I think that he was able to gain access to hex-level memory and instructions through a GameShark (http://en.wikipedia.org/wiki/GameShark http://en.wikipedia.org

I think that he was able to gain access to hex-level memory and instructions through a GameShark (http://en.wikipedia.org/wiki/GameShark http://en.wikipedia.org/wiki/GameShark) playing on the N64, though he doesn't mention this directly.