Yamaha YM2612

Last updated
Yamaha YM2612 Yamaha YM2612 chip.jpg
Yamaha YM2612

The YM2612, a.k.a. OPN2, is a sound chip developed by Yamaha. It is a member of Yamaha's OPN family of FM synthesis chips, and is derived from the YM2203. [1]

Contents

The YM2612 is a six-channel FM synthesizer used in several game and computer systems, most notably in Sega's Mega Drive/Genesis video game console [2] as well as Fujitsu's FM Towns computer series. [3] It was also available in CMOS form as the YM3438, a.k.a. OPN2C. [1]

As with the YM3438, it was used by Sega in various arcade game systems, including the Mega-Play, Sega System C and Sega System 32; the YM3438 core was also integrated into an ASIC in later revisions of the Mega Drive/Genesis.

Features

The YM2612 has the following features: [1]

Technical details

The YM2612's FM synthesis block is an extended version of the FM block featured in the YM2203, adding three additional FM channels and integrating a stereo output DAC. [1] The YM2612 removes the SSG component (although retaining its envelope generators) and GPIO ports found in the YM2203 and YM2608, [1] which were elements of the integrated YM2149F core on the other OPN chips. While the YM2612 was mainly based on the YM2203, it was often referred to as being based on the YM2608 due to a number of similarities between the two sound chips, only lacking the latter's ADPCM channels among other aforementioned changes.

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. [1] 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. [2]

Low volume distortion of the built-in DAC

An example of the low volume distortion created by the peculiar qualities of the YM2612's built-in DAC. This sample is from the Mega Drive game Beyond Oasis .
In some cases, this low volume distortion can affect the loudness, and to some degree the timbres, of certain sounds. This sample is from the Mega Drive game Streets of Rage 2 .

Unlike most Yamaha FM chips which require an external floating-point DAC, the YM2612 features a built-in 9-bit DAC, which uses time-division multiplexing to play one sample of each channel in sequence, similar to the YM2413.

Due to an error with the amplitude voltage in the original chip design, a peculiar form of crossover distortion known as low volume distortion (and historically known as the "ladder effect" or "TDM distortion") is introduced in the output. Any output that is sufficiently low in volume undergoes an exaggerated quantization, including any usage of fades in video game music.

Some early games in the Mega Drive/Genesis' lifespan such as After Burner II had their music written around this distortion; consequently, the music would sound too quiet on later Mega Drive/Genesis consoles that used the integrated YM3438 chip on the ASIC. Also, because of the reduced dynamic range of the built-in DAC, additional distortion may be generated when playing sounds with a very high volume. [1]

In recent years, improvements in emulation accuracy of the sound chips resulted in the low volume distortion bug in the YM2612 being successfully emulated in software, and many recent Mega Drive/Genesis emulators since have offered this feature as an option to replicate the sound outputs of the original and revised models of the Mega Drive/Genesis. Other variants of the YM2612 that have also reduced the low volume distortion bug such as the YM3438 have also been emulated and implemented in many Mega Drive/Genesis emulators as well.

Variants

Yamaha YM3438

The YM3438, [1] a.k.a. OPN2C, is a modified CMOS version of the YM2612, commonly used in Sega's arcade system boards. This version has an improved built-in DAC with a higher signal-to-noise ratio than the YM2612 as well as a significantly reduced low volume distortion. It is not a direct, drop-in replacement for the YM2612 however, as the sound outputs have higher impedance.

Yamaha YMF276

The YMF276, [5] a.k.a. OPN2L, is a low-powered version of the YM3438, used in later models of the Fujitsu FM Towns series (particularly the FM Towns II models). It came in a smaller 24-pin SOP package. Unlike the YM2612 and YM3438, the YMF276 requires an external DAC chip, similar to most other Yamaha FM chips. This is usually a YM3433B external DAC chip (as used in the FM Towns II models) or other equivalent DAC chips. As such, it does not produce significant low volume distortion as with the YM2612/YM3438 chips due to its usage of an external DAC chip.

Sega Mega Drive/Genesis ASICs made by Yamaha (FC1004, FF1004, FJ3002 and FQ8007)

The YM3438 core was integrated in custom ASICs [6] used in the final revision of the Model 1 version and most revisions of the Model 2 version of the Sega Mega Drive/Genesis, as well as the Genesis 3 released by Majesco. The YM3438 core in these revisions further reduced the presence of the low volume distortion bug more so than with standalone YM3438 chips.

Game audio

Used in conjunction with the Texas Instruments SN76489 PSG as the main sound generators of the Sega Mega Drive/Genesis console, the YM2612 was prominently utilized by numerous prolific video game music composers, most notably Yuzo Koshiro. [4] [7]

See also

Related Research Articles

<span class="mw-page-title-main">Frequency modulation synthesis</span> Form of sound synthesis

Frequency modulation synthesis is a form of sound synthesis whereby the frequency of a waveform is changed by modulating its frequency with a modulator. The (instantaneous) frequency of an oscillator is altered in accordance with the amplitude of a modulating signal.

<span class="mw-page-title-main">Sound card</span> Expansion card that provides input and output of audio signals

A sound card is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term sound card is also applied to external audio interfaces used for professional audio applications.

<span class="mw-page-title-main">Digital-to-analog converter</span> 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.

<span class="mw-page-title-main">Sound Blaster</span> Family of sound cards by Creative Technology

Sound Blaster is a family of sound cards and audio peripherals designed by Creative Technology/Creative Labs of Singapore. The first Sound Blaster card was introduced in 1989.

<span class="mw-page-title-main">MOS Technology 6581</span> MOS Technology sound chip

The MOS Technology 6581/8580 SID is the built-in programmable sound generator chip of the Commodore CBM-II, Commodore 64, Commodore 128, and MAX Machine home computers.

<span class="mw-page-title-main">Yamaha DX7</span> Synthesizer

The Yamaha DX7 is a synthesizer manufactured by Yamaha Corporation from 1983 to 1989. It was the first successful digital synthesizer and is one of the best-selling synthesizers in history, selling more than 200,000 units.

The digital sound revolution refers to the widespread adoption of digital audio technology in the computer industry beginning in the 1980s.

<span class="mw-page-title-main">FM Towns</span> Japanese personal computer

The FM Towns is a Japanese personal computer built by Fujitsu from 1989 to 1997. It started as a proprietary PC variant intended for multimedia applications and PC games, but later became more compatible with IBM PC compatibles. In 1993, the FM Towns Marty was released; it is a game console compatible with existing FM Towns games.

<span class="mw-page-title-main">Yamaha YM2413</span> FM synthesis sound chip by Yamaha

The YM2413, a.k.a. OPLL, is an FM synthesis sound chip manufactured by Yamaha Corporation. It is related to Yamaha's OPL family of FM synthesis chips, and is a cost-reduced version of the YM3812 (OPL2).

<span class="mw-page-title-main">General Instrument AY-3-8910</span> Sound generation IC

The AY-3-8910 is a 3-voice programmable sound generator (PSG) designed by General Instrument (GI) 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 Bally 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, Tiki 100 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.

OPN may stand for:

<span class="mw-page-title-main">Yamaha YM2151</span> Sound chip developed by Yamaha

The Yamaha YM2151, also known as OPM is an eight-channel, four-operator sound chip. It was Yamaha's first single-chip FM synthesis implementation, being created originally for some of the Yamaha DX series of keyboards. Yamaha also used it in some of their budget-priced electric pianos, such as the YPR-7, -8, and -9.

A programmable sound generator (PSG) is a sound chip that generates audio wave signals built from one or more basic waveforms, and often some kind of noise. PSGs use a relatively simple method of creating sound compared to other methods such as frequency modulation synthesis or pulse-code modulation.

<span class="mw-page-title-main">Yamaha YM2203</span> Sound chip

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

<span class="mw-page-title-main">Yamaha YM2608</span> Sound chip

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

<span class="mw-page-title-main">Yamaha YM2610</span> Sound chip developed by Yamaha

The YM2610, a.k.a. OPNB, is a sound chip developed by Yamaha. It is a member of Yamaha's OPN family of FM synthesis chips, and related to the YM2608.

<span class="mw-page-title-main">Yamaha YMF292</span>

The YMF292, aka SCSP is a multi-function sound chip developed by Yamaha for the Sega Saturn, and was also used in Sega's arcade version of the Saturn, the ST-V, along with the Model 2 and Model 3.

The Yamaha YMZ280B, also known as PCMD8, is a sound chip produced by Yamaha Corporation. It is an eight-channel PCM/ADPCM sample-based synthesizer designed for use with video game machines, packaged in a 64-pin QFP.

The OPL series are a family of sound chips developed by Yamaha. The OPL series are low-cost sound chips providing FM synthesis for use in computing, music and video game applications.

References

  1. 1 2 3 4 5 6 7 8 YM3438 Application Manual (Japanese)
  2. 1 2 Sega Genesis Technical Manual - YM2612 section (updated with errors corrected)
  3. ↑ Purcaru, Bogdan Ion (13 March 2014). Games vs. Hardware. The History of PC video games: The 80's. p. 527. Retrieved 14 December 2017.
  4. 1 2 "Super Sonic: Creating the new sound of Sega's hedgehog hit". TheGuardian.com . 13 February 2020.
  5. ↑ Undocumented Sound Chips - Yamaha YMF276
  6. ↑ Sega Genesis 2 / Sega Mega Drive II Service Manual
  7. ↑ "Sega Mega Drive Mini review – a legacy truly honoured". TheGuardian.com . 19 September 2019.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.