Covers the basics of Gamecube disc copy protection and how to use the SD Media Launcher to boot backup games:
Links:
https://debugmo.de/2008/11/anatomy-of-an-optical-medium-authentication/
http://www.nesworld.com/gcn-advancegameport.php
https://www.gc-forever.com/wiki/index.php?title=Main_Page
https://www.gc-forever.com/forums/viewtopic.php?f=3&t=3618