Yamaha YM2612

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Yamaha YM2612 Yamaha YM2612 chip.jpg
Yamaha YM2612

The YM2612, a.k.a. OPN2, is a sound chip developed by Yamaha. It belongs to Yamaha's OPN family of FM synthesis chips used in several game and computer systems.

A sound chip is an integrated circuit designed to produce sound. It might do this through digital, analog or mixed-mode electronics. Sound chips normally contain things like oscillators, envelope controllers, samplers, filters and amplifiers. During the late 20th century, sound chips were widely used in arcade game system boards, video game consoles, home computers, and PC sound cards.

Yamaha Corporation Japanese multinational corporation and conglomerate

Yamaha Corporation is a Japanese multinational corporation and conglomerate with a very wide range of products and services, and power sports equipment. It is one of the constituents of Nikkei 225 and is the world's largest piano manufacturing company. The former motorcycle division became independent from the main company in 1955, forming Yamaha Motor Co., Ltd, although Yamaha Corporation is still the largest shareholder.

Frequency modulation synthesis

Frequency modulation synthesis is a form of sound synthesis where the frequency of a waveform, called the carrier, is changed by modulating its frequency with a modulator. The frequency of an oscillator is altered "in accordance with the amplitude of a modulating signal."



The Yamaha YM2612 is a six-channel FM synthesizer, based on the Yamaha YM2203C. It was most notably used in Sega's Mega Drive/Genesis video game console, [1] as well as Fujitsu's FM Towns computer series. [2] As with the YM3438, it was used by Sega in various arcade game systems, including the Mega-Play, System 18, and System 32.

Yamaha YM2203

The YM2203, a.k.a. OPN, is a three-channel sound chip developed by Yamaha. It was the progenitor of Yamaha's OPN family of FM synthesis chips used in many videogame and computer systems throughout the 1980s and early 1990s. The YM2203 itself was used in a variety of NEC computers, along with various arcade game machines.

Sega Japanese video game developer and publisher and subsidiary of Sega Sammy Holdings

Sega Games Co., Ltd. is a Japanese multinational video game developer and publisher headquartered in Tokyo. Its international branches, Sega of America and Sega Europe, are respectively headquartered in Irvine, California and London. Sega's arcade division, once part of Sega Corporation, has existed as Sega Interactive Co., Ltd. since 2015. Both companies are subsidiaries of Sega Holdings Co., Ltd., which is in turn a part of Sega Sammy Holdings.

Fujitsu Japanese multinational information technology equipment and services company

Fujitsu Ltd. is a Japanese multinational information technology equipment and services company headquartered in Tokyo, Japan. In 2018, it was the world's fourth-largest IT services provider measured by global IT services revenue. Fortune named Fujitsu as one of the world's most admired companies and a Global 500 company.


The YM2612 has the following features: [3]

Digital-to-analog converter device that converts a digital signal into an analog signal

In electronics, a digital-to-analog converter is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function.

Technical details

The YM2612 is an extended and integrated derivative of the FM synthesis block from the YM2203C, removing the SSG component (though retaining its envelope generator) and I/O port, and integrating a stereo output DAC. [3] It was also available in CMOS form, as the YM3438, a.k.a. OPN2C. [3]

General Instrument AY-3-8910 General Instrument AY-3-8910

The AY-3-8910 is a 3-voice programmable sound generator (PSG) designed by General Instrument in 1978, initially for use with their 16-bit CP1610 or one of the PIC1650 series of 8-bit microcomputers. The AY-3-8910 and its variants were used in many arcade games—Konami's Gyruss contains five—and pinball machines as well as being the sound chip in the Intellivision and Vectrex video game consoles, and the Amstrad CPC, Oric-1, Colour Genie, Elektor TV Games Computer, MSX, and later ZX Spectrum home computers. It was also used in the Mockingboard and Cricket sound cards for the Apple II and the Speech/Sound Cartridge for the TRS-80 Color Computer.

CMOS Technology for constructing integrated circuits

Complementary metal–oxide–semiconductor (CMOS) is a type of MOSFET semiconductor device fabrication process. CMOS technology is used for constructing integrated circuits (ICs), including microprocessors, microcontrollers, memory chips, and other digital logic circuits. CMOS technology is also used for several analog circuits such as image sensors, data converters, and highly integrated transceivers for many types of communication. CMOS was invented by Chih-Tang Sah and Frank Wanlass at Fairchild Semiconductor in 1963, and was an adaptation of the PMOS and NMOS processes originally developed by MOSFET inventors Mohamed Atalla and Dawon Kahng in 1960. CMOS became the dominant MOSFET fabrication process for VLSI devices since it overtook NMOS in the 1980s.

Whereas the high-end OPN chips such as the YM2608 have dedicated ADPCM channels for playing sampled audio, the YM2612 does not. However, its sixth channel can act as a basic PCM channel by means of the 'DAC Enable' register, disabling FM output for that channel but allowing it to play 8-bit pulse-code modulation sound samples. [3] Unlike the other OPNs with ADPCM, the YM2612 does not provide any timing or buffering of samples, so all frequency control and buffering must be done in software by the host processor. [1]

Yamaha YM2608

YM2608, a.k.a. OPNA, is a sixteen-channel sound chip developed by Yamaha. It's a member of Yamaha's OPN family of FM synthesis chips, and the successor to the YM2203. It was notably used in NEC's PC-8801/PC-9801 series computers.

Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps.

Output DAC peculiarities

An example of the crossover distortion created by the peculiar qualities of the YM2612's built-in DAC.
In some cases, the crossover distortion can affect the loudness, and to some degree the timbres, of certain sounds.

Unlike most Yamaha FM chips which require an external floating-point DAC, the YM2612 features a built-in 9-bit DAC, which utilizes time-division multiplexing to play one sample of each channel in sequence, similar to the YM2413.[ citation needed ] This method introduces a peculiar form of crossover distortion in the output, which has become known as the "ladder effect" among fans.[ citation needed ]

Time-division multiplexing multiplexing technique for digital signals

Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern. It is used when the bit rate of the transmission medium exceeds that of the signal to be transmitted. This form of signal multiplexing was developed in telecommunications for telegraphy systems in the late 19th century, but found its most common application in digital telephony in the second half of the 20th century.

Crossover distortion

Crossover distortion is a type of distortion which is caused by switching between devices driving a load. It is most commonly seen in complementary, or "push-pull", Class-B amplifier stages, although it is occasionally seen in other types of circuits as well.

Additionally, because of the reduced dynamic range of the built-in DAC, additional distortion may be generated when playing sounds with a very high volume. [3]


Yamaha YM3438

The YM3438, [3] a.k.a. OPN2C, is a modified CMOS version of the YM2612. It is not a direct, drop-in replacement for the YM2612 however, as the sound outputs have higher impedance.

Yamaha YMF276

The YMF276, a.k.a. OPN2L, is a low-power version of the YM3438. Unlike YM2612 and YM3438, the YMF276 requires external DAC.

Yamaha Fx1004 and FJ3002

The YM3438 core was integrated in custom ASICs [4] used in most revisions of the Model 2 version of the Sega Mega Drive/Genesis.

Game audio

As the main sound generator of the Sega Mega Drive/Genesis console, the YM2612 was prominently utilized by numerous prolific video game music composers, such as Yuzo Koshiro.

See also

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  1. 1 2 Sega Genesis Technical Manual - YM2612 section (updated with errors corrected)
  2. Games vs. Hardware. The History of PC video games: The 80's. p. 527. Retrieved 14 December 2017.
  3. 1 2 3 4 5 6 YM3438 Application Manual (Japanese)
  4. https://console5.com/techwiki/images/5/57/Sega_Service_Manual_-_Genesis_II_-_Mega_Drive_II_%28PAL-B-I-G%2C_RGB%29%2C_No_001%2C_June%2C_1993.pdf