system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why did Super Nintendo or Nintendo 64 games have almost no loading times?
gpt
An N64 cartridge has direct memory access, thus the processor sees the cartridge as memory that it can directly access, just like its predecessors (Super NES/Famicom and original NES/Famicom.)  

Unlike say the Switch, like its predecessors (Nintendo DS/3DS) sees that cart like a computer sees a harddrive: it loads files in RAM as they're needed, and unloads them when they're not. That takes time, hence the loading screens.