Super FX is a Super Nintendo enhancement chip, mainly used to enhance graphical effects. Another name for the Super FX chip is the GSU (Graphical Support Unit). Super Mario World 2: Yoshi's Island and Star Fox are two notable games that used this enhancement chip.
It can be clocked to run either at 10.74 MHz (approximately 5 times faster than SNES), or at 21.48 MHz (approximately 10 times faster than SNES). It runs parallel to SNES' CPU. The Super FX chip also has 16 general-purpose registers, as opposed to the SNES CPU. When one is using Super FX, the maximum ROM size should never exceed 2MB. This makes it possible to use Super FX in Super Mario World too. The Super FX chip has been documented thoroughly in the SNES Developer Manual, book 2.
The Super FX chip can mainly be used for advanced graphical effects like dynamically updating graphics, generating tables, graphic decompression, and so on. Additionally, the Super FX is a programmable chip. You don't give it inputs and it gives you outputs (like the DSP-1) - you code the chip's functions yourself, and use the chip whenever you want to.
People think that this chip can scale and rotate sprites. This is NOT true. This chip only rotates and scales the sprite's GRAPHICS.
- Super FX has a different instruction set than the 65c816 CPU, and isn't capable of indexing and using the stack. You will have to code accordingly.
- Even though Super FX runs parallel to the SNES CPU, they both can't access the same area simultaneously. An example of this situation is: If you run the Super FX and access the ROM area for data, while you (the SNES) wait in a loop in the ROM area for Super FX to finish, the SNES CPU will crash, because it can't access the ROM area anymore - the SNES will read bogus opcodes. This can be solved by putting the SNES wait loop in the WRAM.
- A ROM using the Super FX chip is limited to 2 MB, due to the way the memory is mapped when the Super FX is present.