MOS Technology 6581

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.