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SID internals documentation

Reverse-engineering of the MOS 6581/8580 SID schematics by Leandro Nini and ttlworks, based on silicon layouts photographed by Michael Huth and revectorized and annotated by Tommi Lempinen

Control Logic

• Clock
• Reset
• Address Decoders
• Data Bus
• Registers

Waveform Generator

• Oscillator
• Pulse Waveform
• Triangle Waveform
• Noise Generator
• Wave Selector

Envelope Generator

• Envelope Overview
• Envelope Counter
• Sustain Comparator
• ADSR registers
• Counter Logic
• Exponential Divider
• LFSR15 counter
• LFSR5 counter

Analog Stage

• Analog stage overview
• 6581 DACs
• 6581 Opamps
• 6581 Filter overview
• 6581 Audio output
• 8580 DACs
• 8580 Virtual ground
• 8580 AC Voltage divider
• 8580 Opamps
• 8580 Filter overview

Paddles

• Paddles Overview
• Paddle counter
• POT registers

External Filter

• External filter

References

• Die shots: http://retronn.de/imports/commodore_chips.html
• Original layouts: http://oms.wmhost.com/misc/
• Reverse-engineering discussion: http://forum.6502.org/viewtopic.php?f=8&t=4150