SID Chip

The SID gave the Commodore 64 its voice. Designed by Bob Yannes at MOS Technology, it was closer to a real synthesizer than any other sound chip in a home computer of its day.

What it can do

• Three voices, each with its own pitch

• Four waveforms: triangle, sawtooth, pulse and noise

• An envelope on every voice: attack, decay, sustain and release

• A filter that can sweep a sound from bright to muffled

Two versions

The original 6581 has a warm, gritty filter that varies from chip to chip. The later 8580 runs at a lower voltage and sounds cleaner. Musicians still argue over which one is better.

Afterlife

Bob Yannes went on to co-found Ensoniq, the synthesizer maker. SID music is still written today, and the C64 Ultimate has sockets for two real SID chips plus eight more recreated inside its FPGA.