SID

From C64-Wiki

This article is under construction and classified as "work in progress" !!!

The shortcut SID means Sound Interface Device and is the name of a chip inside the computers VC 10, C64 and C128. The SID generates tones and noises and was developed by Bob Yannes, who was a employee of the firm MOS Technology. Bob (Robert) Yannes knows, beside technical know-how, a lot of music. His intention was to implement a real substractive synthesis chip, totally different from all other sound devices of that time. It's distinctive sound is easily recognized and it was clearly ahead the competition at it's time. The chip combines analog and digital circuitry and even today it is not possible to emulate it's sound to 100%, although an emulated sound is coming very close to the original and a layperson won't notice the differene. The SID sound is well known among retro gamers. A collection that includes nearly every song ever written for the chip is available as the High Voltage SID Collection.

In the C64 prototype the model SID 6581 was used. In newer models like C64-II or the C128, the newer version called SID 8580 was used. The SID can be easy programmed in BASIC or machine language like Assembler.

Properties of the SID:

3 tone generators (voices), frequency 0-4 kHz (16 Bit decomposition)
4 forms of waves (sawtooth, triangle, rectangle pulse width modulation , (white) noise /rush)
3 amplitude modulator, until 48 dB
3 envelope generators
Synchronization of the oscillators
Ring modulation
Programmable filters (low pass, bandpass, high pass, notchfilter?)
Audibleness into 16 steps
2 A/D-converter (8 bit, low freuqent, used for reading paddle input)
Random generator
Audio input (cannot be used for sampling, but the signal can be routed through the SID filter)

1 SID, MIDI & Co
2 Memory Adresses of the SID
3 Trivia
4 Links

[edit] SID, MIDI & Co

Back in the 1980s it was still a great (and expensive) novelty using computers in recording studios. These computers were used to either control equipment or sequence MIDI. It was only by the end of the decade when computers were used to synthesise sounds professionally for record.

Although PCs, Atari STs, Apples and Amigas could be happily used to power both domestic and professional set-ups, machines of lesser creedence like the C64 and Sinclair Spectrum 128 could also be employed for MIDI duties.

The Commodore 64 would have been a splendid little home studio number-cruncher in, say, 1987 when computer music really started to get into the flow. A budding young Gary Numan could easily use his Portastudio, MIDI-enabled C64 and MIDI synthesiser together (by use of a synchroniser) to give himself an impressive multi-track MIDI bedroom studio. And use the SID itself to give him even more funky sounds when recording extra tracks to his tape.

A whole raft of music software was (and still is) being made for the C64, along with hardware to go with them.

Commodore 64s, along with VST emulators, are still very handy for some retro enthusiasts. Various composers, synthesisers and sequencers can still be used to compose and record musical pieces, which can be expanded even further when used with more modern computerised equipment. Here is an example of one particular home composer: http://www.concept-single.net/

However, it finally looks as if the C64 has made it as a recording tool in its own right in persuance of commercial music release. One such C64 music shop can be found here: http://www.c64audio.com/

[edit] Memory Adresses of the SID

Template:Translated 1st Nov 09 from German to English

54272 Frequency voice 1 (Low-byte)
54273 Frequency voice 1 (High-byte)
54274 Duration voice 1 for square (Low-byte)
54275 Duration voice 1 for square (High-byte 0...15)
54276 Waveform voice 1 (Noise 129; Square 65; Sawtooth 33; Triangle 17)
54277 Attack (0*16 aggressive ... 15*16 subtle) / decay voice 1 (+ 0 aggressive ... 15 subtle)
54278 Sustain (0*16 silent ... 15*16 loud) / release voice 1 (+ 0 fast ... 15 slow)
54279 Frequency voice 2 (Low-byte)
54280 Frequency voice 2 (High-byte)
54281 Duration voice 2 for square (Low-byte)
54282 Duration voice 2 for square (High-byte; 0...15)
54283 Waveform voice 2 (Noise 129; Square 65; Sawtooth 33; Triangle 17)
54284 Attack (0*16 aggressive ... 15*16 subtle)/ decay voice 2 (+ 0 aggressive ... 15 subtle)
54285 Sustain (0*16 silent ... 15*16 loud)/ release voice 2 (+ 0 fast ... 15 slow)
54286 Frequency voice 3 (Low-byte)
54287 Frequency voice 3 (High-byte)
54288 Duration voice 3 for square (Low-Byte)
54289 Duration voice 3 for square (High-Byte 0...15)
54290 Waveform voice 3 (Noise 129; Square 65; Sawtooth 33; Triangle 17)
54291 Attack (0*16 aggressive ... 15*16 subtle) / decay voice 3 (+ 0 aggressive ... 15 subtle)
54292 Sustain (0*16 silent ... 15*16 loud) / release voice 3 (+ 0 fast ... 15 slow)
53293 Filter cutoff frequency (Low-byte 0...7)
53294 Filter cutoff frequency (High-byte)
53295 Resonance; 0 none; 15*16 strong; (+ filter for 1-voice 1; 2-voice 2; 3-voice 4; extern 8)
54296 Volume for all voices; 0 silent; 15 loud; (+ filtermodus 3-voice off 128; high-pass 64; band-pass 32; low-pass 16)
54297 Paddle X-value
54298 Paddle Y-value
54299 Oscillator voice 3
54300 Envelope voice 3
54528-55295 SID-registers

[edit] Trivia

Bob Yannes later went on to form the well known synthesizer company Ensoniq. Their first product, the ESQ-1 synthesizer is, according to Bob, the synthesizer he wanted the SID chip to be. Due to a rough time table, a lot of features had to be dropped and the design was finished just in time. Many characteristics of the SID sound are bugs, techically seen, but depending on the point of the listener they can be seen as features or were used to hack the chip. For example the volume register design flaw in the original 6581 chip was used to play back samples. Everytime the volume register value was altered, an audible click could be heard. By changing the first 4 bits of the register at $D418 fast enough, samples can be played back with rates up to some kHz (depends on the code and whatelse uses rastertime) with 4 bit resolution. In the later 8580 model this "bug" was fixed and samples were inaudible, but it is possible to revert this by soldering a 470k resistor and a 1M pot in series between EXT IN and GND. Even better sample playback can be achieved by altering the pulse width modulation register, which can hold an eight bit value.