
min_size: 377670
description: "PowerPC Macintosh ROM, 4 MB PCI PowerMac image or CHRP-BOOT Mac OS ROM"
source_ref: "SheepShaver/src/Unix/main_unix.cpp:162-163,585-593,987, SheepShaver/src/Windows/main_windows.cpp:58-59,330-344, SheepShaver/src/rom_patches.cpp:148-200,671-695, SheepShaver/src/main.cpp:161"
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"
note: >
No size is enforced on its own: DecodeROM takes a 4 MB read as a plain
image and any other length only through the <CHRP-BOOT> header. The check
every accepted image passes is the nanokernel ID at offset 0x30d064 of
the decoded 4 MB image, which PatchROM matches against Boot TNT, Boot
Alchemy, Boot Zanzibar, Boot Gazelle, Boot Gossamer and NewWorld.
DecodeROM takes a 4 MB read as a plain image and any shorter file only
through the <CHRP-BOOT> header. The check every accepted image passes is
the nanokernel ID at offset 0x30d064 of the decoded 4 MB image, which
PatchROM matches against Boot TNT, Boot Alchemy, Boot Zanzibar, Boot
Gazelle, Boot Gossamer and NewWorld. That bounds the size from below.
decode_lzss turns 17 input bytes into at most 144 output bytes, so a
stream that reaches the end of the shortest ID (0x30d06c bytes) is at
least 377670 bytes long. A 128 KB or 256 KB file is never a SheepShaver
ROM. The Mac OS ROM file of a Mac OS 8.5 or 8.6 System Folder is used as
it is: its data fork is the <CHRP-BOOT> image, the resource fork carries
only icons and version strings.