Hacking SNES Games with Coprocessors to Improve Their Speed

The Super Nintendo has earned its popularity, but over the years we have learned many details about that console, including its limitations. To be honest, the Ricoh 5A22 processor wasn't very powerful for the time, which forced the addition of extra hardware in cartridges, though some games suffered serious speed issues. One of the most affected was Gradius III; however, a Brazilian hacker named Vitor Vilela developed a patch that allows that title to use an SA-1 coprocessor, eliminating its slowdowns and maintaining a stable framerate.

When playing on computers, we can always make adjustments to improve the performance of a specific title. The most common involve visual quality and resolution, but there are also tricks in graphics engines, controller mods, and the occasional overclocking session that pushes our components a bit further.

In the case of modern video game consoles, developers can release patches to optimize their games, but when it comes to older platforms... what you see is what you get. A striking example is Gradius III for the Super Nintendo. The port looks great, and visually it has almost nothing to envy from the arcade version. Unfortunately, that means it eats the Ricoh 5A22 processor like candy, and in several instances, the experience falls apart. The second level is one of the most affected.

Anyone at this point would recommend playing Gradius III on an emulator, but not the Brazilian hacker Vitor Vilela. What he did was invest three months in research, analysis, and code editing, memory mapping, and disassembly to make Gradius III compatible with the SA-1 coprocessor.

SA-1: A Coprocessor in the Super Nintendo

This chip was used in games like Super Mario RPG and Kirby Super Star, and it is essentially a supercharged 5A22, with higher frequency (10.74 MHz vs. 3.58 MHz), accelerated math functions, optimized graphics manipulation, and parallel processing.

The best part is that anyone interested can take this "modified SA-1 edition" of Gradius III, dump its contents onto a cart at the level of the SD2SNES (which costs $150), and play on a real Super Nintendo without doing anything extra to the console. A potentially cheaper alternative for those who want to reproduce the benefits of this hack on the metal is to look for a compatible donor cartridge and create it yourself, following the steps of YouTuber Voultar:

What's next on the list? Vitor plans to add other games with performance problems to his new SA-1 era. Much of his activity is available through Patreon, but you have to think very carefully before modifying a game. Why? Because the change in speed can increase the difficulty level... a lot.

Source: Hackaday, via Ars Technica