Most home computers of the early 1980s could beep, buzz or hiss. The Commodore 64 could play music, because the engineer who designed its sound chip was a synthesiser player who thought the other chips were not good enough. “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,” Bob Yannes said in 1996. The chip he designed instead, the 6581 SID, gave three voices the controls of a real synthesiser: envelopes, several waveforms and a filter. It took him four or five months, and its sound became the sound of the Commodore 64.
A hobbyist at MOS
Yannes came to MOS Technology, Commodore’s chip-making subsidiary in Pennsylvania, straight from college. Tim Danton’s history of the period says he met Al Charpentier, who ran chip design there, while still a student, built his final-year project around MOS’s new video chip, and was hired in July 1979. He had been an electronic music hobbyist since school, and he said later that this was part of the reason he was hired: “my knowledge of music synthesis was deemed valuable for future MOS/Commodore products.”
Michael Tomczyk, Jack Tramiel’s assistant, met the team in May 1980, when they were finishing the 22-column VIC video chip. He described Yannes as “a light-featured, 23-year-old chip designer who did most of the work on the chip”, who “looked about thirteen and was constantly being kidded about his youthful appearance.”
The first VIC-20
The VIC chip had been offered to other manufacturers, and had found no buyers. Yannes decided to show what it could do. According to IEEE Spectrum, he “had designed the VIC-20 at home, from a spare prototype board.” When Tramiel wanted a cheap colour computer to show at the Consumer Electronics Show in June 1980, Yannes went with it. Tomczyk was there:
Yannes spent a marathon week of all-night engineering sessions to put together a computer we could show at CES. The result was nicer-looking than most people expected, especially considering it was a Frankenstein monster thrown together from old spare parts and obsolete products that Yannes literally cut apart and put together in a different form.
Engineers from Commodore’s systems group in California brought a rival prototype of their own. Tomczyk adds that Yannes had only built his to prove the machine could be done, and was “eager to get back to designing computer chips”. The VIC-20 that went on sale was finished by other engineers, but it began on his bench.
Designing the SID
In January 1981 the MOS engineers started work on a new graphics chip and a new sound chip, with no particular computer in mind. Yannes took the sound chip. “I’d worked with synthesizers, and I wanted a chip that was a music synthesizer,” he told IEEE Spectrum. The trouble with game sound, he explained, was the envelope: “With most of the sound effects in games, there is either full volume or no volume at all. That really makes music impossible.”
The SID’s answer was to give each of its three voices the parts of an analogue synthesiser: an oscillator with four waveforms, an envelope that shapes each note’s attack, decay, sustain and release, and a shared filter that can be swept while a note plays. Compute! listed “16-bit frequency resolution over a nine-octave range” and “programmable high-, low-, band-, and notch-pass filters”. “The SID chip is basically a synthesizer on a chip,” Yannes told the magazine in January 1983. “I played with synthesizers for years, so I’m quite familiar with them.”
Parts of the design were compromises, and Yannes said which ones:
- Three voices, not one. Commodore had asked only for a “sound chip”. Yannes would have liked the three oscillators to work together as one rich voice, but “I had to put separate envelope controls for each oscillator … in order to satisfy the video game/sound effects marketing demands.” That is why the three voices have their own envelopes but share a single volume control.
- The filter came last. “The filter was the last thing that was worked on,” he told IEEE Spectrum. “I ran out of time.” In 1996 he called it “the worst part of SID because I could not create high-gain op-amps in NMOS, which were essential to a resonant filter.”
- An input for a fourth voice. An external audio line lets another sound source pass through the SID’s filter and volume control. “Tape recorders, radios, electric guitars, even another SID chip,” he said. He designed it as a standard 6502 peripheral chip, and pictured several SIDs chained in a cartridge.
The design, he told IEEE Spectrum, “took only about four or five months”, built on research “which I’d been doing since high school”. The whole schedule for the chips and the computer was, in his words from 1996, “incredibly tight (some would say impossibly tight)”. Commodore Magazine put its own spin on the result in December 1982, claiming that Yannes “took a commercial $750 synthesizer and put every one of its functions on one chip”.
Once the chips worked, Tramiel decided at the end of 1981 to build them into a 64K computer, and the Commodore 64 was shown in January 1982. IEEE Spectrum described Yannes as both the sound-chip designer and the C64’s systems architect. He had not planned for the machine’s BASIC to control his chip: “there was never any intention that the system would have built-in software to control the graphics or the sound.” Owners who wanted music had to write numbers straight into the SID’s registers. The game composers who learned to do that well, such as Rob Hubbard, are the reason the chip is still remembered.
Peripheral Visions and Ensoniq
Yannes did not stay to see that happen. Compute!’s January 1983 issue reported that he had “recently left Commodore to form his own company, Peripheral Visions, Inc.” IEEE Spectrum’s account, written two years later, puts the departure of the whole C64 design team, Charpentier and Yannes included, in the spring of 1983; Yannes had evidently gone a little ahead of the others. Yannes told Compute! what he hoped to do next: “There’s no reason we can’t take music systems being sold now for $4000 and bring them out for consumers for around $400 or $500.” He added: “I pretty much got the features that I wanted out of the SID chip in the 64, but not the performance I wanted.”
Peripheral Visions was renamed Ensoniq, and its first product was a musical instrument. In January 1985 Compute! reported the Ensoniq Mirage, a sampling keyboard at $1,700 made by “some of the engineers who designed the Commodore 64”, with “Mirage designer Yannes” explaining that a new custom chip kept its price down. It could record a sound, a violin or a barking dog, and play it back across the keyboard. The article compared it with a Kurzweil sampling keyboard that cost $10,795. Ensoniq’s sound chips reached computers too: Apple’s 1986 introduction to the Apple IIGS describes its Digital Oscillator Chip as “made by Ensoniq and used in their line of music synthesizers”.
Sources
- Tekla S. Perry and Paul Wallich, “Design case history: the Commodore 64”, IEEE Spectrum, vol. 22 no. 3, March 1985 (read in the version republished at spectrum.ieee.org): Yannes joining MOS in 1979 and building the VIC-20 prototype at home; the chip project from January 1981; “I’d worked with synthesizers”; “full volume or no volume at all”; the four-or-five-month design; the filter and “I ran out of time”; systems architect of the C64; no built-in software for graphics or sound; the team’s departure in spring 1983 and the renaming of Peripheral Visions as Ensoniq.
- Tim Danton, The Computers That Made Britain (Raspberry Pi Press, 2021), chapter on the Commodore VIC-20: MOS’s VIC chip finding no buyers; Yannes meeting Charpentier as a student and being hired in July 1979.
- Retro Gamer issue 46, 2008, VIC-20 feature: the VIC chip offered for sale to arcade manufacturers without success; Yannes’s prototype built from spare PET parts.
- Michael S. Tomczyk, The Home Computer Wars: An Insider’s Account of Commodore and Jack Tramiel (Compute! Publications, 1984): Yannes at 23 and the VIC chip (p. 79); the June 1980 CES prototype (p. 113).
- Tom R. Halfhill, feature on computer music, Compute! issue 32, January 1983, pp. 26–33: “basically a synthesizer on a chip”; the SID’s specification; separate envelopes for marketing reasons; the external input and chaining SIDs; Yannes having left to form Peripheral Visions; the $4000 and “not the performance I wanted” quotes.
- Compute! issue 56, January 1985, p. 34: Ensoniq and the Mirage, $1,700; the Kurzweil at $10,795; Yannes as the Mirage’s designer.
- Compute!’s Gazette issue 11, May 1984, pp. 18–19: Yannes, “who has worked with synthesizers for years and now runs his own electronic design company, Peripheral Visions”.
- Commodore Magazine, vol. 3 no. 6, December 1982, p. 8: the “$750 synthesizer” description. Vol. 3 no. 2, April 1982, p. 104: “Unsung Heroes”, naming Yannes in Commodore’s research and development group.
- Apple Computer, Technical Introduction to the Apple IIGS (1986): the Digital Oscillator Chip “made by Ensoniq”.
- Andreas Varga, “Interview with Bob Yannes”, by e-mail, August 1996 (web, secondary): the sound chips “designed by people who knew nothing about music”; his hobby and why MOS hired him; the “impossibly tight” schedule; the filter and the NMOS op-amps. https://landley.net/history/mirror/commodore/yannes.html