MOS Technology 6581

The MOS Technology 6581/8580 SID (Sound Interface Device) is the built-in programmable sound generator chip of the Commodore CBM-II, Commodore 64,^[1] Commodore 128, and MAX Machine home computers.

Together with the VIC-II graphics chip, the SID was instrumental in making the C64 the best-selling home computer in history,^[2] and is partly credited for initiating the demoscene.

Three separately programmable independent audio (able to produce 65,535 equally spaced frequencies on a linear scale, 0.06–3906.19 Hz range on a 1 MHz clock)

oscillators

Four distinct per audio oscillator (triangle, sawtooth, pulse, noise).^[10] Any combination of triangle, sawtooth, and pulse may be selected at the same time to produce additional waveforms.

waveforms

One multi mode 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 may be combined to produce additional timbres, for instance a notch-reject filter.

filter

Three attack/decay/sustain/release () volume envelope controls, one for each audio oscillator

ADSR

Three ^[10]

ring modulators

for each audio oscillator

Oscillator sync

Two analog-to-digital converters (typically used for game control paddles, but later also used for a mouse)

8-bit

External audio input (for sound mixing with external signal sources)

/modulation generator (via reading the state of the 3rd oscillator or 3rd envelope generator)

Random number

Remarking and forgery[edit]

Since 6581 and 8580 SID ICs are no longer produced, they have become highly sought after. In late 2007, various defective chips started appearing on eBay as supposedly "new".^[14] Some of these remarked SIDs have a defective filter, but some also have defective channels/noise generators, and some are completely dead. The remarked chips are assumed to either be factory rejects from back when the chip was still produced, or possibly "reject pulls" from one of the chip pulling operations that were used to supply the chips used in the HardSID cards.

Fake SID chips have also been supplied to unwitting buyers from unscrupulous manufacturers in China; the supplied chips are laser-etched with completely bogus markings, and the chip inside the package is not a SID at all.

Uses[edit]

Game audio[edit]

The majority of games produced for the Commodore 64 made use of the SID chip, with sounds ranging from simple clicks and beeps to complex musical extravaganzas or even entire digital audio tracks. Due to the technical mastery required to implement music on the chip, and its versatile features compared to other sound chips of the era, composers for the Commodore 64 have described the SID as a musical instrument in its own right.^[15] Most software did not use the full capabilities of SID, however, because the incorrect published specifications caused programmers to only use well-documented functionality. Some early software, by contrast, relied on the specifications, resulting in inaudible sound effects.^[3]

Well known composers of game music for this chip are Martin Galway, known for many titles, including Wizball, and Times of Lore, Rob Hubbard, known for titles such as ACE 2, Commando, Delta, International Karate, IK+, and Monty on the Run. Other noteworthies include Jeroen Tel (Cybernoid, Turbo Outrun, Robocop 3 and Myth), Ben Daglish (The Last Ninja, Jack the Nipper, Firelord, Gauntlet), David Dunn (Finders Keepers and Flight Path 737), David Whittaker (Speedball, BMX Simulator, Glider Rider) and Chris Hülsbeck (R-Type, Turrican and The Great Giana Sisters).

Recordings[edit]

The fact that many enthusiasts prefer the real chip sound over software emulators has led to several recording projects aiming to preserve the authentic sound of the SID chip for modern hardware.

The sid.oth4 project^[16] has over 380 songs of high quality MP3 available recorded on hardsid hardware and the SOASC= project^[17] has the entire High Voltage SID Collection (HVSC) released with 49 (over 35,000 songs) recorded from real Commodore 64s in a high quality MP3 file. Both projects emphasize the importance of preserving the authentic sound of the SID chip. In 2016, the Unepic Stoned High SID Collection (USHSC)^[18] was launched. It is a YouTube channel with over 50,000 SID tunes uploaded as single videos. The USHSC is based on both the SOASC= and HVSC, but also uploads recordings of recent SID music released at the Commodore Scene Database (CSDb) site. The channel features playlists containing roughly 5000 tunes each.

In 1989 on the Amiga computer, the demo "The 100 Most Remembered C64 Tunes" and later the PlaySID application was released, developed by and Ron Birk. This was one of the first attempts to emulate the SID in software only, and also introduced the file format for representing songs made on the C64 using the SID chip. This later spawned the creation of similar applications for other platforms as well as the creation of a community of people fascinated by SID music, resulting in The High Voltage SID Collection which contains over 57,000 SID tunes.

Per Håkan Sundell

Sound chip

MOS Technology VIC

POKEY

Original Amiga chipset#Paula

Chiptune

Collins, Karen (February 2006). . Soundscapes. 8.

""Loops and bloops": Music of the Commodore 64 games"

Cass, Stephen (July 15, 2019). . IEEE Spectrum. Archived from the original on July 20, 2019.