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Option is -N or --ndev. NOTE: Only seems to work with Wii images at the moment. NDEV displays the disc information from GameCube images, but then hangs. Tested with SL and DL discs on the apploader. doc/sdk_header.md: Initial SDK header documentation.
40 lines
1.7 KiB
Markdown
40 lines
1.7 KiB
Markdown
# GCM SDK Headers
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This document is Copyright (C) 2018 by David Korth.<br>
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Licensed under the GNU Free Documentation License v1.3.
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GCM images produced by the official GameCube and Wii SDKs have a 32 KB header.
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This header isn't present in images ripped using e.g. CleanRip, and it isn't
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recognized by the Dolphin emulator. It's also not present on RVT-H Reader HDDs.
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However, it **is** needed when using the official SDK tools, e.g. rvtwriter and
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the NDEV optical drive emulator.
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## Example Header
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The following header is from an swupdate image from one of the Wii SDKs:
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```
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00000000 ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
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00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
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*
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00000820 00 00 00 00 00 00 00 00 00 00 00 00 00 00 e0 06 |................|
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00000830 00 00 6b 4f 00 00 00 00 00 00 00 00 00 00 00 00 |..kO............|
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00000840 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 |................|
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00000850 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
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*
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00008000 52 41 42 41 30 31 00 00 00 00 00 00 00 00 00 00 |RABA01..........|
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```
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The header is mostly zeroes, except for these important DWORD values:
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* 0x0000: `FF FF 00 00`
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* 0x082C: `00 00 E0 06`
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* 0x0830: `00 00 6B 4F`
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The value at 0x0830 appears to be a checksum of some sort. If this header is
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prepended as-is to any generic Wii image and loaded onto an NDEV using ODEM,
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the NDEV will show a "Wrong disk" error. However, zeroing out this DWORD gets
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it working for all discs.
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Images built using `makeGCM` from the GameCube SDK always have a checksum of
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`0xAB0B`; however, the NDEV system locks up after displaying the disc info.
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