The "Super FX" chip is a RISC co-processor to the Graphics Support Unit used in some Super Nintendo cartridges, designed to aid in rendering 3D environments as the Super Nintendo's processor alone cannot. The chip was designed by Argonaut Software whom, alongside Nintendo, developed the original Star Fox to show off the chip's 3D graphics capability. Super FX is also used in 2D games.
Because of the longer development time required in order to utilise the chip, there are only 8 released games that use it. These games also have higher retail prices because the chip adds to manufacturing costs.
Due to licensing issues with the now-defunct Argonaut Games, it is unlikely any game that used the Super FX chip will make its way to Nintendo's Virtual Console platform.
While in development, the Super FX chip was codenamed "Super MARIO FX", with MARIO being an acronym for Mathematical, Argonaut, Rotation, Input/Output.
The Super FX chip is notable for being the first 3D accelerator used in a consumer-grade product, and also for becoming the best-selling RISC processor of that time.
There are two revisions of the Super FX chip. The original is a 21.4 MHz co-processor, but its internal clock divider halves this to 10.7Mhz. Star Fox uses this, as does Dirt Racer, Dirt Trax FX, Stunt Race FX, and Vortex. The chip can be identified by the phrase "MARIO CHIP 1" printed on the chip.
The second revision, known as either Super FX 2 or Super FX-GSU, is a 21MHz chip, and is combined with the Graphics Support Unit (hence the "GSU" in the name). This revision is identified by having "FX GSU-2-SP1" printed on it. Both revisions are compatible with each other in terms of code, however the Super FX 2 can actually reach 21MHz and use more RAM. Only 3 games were released with this chip: DOOM, Super Mario World 2: Yoshi's Island, and Winter Gold. The cancelled SNES version of Star Fox 2 was supposed to use this revision.
Any game that features the Super FX chip have more contact pins on the cartridge, meaning they can't be used in pre-Super FX cart adapters, such as the Game Genie cheat device.
Some uses have had success overclocking the Super FX chip, which makes the game itself play faster, giving the illusion of higher framerates. It is never recommended to overclock the chip on an official cartridge. Most SNES emulators that support emulating the Super FX chip can also emulate it at higher clock speeds.