Welcome the the Nintendo NES Mappers section of The Low Level. Here you will find documentation I have written on the NES mapper hardware.
Mappers are hardware in cartridges in addition to the ROM/RAMs which enhance the NES' capabilities. By default, the NES only supports games with a maximum of 32K of PRG and 8K of CHR ROM/RAM, 2K of WRAM and 2K of VRAM. However, the NES is a very extendable system, and through mapper hardware, bankswitching, graphical and audio enhancements, and other extensions can be performed. Mappers allow for a virtually unlimited amount of PRG and CHR memory space, increased background tiles, increased background tile attributes, battery backed save games, and so on.
Launched in North America in 1985, by 1986, most NES games already began using mapper hardware, as 32K of PRG ROM just couldn't achieve the gameplay experience developers required. Mappers vary from simple and straight forward such as the CNROM, to incredibly complex, such as the MMC5.
While building my NES development hardware, I began analyzing the mappers and how they worked. Also, with the help of the Devtendo unit I built, when I come across an obscure cartridge, I will occasionally reverse engineer it for fun. Below are some of the documents I have written detailing my findings.
News
[2004-12-22 17:43] Nintendo MMC5 Cartridge ROM Pinouts
Here's another MMC5 document... the ROM pinouts! I posted these back on the old NESDEV message boards a while back, but here they are, updated, and easily accessible!
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[2004-12-22 17:43] Nintendo MMC5 EXRAM Nametable Information
I've posted some updated versions of old documents/notes I wrote about the Nintendo MMC5 mapper. This document describes how to properly access/write to the nametable EXRAM in MMC5 games.
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[2004-09-08 17:43] NES-UNROM Mapper Information
Here's some new documentation I've written on Nintendo's NES-UNROM board. Includes pinouts for the ICs as they are used by the board (rather than just the datasheet pin names).
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[2004-08-15 17:43] FunStation Multicart Mapper Information
I recently picked up a FunStation One famiclone, which came with this multicart. It's a typical first-gen multicart, but with interesting graphic hacks and such. For the sake of science, I decided to reverse engineer it's mapper, dump it, document it, and write the emulator mapper support code. All so the world can see another game similar to what the've seen many times before, haha.
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