SID

# SID - Sound Interface Device ## The Chip That Sang The MOS Technology 6581/8580 SID (Sound Interface Device) is arguably the most famous sound chip in computing history. Designed by Bob Yannes, who later founded Ensoniq, the SID brought analog synthesizer capabilities to the Commodore 64. ## Technical Details ### Three Independent Voices Each voice features: - Frequency control (0-4kHz) - Four waveforms: Triangle, Sawtooth, Pulse (with PWM), and Noise - ADSR envelope generator - Individual on/off control ### Advanced Features - Ring modulation between voices - Hard sync between oscillators - Analog filter (low-pass, band-pass, high-pass) - External audio input mixing ### Register Map The SID occupies 29 registers at $D400-$D41C: - Voice 1: $D400-$D406 - Voice 2: $D407-$D40D - Voice 3: $D40E-$D414 - Filter: $D415-$D418 - Miscellaneous: $D419-$D41C ## The Two Versions ### 6581 (Original) - Warmer, fuller sound - Filter varies between chips - Produced 1982-1989 ### 8580 (Revised) - Cleaner, more consistent - Better filter tracking - Fixed sample playback bug - Produced 1989-1993 ## Musical Legacy The SID's unique sound influenced electronic music far beyond the Commodore 64. Artists continue to use SID sounds in modern productions, and the chiptune genre owes much to its distinctive voice.