The idea of using video games as a way to achieve some form of Arbitrary Code Execution (ACE) on classic hardware has come a long way since seven years ago, when TASbot publicly reprogrammed a Super NES on the fly via Super Mario World. There are now dozens of examples of similar glitches that use nothing but controller inputs to insert new programming instructions into classic games, including many that can be performed by humans (and not just button-mashing robots).
Even given all that history, though, we’re still a bit wowed by the speedrunning community that found a way to insert new code into Paper Mario for the N64, leading to a new record-setting speedrun of the game. Their new method requires some extremely careful character positioning, the exploitation of “junk” memory in the N64’s RAM expansion pack and, amazingly, playing a couple of games of The Legend of Zelda: Ocarina of Time.
Enter the effects matrix
The story of how this incredible method was discovered goes back two months, when a Paper Mario speedrunner who goes by Morpheus stumbled on a mysterious game crash in the middle of a livestreamed run. Players eventually discovered that Morpheus had accidentally triggered a situation where the game was storing too much data in the “effects matrix,” a data structure the game uses to store details of visual effects like smoke from Mario’s hammer blows.