The Ricoh 2A03 or RP2A03 (NTSC version) / Ricoh 2A07 or RP2A07 (PAL version) is an 8-bit microprocessor manufactured by Ricoh for the Nintendo Entertainment System video game console. It was also used as a sound chip and secondary CPU by Nintendo's arcade games Punch-Out!! and Donkey Kong 3.
 | |
| General information | |
|---|---|
| Launched | 1982 |
| Discontinued | 2003 |
| Common manufacturer | |
| Performance | |
| Max. CPU clock rate | 1.79 MHz |
| Architecture and classification | |
| Technology node | 6 μm |
| Instruction set | MOS 6502 |
| Physical specifications | |
| Cores |
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| Socket |
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Technical details
The Ricoh 2A03[1] contained a second sourced MOS Technology 6502 core, modified to disable the 6502's binary-coded decimal mode (possibly to avoid a MOS Technology patent[2]). It also integrated a programmable sound generator (also known as APU, featuring twenty two memory-mapped I/O registers),[3] rudimentary DMA, and game controller polling.[4]
Sound Hardware
The Ricoh 2A03's sound hardware has 5 channels, separated into two APUs (Audio Processing Unit). The first APU contains two general purpose pulse channels with 4 duty cycles, and the second APU contains a Triangle wave generator, a LFSR-based Noise generator, and one Delta-Modulated PCM (DPCM) channel. While a majority of the NES library used only 4 channels, more games later into the NES's life span used the 5th DPCM channel, as memory mappers became more common and prices of ROM chips became cheaper. For example, Super Mario Bros. 3 uses it for simple drum sounds, while other games like Journey to Silius use it for sampled basslines. An interesting quirk of the DPCM channel is that the bit order is reversed compared to what is normally expected for input, as a result, many games often ignore this quirk, which results in distorted sounding samples.[5]
The sound output by the Ricoh 2A03 is present on two pins, which are then mixed using a non-linear mixing circuit. On Famicom and Dendy systems, this is then output to the cartridge slot, where an expansion sound chip may add its own mixed sound into the resulting output, which is then fed back into the console. International NES systems instead output the 2A03's sound directly to the TV, but expansion sound functionality can be restored by a simple pin mod on the expansion port, allowing the internal mixer to add the cartridge's expansion sound output from the expansion port.[6]
Regional variations
PAL versions of the NES (sold in Europe, Asia, and Australia) used the Ricoh 2A07 or RP2A07 processor, which was identical to the 2A03 except for a different clock divider and the 50 Hz vertical refresh rate used in the PAL television standard, with the exception of the 16 hard-coded sampling rates for the Delta modulation-encoded sample playback unit. The changes were made in order for sampled sounds to maintain the original pitch of the RP2A03 with the new clock divider. Most developers however, usually lacked the resources to properly convert their games to the 2A07, leading to most games often sounding out of tune or off-tempo.
See also
References
- ^ Sattler, Christian. "Nintendo RP2A03 and RP2A07 - an high quality picture of the die". visual6502.org. Retrieved 2020-08-12..
- ^ Patent US3991307
- ^ "Sound generators of the 1980s home computers". www.atkinsoft.com. Retrieved 2019-12-02.
- ^ Taylor, Brad (April 23, 2004). "2A03 technical reference". NesDev.com. Archived from the original on October 17, 2018. Retrieved June 6, 2008.
- ^ The Cutting Room Floor https://tcrf.net/Ufouria:_The_Saga#Sound_Design_Quirks. Retrieved 9 October 2021.
{{cite web}}: Missing or empty|title=(help) - ^ Burke, Kevin. "NES Expanded Audio: 100k Pot Mod". The Curriculum Crasher. Retrieved 9 October 2021.
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