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Commodore 64 SID chip




commodore amiga500

infoCountry: USA
Weight : 1,8 Kg
Dimensions (classic): 40,4 x 21.6 x 7,5 cm
audio demo trend price : 50€
manual schematics comments

AUDIO CHIP MOS 6581 / 8580
for Commodore 64

The DIS audio chip was implemented into the commodore 64, all-time best seller . Sid is considered like a true synthesizer.

infoThe purpose of this page is not the CBM64 itself as we focus only to SOUND and MUSIC applications related to the retro computer world.

mos 6581
commodore 64 box

info C64 / VIC64 HOME COMPUTER the main panel features a brown keyboard (66 keys) but no numeric pad.
Terminal connectors:
- cartridge slot
- TV connector (HF-Modulator- analog)
- audio/video DIN connector
- serial bus (generally for disk drive)
- cassette interface 12 pins
- user port
- joystick (x2) 9-pins Atari type

ac Power supply is an external custom PSU (9V AC / +5V DC).



editOVERVIEW CMB64 is based on a 8 -bits MOS 6510 CPU (about 1 MHz) derived from previous 6502 also can be an optimized MOS 8500. Graphic interface is managed by a 16 colors VIC-II (video interface chip at 320x200 pixels) MOS 6559 for PAL system.

MOS 6510

editSOUND CHIP the SID (Sound Interface Device) a 28-pin DIP capsule audio chip was projected in 1982 by Robert Yannes (who worked for the Ensoniq Mirage sampler) for the American 8-bits computer Commodore 64 then revamped model C128. The SID chip is a mixture of digital and analogue technology with phase accumulated oscillators and analogue multimode NMOS filter.

commodore 64 motherboard

There are 2 main SID versions:

- MOS 6581

- MOS 8580 (for updated c64 boards)

edit click to enlarge pic

edit SID SYNTH DETAILS SID generates 3 channels or oscillators (5 shapes: triangle, saw, mixed, noise, pulse variable width) with variable parameters:

- ringmodulator: an oscillator modulates the previous one e.g: 3>2 - 2>1 - 1>3
- pitch detune
- hardsynch
- transpose
- delay start
- PWM (variable width)

mos 6581

SID REVISIONS the 6581 was used on first commodore 64 from 1982 to 1986 with 4 main revisions (called "R1" "R2" [...] new updated C64 used the 8580 technically compatible with softwares but they did sound different mainly for filter structure.
TIP: modern SWINSID hardware replacement with new features.

mos 6581



edit FILTER multimode resonant filter with cutoff range from 30 Hz to 12 kHz:


- lowpass at 2 poles
- bandpass at 1 pole
- highpass at 2 poles
- band reject at 1 pole

editThe Cbm 64 filters external sources using the audio/video DIN connector.


adsr ENVELOPE 4 EGs, 4 stages ADSR structure :

c64 audio

- EG1 OSC1 amp

- EG2 OSC2 amp

- EG3 OSC3 amp

- EG4 VCF filter


lfo LFO up to 4 bipolar delayed assignable modulators with fade-in, variable depth.

c64 audio

edit The modulators are identical and features 7 shapes; in addition 2 LFO can be combined for more complex waveforms.


MEMORY 64 Kb Ram (8 X soldered IC 4116) - data can be saved usually to custom tape device or 5¼" disk drive like CBM1541 but some moderns geek stuff managed to add custom hard disk, usb drive, flash memory and more.

tape usb

edit OS
is basically composed by 3 EPROM:



- 901227-3 KERNAL
- 901226-01 BASIC
- 901225-1 Characters map.

edit Audio and music hardware some musical third part societies developed some hardware able to exploit internal SID or other sonic technologies from this era.

roland tr505

Audio expansion module:

- Siel Sound Buggy
- SFX sound expander based on FM synthesis VIDEO


speech processor (hardware)

- magic voice VIDEO
- currah VIDEO
- voice messenger
- voice command module
- votalker VIDEO

edit Special Commodore 64 Impossibile Mission speech page

mode machine sid sound sampler

siel midi cbm64 Midi interface and keyboard




roland tr505

Commodore 64 main model series:
- 64C white (new board with new sid)
- 128 a new computer with cbm64 mode
- SX64 a portable C64 in a suitcase and monitor

sidstation Elektron Sidstation A Midi commercial module based on MOS sid
mode machine sid

MODE MACHINE SID 8-Bit Desktop Synthesizer & Groove Box with emulated SID or slot for genuine SID VIDEO

Twisted electrons Therapdsid is a commercial SID clone with some controls VIDEO

customcoomodore 64

MODDED various CBM64 have been customized with audio enhancements like 2 sids , realtime functions and more


commodore 64 vst Commodore SID VST instruments softwares: too many! - pure 6581, Delamancha, REFX, 38911 Bytes, tony bytes bleep, dream 64 and countless samples collections.



brochure commodore 64 ugly
brochure brochure brochure
ad ad cool c64 girls ad weird ad
brochure commodore 64 girl commodore 64 big commodore sid commodore sid
ugly: ugly too     marcel the cat

Company: Commodore
Model: CMB64
Class: Computer
Dates: 1982
Technology: Hybrid
Synthesis: subtractive
Polyphony: 3 voices
Multitimbric: 3 parts
Oscillator: 3 OSC
Hardsynch: yes
Ringmodulator: yes
Filter: Static Low pass
LFO: 4 modulators
Filter: LPF / HPF / BPF
Envelope: 4 EG
Memory: 64 kb (basic)
Midi: optional
CPU: 6510
IC: MOS 6581 / 8580

PSU: external








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REVIEW : "Sid is something incredible, a cheap but great synthesizer for the mass: the music will never play 2 times the same way! "

manual manual
-classic - time reliability
- lot of good game music
- obsolete

TECH: all data and IC are based on my Assy rev.C PAL 1983.




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Commodore 64 5.0 out of 5 based on 1 ratings. price €50