SID is the name of the Commodore 64 sound chip. It is a full synthesizer with three oscillators and a resonant filter, packaged inside a 28pin wide DIP package chip. While the mail way to find such chips is to cannibalize an old Commodore computer, there have been other sources as well. I have now a total of five such chips.
There have been two versions 6581 and 8580. The 6581 is considered having better filters.
Beware of the fact that there are fake SID chips on the loose. If you want to get yours, be sure it is a genuine, working SID.
My approach to building a SID Synth is through the MIDIBox SID implementation
Analytical specs of the SID chip
- three separately programmable independent audio oscillators (8 octave range, approximately 16 – 4000 Hz)
- four different waveforms per audio oscillator (sawtooth, triangle, pulse, noise)
- one multi mode filter featuring low-pass, high-pass and band-pass outputs with 6 dB/oct (bandpass) or 12 dB/octave (lowpass/highpass) rolloff. The different filter-modes are sometimes combined to produce additional timbres, for instance a notch-reject filter.
- three attack/decay/sustain/release (ADSR) volume controls, one for each audio oscillator.
- three ring modulators.
- oscillator sync for each audio oscillator.
- two 8-bit A/D converters (typically used for game control paddles, but later also used for a mouse)
- external audio input (for sound mixing with external signal sources)
- random number/modulation generator
The core SID has been built in A working SID Synth and in Sowing the SIDs of love
and the packaging project is where we cannibalize the laughtop and where we see if the screen fits
You will see many implementations using the original C64 casing like this one by SubAtomicGlue
Stay tuned!
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