Ocarina of Time

The Legend of Zelda - Ocarina of Time is not a rebooter game unlike most games with 64DD support. Instead it implements 64DD hooks into the game's code for specific uses.

Technical Details

• The game checks for the following 64DD units:
  • Japanese Retail Unit (Japan)
  • American Retail Unit (USA)
  • Development Unit (All)
• The game checks for the following Game Codes, regardless of region:
  • EZLJ
  • EZLE
• The European PAL version of the game does contain 64DD code, but it has been completely disabled.
  • If it was enabled, the game would check for Game Code EZLP.
  • There is no European 64DD initialization function, only the Japanese & American ones. It is unknown what initialization the game would have used.
• The game performs the following when an Expansion Disk is detected:
  • "Disk" is mentioned on the Title Screen.
  • You cannot play or create a regular save file, only Disk save files.
  • When you start up a Disk save file...
    • The way the game handles disk loading is different from other games, as it uses a byte address, and calculates the address starting from LBA 1.
    • Load 0x118 bytes from disk address 0x1060.
      The format is the following:

      SSSSSSSS EEEEEEEE DDDDDDDD FFFFFFFF RRRRRRRR
      
      SSSSSSSS = Disk Source Address Start
      EEEEEEEE = Disk Source Address End
      DDDDDDDD = RAM Destination Address Start
      FFFFFFFF = RAM Destination Address End
      RRRRRRRR = RAM Pointer to Disk Hook Function Callbacks
      

    • The game loads from Disk Source Address Start to End, to the RAM Destination.
    • Execute the initial Disk Hook Callback (ID 0), with access to required basic functions passed as argument.
    • From there, depending on the implementation on the disk side, it can replace specific files.
      It can replace the scene list, scenes, rooms, dungeon minimaps, entrance cutscenes, text.
      • There is a way to replace almost every file, but because of differences between revisions of the game, it is not reliable from a development standpoint.
      • By the exception of scene disk loading, handled by the game itself, everything else has to be reimplemented by the loaded code from disk.