AUDIO CHIP MOS 6581 / 8580
for Commodore 64 (1982)

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

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

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

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

 

 

OVERVIEW 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.

SOUND 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.

There are 2 main SID versions: - MOS 6581 - MOS 8580 (for updated c64 boards) click to enlarge pic

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)

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.

 

 

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

 

ENVELOPE 4 EGs, 4 stages ADSR structure :

- EG1 OSC1 amp - EG2 OSC2 amp - EG3 OSC3 amp - EG4 VCF filter

 

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

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.

OS is basically composed by 3 EPROM:

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

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

	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 Special Commodore 64 Impossibile Mission speech page
	sound sampler - SFX VIDEO
	Midi interface and keyboard

 

 

RELATED FAMILY:

	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
	Elektron Sidstation A Midi commercial module based on MOS 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
	MODDED various CBM64 have been customized with audio enhancements like 2 sids , realtime functions and more VARIOUS HARDWARE Other DIY projects like SAMMICH, HARDSID USB ucapps.de
	Commodore SID VST instruments softwares: too many! - pure 6581, Delamancha, REFX, 38911 Bytes, tony bytes bleep, dream 64 and countless samples collections.

 

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