There are accompanying materials that were used in the development process. The HW folder contains more or less coherent GAMECUBE documentation. In the RE folder is located Reverse Engineering of various software for GAMECUBE, as well as DSP UCodes and IPL BIOS reversing.
Old descriptions contain a lot of "Runglish", newer ones I compose using machine translation (Google Translate), so reading them is not so painful.
All documents are quietly redone as Markdown.
I also try to remove the silly style of presentation everywhere. We got older :p
Graphic schemes are created in the yEd (https://www.yworks.com/products/yed).