Introduction
The Super FX chip, also known as the Graphics Support Unit (GSU), is a custom 16‑bit RISC coprocessor developed by Argonaut Games in partnership with Nintendo. It was built directly into certain Super Nintendo Entertainment System cartridges rather than the console itself, giving the SNES a way to handle graphics the base hardware could not manage on its own. The original version, often called the MARIO chip, short for Mathematical, Argonaut, Rotation and Input/Output, first appeared in Star Fox in 1993. It runs at an external clock speed of 21.4 MHz, though early versions divide this internally to around 10.7 MHz.Inside a Star Fox cartridge: the MARIO chip, Nintendo’s first step toward real‑time 3D graphics on the SNES.
The Super FX 2 Revision
A later revision, known as Super FX 2 or GSU‑2, removes this limitation, allowing it to run at the full 21 MHz. It also supports larger ROM sizes, up to 2 MB, and more RAM, typically between 64 KB and 128 KB. Both versions include 512 bytes of instruction cache, allowing most instructions to execute in a single cycle. Overall, the chip can perform calculations roughly four times faster than the SNES’s main CPU.The GSU‑2, a refined version of the original Super FX, manufactured in 1993.
How the Chip Works
The Super FX acts as a dedicated graphics accelerator. It handles demanding tasks like 3D polygon rendering, vertex transformations using fixed‑point 16‑bit math, and matrix calculations for rotation, scaling, and projection. It can also manage basic texture mapping, sprite scaling and rotation, parallax scrolling, and direct pixel drawing into a frame buffer stored in cartridge RAM. Because it uses fixed‑point math instead of floating‑point, it is faster but less precise. Once rendering is finished, the SNES Picture Processing Unit displays the final image.Performance and Limitations
This setup allowed the SNES to display hundreds of flat‑shaded polygons per frame, usually at around 15 to 20 frames per second in well‑optimized games. It also enabled advanced 2D effects like rotating and stretching sprites. However, the chip shares memory with the main system and cannot access the same RAM at the same time as the SNES CPU, which made development more complicated.Games That Used the Super FX
Because of the higher manufacturing cost and the added complexity for developers, only a small number of games used the Super FX. Notable examples include Star Fox, which served as a showcase for its 3D capabilities; Stunt Race FX (known as Wild Trax in Japan), a polygon‑based racing game; Vortex, a 3D action title; Dirt Trax FX and Dirt Racer for off‑road racing; and the SNES version of Doom, which used the chip for its pseudo‑3D environments. Super Mario World 2: Yoshi’s Island took a different approach, using the Super FX 2 mainly for 2D effects like rotating platforms and dynamic backgrounds rather than heavy polygon use. Winter Gold was also released in some regions. Other projects, such as Star Fox 2, were completed but not released at the time, only appearing years later in official collections.Gameplay from Stunt Race FX, showing polygon cars on a dirt track
