I recently purchased a SD2SNES which includes many enhancement chips. One such chip, MSU1 can actually play video and CD quality audio. I'm wondering, does anyone here know if there are any such enhancement chips for the NES? And if there isn't can't someone make some?
Advanced mappers, such as MMC5, are "enhancement chips" in a sense.
Early in its life, the NES received very simple enhancement chips, which did nothing more than allow the NES to access more than 32KB of PRG-ROM and 8KB of CHR-ROM, which are the system's limits. This primary function of mapping more memory to the limited addressing space granted these chips the name "mappers".
These enhancement chips got progressively more complex, implementing features like scanline counters, fine CHR animations, extra audio channels, access to more background and sprite tiles at once, finer background palette distribution, and even a multiplier to compensate the lack of this operation in the 6502.
Technically, a NES enhancement chip doing Super-FX or Cx4-style graphics extensions is perfectly possible on the NES. Unfortunately, the complexity of doing so implies that nobody really did that.
The closest that comes to mind is the MMC5's mode that can do either vertical split scrolling or to reduce attribute table granularity to 8x8 instead of 16x16.
Note that technically, anything that allows switchable CHR-ROM banks is a "graphical enhancement chip".
Bregalad wrote:
Technically, a NES enhancement chip doing Super-FX or Cx4-style graphics extensions is perfectly possible on the NES. Unfortunately, the complexity of doing so implies that nobody really did that.
Wide Boy and RetroVision include the entire Game Boy chipset, feeding a block of VRAM, on a cartridge that plugs into the Famicom or NES. But that's the only CPU-on-a-cart I can think of for the NES (other than the MCU in the CIC, but that's a completely separate bus).