A lot of the knowledge is from patents and dev kit leaks. Also, it was built by Silicon Graphics and uses similar tech to their indigo workstations so some knowledge from those apply.
Just commenting to clarify that "hang Pence" trending was associated with folks sharing and retweeting videos of people chanting hang pence at the capitol. It was NOT an incitement to violence and to hang Pence. If anything, it was actually a condemnation of those calling to hang Pence.
N64 is well understood, and there are low level emulators now available that emulate the RSP and RDP on modern GPUs implemented with compute shaders. https://www.libretro.com/index.php/category/parallel-n64/