There are some videos on youtube about programming and reverse engineering the Nintendo 64. Official development programs and cartridges, serial Joystick port hacking and assembler programming.
Nintendo N64 Source code Programming - A Basic Introduction
https://www.youtube.com/watch?v=d5YO2XMBvvk&t=651s
Nintendo N64 DEV: 64Drive Flashcart - Preview Sounds, Textures, and 3D Model "NIF" files over USB!
https://www.youtube.com/watch?v=yUX1Vga6amg&t=174s
RARE Nintendo N64 "IS-VIEWER 64" Development Cartridge - NOW WORKING!!
https://www.youtube.com/watch?v=Wx2YbPCwBCQ
N64 Hardware Architecture overview
https://www.youtube.com/watch?v=U2uuH_ICRks&t=1s
