thumb|MOS Technology SIDs. The left chip is a 6581. The right chip is an 8580. CSG stands for Commodore Semiconductor Group. The numbers 3884 and 0692 are in WWYY form, i.e. the chips were produced week 38 of 1984 and week 06 of 1992. 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 the Commodore 64, Commodore CBM-II, Commodore 128, and MAX Machine home computers. Together with the VIC-II graphics chip, the SID was instrumental in making the C64 the best-selling home computer in history, and is partly credited for initiating the demoscene.
The SID was an advanced design for the era, compared to competing sound chips like Atari's POKEY or the widely used General Instrument AY-3-8910 and Texas Instruments SN76489. In contrast to those chips, which were aimed at producing simple sound effects and music for games and similar purposes, the SID is better described as a single-chip music synthesizer. It included common synthesizer features like ADSR envelope controls, the ability to modulate channels with each other, and filters. These features allowed the SID to produce more complex sounds and music than other home computers of the time.
The original version of the SID, the 6581, was introduced with the C64 in 1982. It had a number of design features that were not well implemented due to time constraints, which resulted in various oddities in the output. Many of these were addressed in the later 8580 revision (sometimes labelled 6582), which took over from the original 6581 around 1986 and was used in later machines. The 8580 was produced until around 1992.
In the spring of 1983, the designer of the SID, Bob Yannes, left Commodore and would later go on to produce digital synthesizers at his new company, Ensoniq.
History
The SID was devised by engineer 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.