Every original GameCube disc is exactly 1.35 GB, regardless of how much actual data is on it. This is because the console used a proprietary mini-DVD format that filled unused space with "garbage data" to ensure consistent read speeds.
Scrubbing: Tools like the GameCube ISO Tool or Wiimms ISO Tools (WIT) "scrub" the garbage data, leaving only the essential game files. gamecube games highly compressed hot
Why go highly compressed?
Conclusion
You don’t need to download sketchy pre-compressed ROMs from ad-filled forums. Do it yourself. Every original GameCube disc is exactly 1
Standard GameCube ISO files are always 1.35GB because the console’s hardware expected a full disc's worth of data. To fill this space, developers added "garbage" or "padding" data. Modern compression techniques can "scrub" or "trim" this data, dramatically reducing the file size without affecting gameplay. Dolphin Emulator (Desktop version, v5
GCZ Format: An older, standard compression format for Dolphin. While still functional, it is largely being replaced by RVZ because RVZ is more efficient and preserves metadata better.