Mapper

A mapper is a piece of hardware soldered to a cartridge's printed circuit board that performs address decoding, bank switching, and possibly other tasks. Some mappers can generate interrupts for timing; some Famicom games' mappers even have extra audio channels.

NES cartridges can include extra hardware which allows the use of large program and graphics ROMs and extra features. This extra hardware is usually referred to as a "mapper", as it is used primarily to map the relatively small CPU and PPU address spaces to a portion of the larger address space of the ROM(s) on the cartridge.

Mappers vary in how they translate addresses. The various CPU memory mapping schemes expand the maximum program size above the standard 32 KiB to larger powers of 2, while PPU memory mapping schemes can add new graphic features.

Most mappers fall into one of two categories: discrete logic, and ASIC based. Some discrete logic mappers are susceptible to bus conflicts. Nintendo uses the term Memory Management Controller (or MMC for short) for its ASIC mappers ("Why Game Paks Never Forget" article in Nintendo Power).

Discrete logic mappers are often referred to by the name of a board that they are commonly used in (e.g. "UNROM"). ASIC mappers are named after the ASIC (e.g. "MMC1" or "FME-7"), except in boards that use an ASIC in an unusual way (such as "TQROM", "TLSROM", or "NES-EVENT"). The emulation community generally refers to mappers by a numbering scheme that originated with the iNES emulator (e.g. "mapper 002").

iNES 1.0 mapper grid

000	001	002	003	004	005	006	007	008	009	010	011	012	013	014	015
016	017	018	019	020	021	022	023	024	025	026	027	028	029	030	031
032	033	034	035	036	037	038	039	040	041	042	043	044	045	046	047
048	049	050	051	052	053	054	055	056	057	058	059	060	061	062	063
064	065	066	067	068	069	070	071	072	073	074	075	076	077	078	079
080	081	082	083	084	085	086	087	088	089	090	091	092	093	094	095
096	097	098	099	100	101	102	103	104	105	106	107	108	109	110	111
112	113	114	115	116	117	118	119	120	121	122	123	124	125	126	127
128	129	130	131	132	133	134	135	136	137	138	139	140	141	142	143
144	145	146	147	148	149	150	151	152	153	154	155	156	157	158	159
160	161	162	163	164	165	166	167	168	169	170	171	172	173	174	175
176	177	178	179	180	181	182	183	184	185	186	187	188	189	190	191
192	193	194	195	196	197	198	199	200	201	202	203	204	205	206	207
208	209	210	211	212	213	214	215	216	217	218	219	220	221	222	223
224	225	226	227	228	229	230	231	232	233	234	235	236	237	238	239
240	241	242	243	244	245	246	247	248	249	250	251	252	253	254	255

See also

• Nintendo: MMC1, MMC2, MMC3, MMC4, MMC5 with audio, MMC6
• Konami: VRC1, VRC2, VRC3, VRC4, VRC6 with audio, VRC7 with audio, VRC irqs
• Others: Color Dreams, Namco 106 with audio, NINA-001, NINA-03/06, SUBOR, Sunsoft FME-7
• List of discrete logic mappers
• List of iNES mapper numbers
• Comparison of Nintendo mappers
• List of mapper names and corresponding iNES mapper numbers
• Hardware pinout, including mapper pinouts

External links

• Disch's detailed list of over 50 mappers at romhacking.net