MOS Technology 6581

Last updated
MOS Technology SIDs. The right chip is a 6581 from MOS Technology, known at the time as the Commodore Semiconductor Group (CSG.) The left chip is an 8580, also from MOS Technology. The numbers 0488 and 3290 are in WWYY form, i.e. the chips were produced week 4 1988 and week 32 1990. The last number is assumed to be a batch number. MOS Technologies 6581.jpg
MOS Technology SIDs. The right chip is a 6581 from MOS Technology, known at the time as the Commodore Semiconductor Group (CSG.) The left chip is an 8580, also from MOS Technology. The numbers 0488 and 3290 are in WWYY form, i.e. the chips were produced week 4 1988 and week 32 1990. The last number is assumed to be a batch number.

The MOS Technology 6581/8580 SID (Sound Interface Device) is the built-in programmable sound generator chip of Commodore's CBM-II, Commodore 64, [1] Commodore 128 and Commodore MAX Machine home computers. It was one of the first sound chips of its kind to be included in a home computer prior to the digital sound revolution.

Contents

Together with the VIC-II graphics chip, the SID was instrumental in making the C64 the best-selling home computer in history, [2] and is partly credited for initiating the demoscene.

Design process

The SID was devised by engineer Robert "Bob" Yannes, who later co-founded the Ensoniq digital synthesizer and sampler company. Yannes headed a team that included himself, two technicians and a CAD operator, who designed and completed the chip in five months in the latter half of 1981. Yannes was inspired by previous work in the synthesizer industry and was not impressed by the current state of computer sound chips. Instead, he wanted a high-quality instrument chip, which is the reason why the SID has features like the envelope generator, previously not found in home computer sound chips. [3] [4] :235

I thought the sound chips on the market, including those in the Atari computers, were primitive and obviously had been designed by people who knew nothing about music. [4] :235

Robert Yannes, On the Edge: The Spectacular Rise and Fall of Commodore

Emphasis during chip design was on high-precision frequency control, and the SID was originally designed to have 32 independent voices, sharing a common oscillator.[ clarification needed ] [4] :235 However, these features could not be finished in time, so instead the mask work for a certain working oscillator was simply replicated three times across the chip's surface, creating three voices each with its own oscillator. Another feature that was not incorporated in the final design was a frequency look-up table for the most common musical notes, a feature that was dropped because of space limitations. [4] :236 The support for an audio input pin was a feature Yannes added without asking, which in theory would have allowed the chip to be used as a simple effect processor. The masks were produced in 7-micrometer technology to gain a high yield; the state of the art at the time was 6-micrometer technologies. [4] :236

The chip, like the first product using it (the Commodore 64), was finished in time for the Consumer Electronics Show in the first weekend of January 1982. Even though Yannes was partly displeased with the result, his colleague Charles Winterble said: "This thing is already 10 times better than anything out there and 20 times better than it needs to be." [4] :237

The specifications for the chip were not used as a blueprint. Rather, they were written as the development work progressed, and not all planned features made it into the final product. Yannes claims he had a feature-list of which three quarters made it into the final design. The later revision (8580) was revised to more closely match the specifications. For example, the 8580 slightly improved upon the ability to perform a binary AND between two waveforms, which the SID can only do in a somewhat odd and unintuitive manner. Wave combinations on the 8580 are a bit “cleaner” than on the 6581. Another feature that differs between the two revisions is the filter, as the 6581 version is far away from the specification.[ citation needed ]

Manufacturing, remarking, and forgery

Since 6581 and 8580 SID ICs are no longer produced, they have become highly sought after. In late 2007, various defective chips started appearing on eBay as supposedly "new". [5] All of these remarked SIDs have a defective filter, but some also have defective channels/noise generators, and some are completely dead. The remarked chips are assumed to either be factory rejects from back when the chip was still produced, or possibly "reject pulls" from one of the chip pulling operations that were used to supply the chips used in the Elektron SIDStation and the HardSID cards. Fake SID chips have also been supplied to unwitting buyers from unscrupulous manufacturers in China; the supplied chips are laser-etched with completely bogus markings, and the chip inside the package is not a SID at all.[ citation needed ]

Features

Technical details

6581/6582/8580R5 Pin configuration MOS6581.svg
6581/6582/8580R5 Pin configuration

The SID is a mixed-signal integrated circuit, featuring both digital and analog circuitry. All control ports are digital, while the output ports are analog. The SID features three-voice synthesis, where each voice may use one of at least five different waveforms: pulse wave (with variable duty cycle), triangle wave, sawtooth wave, pseudorandom noise (called white noise in documentation), and certain complex/combined waveforms when multiple waveforms are selected simultaneously. A voice playing Triangle waveform may be ring-modulated with one of the other voices, where the triangle waveform's bits are inverted when the modulating voice's msb is set, producing a discontinuity and change of direction with the Triangle's ramp. Oscillators may also be hard-synced to each other, where the synced oscillator is reset whenever the syncing oscillator's msb raises.

Each voice may be routed into a common, digitally controlled analog 12 dB/octave multimode filter, which is constructed with aid of external capacitors to the chip. The filter has lowpass, bandpass and highpass outputs, which can be individually selected for final output amplification via master volume register. Using a combined state of lowpass and highpass results in a notch (or inverted bandpass) output. [7] The programmer may vary the filter's cut-off frequency and resonance. An external audio-in port enables external audio to be passed through the filter.

The ring modulation, filter, and programming techniques such as arpeggio (rapid cycling between 2 or more frequencies to make chord-like sounds) together produce the characteristic feel of SID music.

Due to imperfect manufacturing technologies of the time and poor separation between the analog and digital parts of the chip, the 6581's output (before the amplifier stage) was always slightly biased from the zero level. Each time the volume register was altered, an audible click was produced. By quickly adjusting the amplifier's gain through the main 4-bit volume register, this bias could be modulated as PCM, resulting in a "virtual" fourth channel allowing 4-bit digital sample playback. The glitch was known and used from an early point on, first by Electronic Speech Systems to produce sampled speech in games such as Impossible Mission (1983, Epyx) and Ghostbusters (1984, Activision). The first instance of samples being used in actual musical compositions was by Martin Galway in Arkanoid (1987, Imagine), although he had copied the idea from an earlier drum synthesizer package called Digidrums. The length of sampled sound playback was limited first by memory and later technique. Kung Fu Fighting (1986), a popular early sample, has a playback length measured in seconds. c64mp3 (2010) and Cubase64 (2010) demonstrate playback lengths measured in minutes. Also, it was hugely CPU intensive - one had to output the samples very fast (in comparison to the speed of the 6510 CPU).

The better manufacturing technology in the 8580 used in the later revisions of Commodore 64C and the Commodore 128DCR caused the bias to almost entirely disappear, causing the digitized sound samples to become very quiet. Fortunately, the volume level could be mostly restored with either a hardware modification (biasing the audio-in pin), or more commonly a software trick involving using the Pulse waveform to intentionally recreate the required bias. The software trick generally renders one voice temporarily unusable, although clever musical compositions can make this problem less noticeable. An excellent example of this quality improvement noticeably reducing a sampled channel can be found in the introduction to Electronic Arts' game Skate or Die (1987). The guitar riff played is all but missing when played on the Commodore 64c or the Commodore 128.

At the X'2008 demo party, a completely new method of playing digitized samples was unveiled. The method allows for an unprecedented four (software-mixed) channels of 8-bit samples with optional filtering on top of all samples, as well as two ordinary SID sound channels. [8] [9] The method works by resetting the oscillator using the waveform generator test bit, quickly ramping up the new waveform with the Triangle waveform selected, and then disabling all waveforms, resulting in the DAC continuing to output the last value---which is the desired sample. This continues for as long as two scanlines, which is ample time for glitch-free, arbitrary sample output. It is however more CPU-intensive than the 4-bit volume register DAC trick described above. Because the filtering in a SID chip is applied after the waveform generators, samples produced this way can be filtered normally.

The original manual for the SID mentions that if several waveforms are enabled at the same time, the result will be a binary AND between them. What happens in reality is that the input to the waveform DAC pins receive several waveforms at once. For instance, the Triangle waveform is made with a separate XOR circuit and a shift-to-left circuit. The top bit drives whether the XOR circuit inverts the accumulator value seen by the DAC. Thus, enabling triangle and sawtooth simultaneously causes adjacent accumulator bits in the DAC input to mix. (The XOR circuit does not come to play because it is always disabled whenever the sawtooth waveform is selected.) The pulse waveform is built by joining all the DAC bits together via a long strip of polysilicon, connected to the pulse control logic that digitally compares current accumulator value to the pulse width value. Thus, selecting the pulse waveform together with any other waveform causes every bit on the DAC to partially mix, and the loudness of the waveform is affected by the state of the pulse.

The noise generator is implemented as a 23-bit-length Fibonacci LFSR (Feedback polynomial: x^22+x^17+1). [10] [11] When using noise waveform simultaneously with any other waveform, the pull-down via waveform selector tends to quickly reduce the XOR shift register to 0 for all bits that are connected to the output DAC. As the zeroes shift in the register when the noise is clocked, and no 1-bits are produced to replace them, a situation can arise where the XOR shift register becomes fully zeroed. Luckily, the situation can be remedied by using the waveform control test bit, which in that condition injects one 1-bit into the XOR shift register. Some musicians are also known to use noise's combined waveforms and test bit to construct unusual sounds.

The 6581 and 8580 differ from each other in several ways. The original 6581 was manufactured using the older NMOS process, which used 12V DC to operate. The 6581 is very sensitive to static discharge and if they weren't handled properly the filters would stop working, explaining the reason of the great quantity of dead 6581s in the market. The 8580 was made using the HMOS-II process, which requires less power (9V DC), and therefore makes the IC run cooler. The 8580 is thus far more durable than the 6581. Also, due to stabler waveform generators, the bit-mixing effects are less noticeable and thus the combined waveforms come close to matching the original SID specification (which stated that they will be combined as a binary AND). The filter is also very different between the two models, with the 6581 cutoff range being a relatively straight line on a log scale, while the cutoff range on the 8580 is a straight line on a linear scale, and is close to the designers' actual specifications. Additionally, a better separation between the analog and the digital circuits made the 8580's output less noisy and distorted. The noise in 6xxx-series systems can be reduced by disconnecting the audio-in pin.

The consumer version of the 8580 was rebadged the 6582, even though the die on the chip is identical to a stock 8580 chip, including the '8580R5' mark. Dr. Evil Laboratories used it in their SID Symphony expansion cartridge (sold to Creative Micro Designs in 1991), and it was used in a few other places as well, including one PC sound-card.

Despite its documented shortcomings, many SID musicians prefer the flawed 6581 chip over the corrected 8580 chip. The main reason for this is that the filter produces strong distortion that is sometimes used to produce simulation of instruments such as a distorted electric guitar. Also, the highpass component of the filter was mixed in 3 dB attenuated compared to the other outputs, making the sound more bassy. In addition to nonlinearities in filter, the D/A circuitry used in the waveform generators produces yet more additional distortion that made its sound richer in character.

Revisions

6581R1 produced in 1982 SID 6581R1.jpg
6581R1 produced in 1982
6581 produced in 1982 6581 in ceramic DIP.jpg
6581 produced in 1982
6581R4 CDIP produced in 1986 6581R4 in cermaic DIP manufactured in week 11 of 1986.jpg
6581R4 CDIP produced in 1986
6582 produced in 1986 MOS SID 6582.jpg
6582 produced in 1986
6582A produced in 1989 6582A.jpg
6582A produced in 1989
6582A produced in 1992 CSG 6582A.jpg
6582A produced in 1992
8580R5 produced 1986 in the U.S. 8580R5 USA.jpg
8580R5 produced 1986 in the U.S.

No instances reading "6581 R1" ever reached the market. In fact, Yannes has stated that "[the] SID chip came out pretty well the first time, it made sound. Everything we needed for the show was working after the second pass." High-resolution photos of Charles Winterble's prototype C64 show the markings "MOS 6581 2082", the last number being a date code indicating that his prototype SID chip was produced during the 20th week of 1982, which would be within 6 days of May 17, 1982.

These are the known revisions of the various SID chips: (date codes are in WWYY w=week y=year format)

Some of these chips are marked "CSG" ("Commodore Semiconductor Group") and the Commodore Logo, while others are marked with "MOS". This includes chips produced during the same week (and thus, receiving the same date code), indicating that at least two different factory lines were in operation during that week. The markings of chips varied by factory and even by line within a factory throughout most of the manufacturing run of the chip.

Game audio

The majority of games produced for the Commodore 64 made use of the SID chip, with sounds ranging from simple clicks and beeps to complex musical extravaganzas or even entire digital audio tracks. Due to the technical mastery required to implement music on the chip, and its versatile features compared to other sound chips of the era, composers for the Commodore 64 have described the SID as a musical instrument in its own right. [12] Most software did not use the full capabilities of SID, however, because the incorrect published specifications caused programmers to only use well-documented functionality. Some early software, by contrast, relied on the specifications, resulting in inaudible sound effects. [3]

Well known composers of game music for this chip are Martin Galway, known for many titles, including Wizball , and Rob Hubbard, known for titles such as ACE 2 , Commando , Delta , International Karate , IK+ , and Monty on the Run . Other noteworthies include Jeroen Tel (Cybernoid, Turbo Outrun , Robocop 3 and Myth), Ben Daglish ( The Last Ninja , Jack the Nipper , Firelord, Gauntlet ), David Dunn ( Finders Keepers and Flight Path 737), David Whittaker ( Speedball , BMX Simulator, Glider Rider ) and Chris Hülsbeck ( R-Type , Turrican and The Great Giana Sisters ).

Emulation

The fact that many enthusiasts prefer the real chip sound over software emulators has led to several recording projects aiming to preserve the authentic sound of the SID chip for modern hardware.

The sid.oth4 project [13] has over 380 songs of high quality MP3 available recorded on hardsid hardware and the SOASC= project [14] has the entire High Voltage SID Collection (HVSC) released with 49 (over 35,000 songs) recorded from real Commodore 64s in a high quality MP3 file. Both projects emphasize the importance of preserving the authentic sound of the SID chip. In 2016, the Unepic Stoned High SID Collection (USHSC) [15] was launched. It is a YouTube channel with over 50,000 SID tunes uploaded as single videos. The USHSC is based on both the SOASC= and HVSC, but also uploads recordings of recent SID music released at the Commodore Scene Database (CSDb) site. The channel features playlists containing roughly 5000 tunes each.

Software emulation

A SID file contains the 6510 program code and associated data needed to replay the music on the SID. The SID files have the MIME media type audio/prs.sid.

The actual file format of a SID file has had several versions. The older standard is PSID (current version V4). The newer standard, RSID, is intended for music that requires a more complete emulation of the Commodore 64 hardware. [16]

The SID file format is not a native format used on the Commodore 64 or 128, [16] but a format specifically created for emulator-assisted music players such as PlaySID , Sidplay and JSidplay2. [17] However, there are loaders like RealSIDPlay and converters such as PSID64 [18] that make it possible to play a substantial portion of SID files on original Commodore computers.

Hardware reimplementations

Hardware implementations using the SID chip

SID hardware clones

See also

Related Research Articles

Commodore 64 8-bit home computer introduced in 1982

The Commodore 64, also known as the C64 or the CBM 64, is an 8-bit home computer introduced in January 1982 by Commodore International. It has been listed in the Guinness World Records as the highest-selling single computer model of all time, with independent estimates placing the number sold between 10 and 17 million units. Volume production started in early 1982, marketing in August for US$595. Preceded by the Commodore VIC-20 and Commodore PET, the C64 took its name from its 64 kilobytes(65,536 bytes) of RAM. With support for multicolor sprites and a custom chip for waveform generation, the C64 could create superior visuals and audio compared to systems without such custom hardware.

A signal generator is an electronic device that generates repeating or non-repeating electronic signals in either the analog or the digital domain. These generated signals are used as a stimulus for electronic measurements, typically used in designing, testing, troubleshooting, and repairing electronic or electroacoustic devices, though it often has artistic uses as well.

Chiptune music created through 8-bit sound chips

Chiptune, also known as chip music or 8-bit music, is a style of synthesized electronic music made using the programmable sound generator (PSG) sound chips in vintage arcade machines, computers and video game consoles. The term is commonly used to refer to tracker format music which intentionally sounds similar to older PSG-created music, as well as music that combines PSG sounds with modern musical styles. It has been described as "an interpretation of many genres" since any existing song can be arranged in a chiptune style defined more by choice of instrument and timbre than specific style elements.

Yamaha YM3812

The Yamaha YM3812, also known as the OPL2, is a sound chip created by Yamaha Corporation in 1985 and famous for its wide use in IBM PC-based sound cards such as the AdLib, Sound Blaster and Pro AudioSpectrum (8bit), as well as several arcade games by Nichibutsu, Toaplan and others.

The Ensoniq Mirage is one of the earliest affordable sampler-synths, introduced in 1984. As Ensoniq's first product, it became a best-seller. It was priced below US$1,700 with features previously only found on more expensive samplers like the Fairlight CMI.

Elektron SidStation

The Elektron SidStation is a musical synthesizer sound module, built around the MOS Technology SID mixed-mode synthesizer chip originally used in the Commodore 64 home computer. It was produced by the Swedish synthesizer company Elektron, and was introduced in 1999. As the SID chip had not been manufactured for years, Elektron allegedly bought up nearly all the remaining stock.

A rompler is an electronic music instrument that plays pre-fabricated sounds based on audio samples. In contrast to samplers, romplers do not record audio and have limited or no capability for generating original sounds. The term rompler is a portmanteau of the terms ROM and sampler. Both may have additional sound editing features, such as layering several waveforms and modulation with ADSR envelopes, filters and LFOs.

Ensoniq ESQ-1 61-key, velocity sensitive, eight-note polyphonic and multitimbral synthesizer

Ensoniq ESQ-1 is a 61-key, velocity sensitive, eight-note polyphonic and multitimbral synthesizer released by Ensoniq in 1985, marketed as a "digital wave synthesizer". Although its voice generation is typically subtractive in much the same fashion as most analog synthesizers that preceded it, its oscillators are neither voltage nor "digitally controlled", but provided by a custom Ensoniq wavetable chip. The signal path includes analog resonant low-pass filters and an analog amplifier.

HardSID

The HardSID is a family of sound cards, produced by a Hungarian company Hard Software and originally conceived by Téli Sándor.

Elektron is a Swedish developer and manufacturer of musical instruments founded in 1998, as well as having its headquarters, R&D and production in Gothenburg, Sweden. They produce mainly electronic musical instruments, but have also made effects units and software. Since 2012, there have been branch offices in Los Angeles and in Tokyo.

reSID is a reverse engineered software emulation of the MOS6581 SID chip programmed by Dag Lem. This chip was used in the Commodore 64 computer. reSID is free software, published under the GNU General Public License.

MOS Technology TED integrated circuit made by MOS Technology, Inc.

The 7360 Text Editing Device (TED) was an integrated circuit made by MOS Technology, Inc. It was a video chip that also contained sound generation hardware, DRAM refresh circuitry, interval timers, and keyboard input handling. It was designed for the Commodore Plus/4 and 16. Packaging consisted of a JEDEC-standard 48-pin DIP.

LMMS free software digital audio workstation

LMMS is a digital audio workstation application program. When LMMS is executed on a computer with appropriate hardware, it allows music to be produced by arranging samples, synthesizing sounds, playing on a MIDI keyboard, and combining the features of trackers and sequencers. It supports the Linux Audio Developer's Simple Plugin API (LADSPA) and Virtual Studio Technology (VST) plug-ins. It is free software, written in Qt and released under the GNU General Public License, version 2 (GPLv2).

The Korg DSS-1 is a 12-bit polyphonic sampling synthesizer released in September 1986. It came out at a time when many of the popular synthesizer companies were beginning to get into sampling, an area of sound design that had previously been left to a handful of fledgling companies such as Fairlight, E-mu, and Ensoniq. Like Yamaha and Casio, however, Korg did not stay long in the sampling arena. The DSS-1 was the company's only sampler until 1998 when Korg introduced sampling options on their Triton and Trinity series of workstations, and on their Electribe series of drum-and-phrase samplers.

A Bitcrusher is a lo-fi digital audio effect, which produces a distortion by the reduction of the resolution or bandwidth of digital audio data. The resulting quantization noise may produce a “warmer” sound impression, or a harsh one, depending on the amount of reduction.

A programmable sound generator, or PSG, is a sound chip that generates audio 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.

HVSC may refer to:

Robert Yannes is an American electronic engineer who designed the SID audio generator chip for the Commodore 64 and co-founded digital synthesizer company Ensoniq. He designed the Ensoniq 5503 Digital Oscillator Chip which was used in both commercial synthesizers and the Apple IIgs home computer.

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.

References

  1. Commodore Business Machines, Inc. (1982). "6581 Sound Interface Device (SID) Chip Specifications". Commodore 64 Programmer's Reference Guide (PDF) (1 ed.). Wayne, Pennsylvania: Commodore Business Machines, Inc. p. 457. ISBN   9780672220562. Archived (PDF) from the original on 2019-07-05. Retrieved 2019-07-05.
  2. Griggs, Brandon (2011-05-09). "The Commodore 64, that '80s computer icon, lives again". CNN . Archived from the original on 2019-07-04. Retrieved 2014-11-17.
  3. 1 2 Perry, Tekla S.; Wallich, Paul (March 1985). "Design case history: the Commodore 64" (PDF). IEEE Spectrum . IEEE. 22 (3): 48–58. doi:10.1109/MSPEC.1985.6370590. ISSN   0018-9235. Archived (PDF) from the original on 2019-07-04. Retrieved 2011-11-12.
  4. 1 2 3 4 5 6 Bagnall, Brian. On the Edge: The Spectacular Rise and Fall of Commodore (1 ed.). Winnipeg, Manitoba: Variant Press. ISBN   9780973864908.
  5. Horton, Kevin. "Remarked SID Chips Sold as New". SID. Archived from the original on 2019-07-04.[ unreliable source? ]
  6. 1 2 "6581 Sound Interface Device (SID)" (PDF). Commodore Semiconductor Group. October 1982. Archived (PDF) from the original on 2019-07-05. Retrieved 2019-05-07.
  7. Klose, Thorsten (2019-05-24). "MIDIbox SID V2 - User Manual". MIDIbox Projects. Archived from the original on 2019-07-04. Retrieved 2019-07-04.
  8. "New revolutionary C64 music routine unveiled". 1xn.org. 2008-11-04. Archived from the original on 2012-02-04.
  9. Mixer; SounDemoN; The Human Code Machine (2008-10-29). "Vicious Sid (2008)". Commodore 64 Scene Database. Archived from the original on 2019-07-04.
  10. Graham (2014). "SID 6581/8580 (Sound Interface Device) reference". 8 bit IC register reference. Oxyron. Archived from the original on 2019-07-04.
  11. Alstrup, Asger (2015-04-17). "Examination of SID noise waveform". SID - Sound & Music. Codebase64. Archived from the original on 2019-07-04.
  12. "Making Tracks: The Noble Art of Game Music". NEXT Generation . Vol. 1 no. 3. GP Publications Inc. March 1995. p. 49. ISSN   1078-9693.
  13. "The SID 6581/8580 Recordings Archive". jme. Archived from the original on 2019-07-04.
  14. "Stone Oakvalley's Authentic SID Collection (SOASC=)". Stone Oakvalley Studios. Archived from the original on 2019-07-04.
  15. "Unepic SID Channel".
  16. 1 2 "SID File Format Description" (TXT). High Voltage SID Collection. Archived from the original on 2019-07-05. Retrieved 2019-07-05.
  17. 1 2 kenchis. "Java SID Player Music Library V2". SourceForge. Archived from the original on 2019-07-05. Retrieved 2019-07-05.
  18. rolandh. "PSID64". SourceForge. Archived from the original on 2019-07-05. Retrieved 2019-07-05.
  19. Bauer, Christian. "SIDPlayer". Archived from the original on 2019-07-05. Retrieved 2019-07-05.
  20. Lankila, Antti. "JSIDPlay2: a cross-platform SID player and C64 emulator". Archived from the original on 2012-01-16.
  21. Latimer, Joey (August 1989). "Innovation Sound Standard". Compute! . Vol. 11 no. 111. p. 68. ISSN   0194-357X . Retrieved 2013-11-11.
  22. Replica Sound Cards - AdLib, Innovation SSI-2001, and SwinSID Ultimate. , retrieved 2019-08-01

Further reading