Difference between revisions of "6581"

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The '''''Sound Interface Device (SID)''''' is an analog synthesizer chip designed by Robert "Bob" Yannes for the [[Commodore 64]]. It is also found on the [[Commodore 128]] and the [[SSI 2001]].
+
The '''''Sound Interface Device (SID)''''' is an analog synthesizer chip designed by Robert "Bob" Yannes as part of the [[Commodore 64]] computer. It came in two ''models'', 6581 and 8580.
  
SID contains 3 voices with 4 selectable waveforms and an ADSR envelope each. The duty cycle of each pulse wave can be set with a precision of 0.0244140625%. The triangle and pulse wave can be combined (known as $51) to form a slap bass. Also ring modulation on triangle waves and Hard Sync are supported. Changing waveforms rapidly provides for thumping drums.
+
In the 1970s, Yannes was influenced by the synthesizer solo at the end of ''Lucky Man'' by [[Emerson, Lake and Palmer]] and had all albums by [[Kraftwerk]] and [[Mike Oldfield]]. In 1981, aged 24, he was tasked with designing a sound chip, with a given size, in only 4 or 5 months. Yannes thought that the audio designers of the [[TIA]], [[SN76489]], [[AY-3-8914]] and [[POKEY]] chips knew nothing about music. He wanted to design a professional synthesizer and fulfilled 70% of his own wish list. Unfortunately for musicians, the schedule left serious bugs and inconsistencies.
  
Changing the master volume and toggling the filter produces a click; the greater the change, the louder. A very few programmers worked around it by changing the volume gradually rather than at once. On the upside, it allows to play 4-bit PCM samples, unforgettably the speech in ''Impossible Mission (C64)''. In the late 1980s, it was very popular to play digi drums over SID voices. However, samples on SID are always very CPU-intensive.
+
Besides sound, SID also tracks movements of connected mice or paddles and was often used as a random number generator, so if you remove the sound chip from a Commodore computer, some games may not work properly.
  
The SID chip is clocked at the same frequency as the C64's or C128's CPU. Since this frequency differs in NTSC and PAL regions, music is detuned if played at the wrong clock. Also, almost all C64 and C128 sound drivers are hooked to the screen refresh rate, which differs even more, so if a note is released early, it may get cut off.
+
==Channels==
 +
On each of 3 voices, you can choose:
 +
* '''Pitch''' up to 3848 Hz (A♯7) in 0.06 steps. This precision, especially in higher pitches, was new at the time.
 +
* [[Sound Wave#Envelopes|'''ADSR''']]. Due to aforementioned bugs, some notes may be delayed slightly, but audibly for musicians. The volume cannot be directly set, which [[Charles Callet]] criticized.
 +
* '''Waveform''': [[Sound Wave#Triangle Wave|triangle]], [[Sound Wave#Sawtooth Wave|sawtooth]], [[Sound Wave#Pulse Wave|pulse]], [[Sound Wave#White Noise|noise]], or combinations of the first three (with differences per model). The combined triangle and pulse resembles a guitar or slap bass.
 +
** '''Duty cycle''' of each pulse-based wave in 0.0244140625% steps.
 +
** Whether to use [[Sound Wave#Ring Modulation|'''ring modulation''']] on triangle-based waves.
 +
** Whether to use [[Sound Wave#Hard Sync|'''Hard Sync''']].
 +
* Whether to use the single [[Sound Wave#Filters|'''filter''']].
  
A single low-pass, band-pass, high-pass or band-reject filter can be applied to any combination of voices. A resonance from 0 to 15 and a cutoff frequency from 0 to 2047 can be chosen. Unfortunately, these values are not in any standard like Hz; worse even, due to a production shortcoming, they vary with every SID chip and even every computer it is socketed on. As a result, gamers often heard sections muffled or louder than intended. Most composers, including [[Rob Hubbard]], [[Martin Galway]], [[Chris Hülsbeck]], [[Jeroen Tel]] and even SID creator Yannes expressed their concern in interviews, and some, like [[Ben Daglish]], [[Fred Gray]] and [[Chris Grigg]], used the filter very sparingly or purposely avoided it.
+
Percussion was initially made using one noise, but from 1985 to 1987, [[Rob Hubbard (C64 Driver)|Rob Hubbard]] and [[We M.U.S.I.C.]] pioneered rapidly switching waveform for more thumping percussion. However, it was somewhat lacking compared to the "deep" percussion of [[POKEY]] or [[AY-3-8910|AY]] chips, and some C64 composers like [[Adam Gilmore]] have expressed their concerns about it.
  
Besides sound, SID also provides the potentiometers of connected mice or paddles. The current signal and volume of voice 3 can be read back. The signal of the noise was commonly used for random number generators, and the volume was sometimes written back to a modulatable register, usually the cutoff frequency.
+
One single [[Sound Wave#Filters|low-pass, band-pass, high-pass or band-reject filter]] can be applied to any combination of voices. A resonance from 0 to 15 and a cutoff frequency from 0 to 2047 can be chosen. Unfortunately, these values are not in any standard like Hz; worse even, they vary with every SID chip and even every computer it is socketed on. As a result, gamers often heard sections muffled or louder than intended. Most composers, including [[Rob Hubbard]], [[Martin Galway]], [[Chris Hülsbeck]], [[Jeroen Tel]] and Yannes expressed their concern in interviews, and some, like [[Ben Daglish]], [[Fred Gray]] and [[Chris Grigg]], used the filter very sparingly or purposely avoided it. A very few games allow the gamer to alter the games' filter settings.
  
In 1986, a major revision, known as 8580, appeared. The $51 waveform sounds a bit fuller, more waveforms can be combined and the filter is consistent, but samples have become very quiet or even mute. The latter could be regained by soldering a resistor, but later, other methods of playing samples were discovered.
+
Both SID models can play samples in different ways, unforgettably the speech in ''Impossible Mission (C64)''. However, samples are always very CPU-intensive, around 6000 Hz and usually limited to title screens.
 +
 
 +
The current output of voice 3 can be read back: Noise was often used as random number generator, and the ADSR output was sometimes written back to modulatable registers, usually the cutoff frequency.
 +
 
 +
==Versions==
 +
===6581===
 +
The slap bass sounds thin, and other combined waves very quiet.
 +
 
 +
Changing SID's master volume and toggling the filter produce a click; the greater the change, the louder. A very few people worked around it by changing the volume gradually rather than at once. When they wanted to turn the filter off, they actually left it on and instead set the cutoff frequency to a bound where it made the least difference.
 +
 
 +
On the upside, clicks allow to play unsigned 4-bit [[Pulse code modulation|PCM]] samples on a 4th voice. In the late 1980s, it was very popular to play digi drums over 3 SID voices.
 +
 
 +
===8580===
 +
In 1986, when Yannes had long left, the only major revision of SID appeared. It started prevailing in the early 1990s.
 +
 
 +
The slap bass sounds fuller and other combined waves much louder.
 +
 
 +
The filter is consistent, but the lowest possible cutoff frequency is mute, hence some songs arranged for 6581 sound choppy on 8580. In turn, 8580 songs buzz and click annoyingly on 6581.
 +
 
 +
Clicks, and therewith the 4th voice, are quiet or even mute. This can be fixed by soldering a resistor, but by 1997, methods to reliably play samples ''replacing'' one of the 3 SID voices were becoming more popular.
 +
 
 +
===Examples===
 +
This section demonstrates the above differences using recordings from up to 4 real C64s (labelled R2, R3, R4 and R5) by [https://www.6581-8580.com/ Stone Oakvalley's Authentic SID Collection (SOASC=)]:
 +
 
 +
{| class="wikitable"
 +
! Feature
 +
! Song
 +
! Game
 +
! 6581 recording
 +
! 8580 recording
 +
|-
 +
| 4th voice
 +
| [[Title - Cobra (ZXS)#Arkanoid (C64)|Theme]]
 +
| [[Arkanoid (C64)]]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/055/MP3/MUSICIANS/G/Galway_Martin/Arkanoid_T001.sid_MOS6581R2.mp3 R2]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/055/MP3/MUSICIANS/G/Galway_Martin/Arkanoid_T001.sid_CSG8580R5.mp3 R5]
 +
|-
 +
| Slap bass
 +
| [[Underground - Labyrinth: The Computer Game#Labyrinth: The Computer Game (C64)|Underground]]
 +
| [[Labyrinth: The Computer Game (C64)]]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/064/MP3/GAMES/G-L/Labyrinth_T001.sid_MOS6581R2.mp3 R2]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/064/MP3/GAMES/G-L/Labyrinth_T001.sid_CSG8580R5.mp3 R5]
 +
|-
 +
| Other combined waves
 +
| [[Impossible Mission II Theme#Impossible Mission II (C64)|Theme]]
 +
| [[Impossible Mission II (C64)]]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/057/MP3/GAMES/G-L/Impossible_Mission_II_T001.sid_MOS6581R2.mp3 R2]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/057/MP3/GAMES/G-L/Impossible_Mission_II_T001.sid_CSG8580R5.mp3 R5]
 +
|-
 +
| Filter minimum
 +
| [[Main Menu - The Great Giana Sisters#The Great Giana Sisters (C64)|Main Menu]]
 +
| [[The Great Giana Sisters (C64)]]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/049/MP3/MUSICIANS/H/Huelsbeck_Chris/Great_Giana_Sisters_T005.sid_MOS6581R4.mp3 R4]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/049/MP3/MUSICIANS/H/Huelsbeck_Chris/Great_Giana_Sisters_T005.sid_CSG8580R5.mp3 R5]
 +
|-
 +
| Filter clicks
 +
| [[Menu - Kangarudy#Kangarudy (C64)|Menu]]
 +
| [[Kangarudy (C64)]]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/067/MP3/GAMES/G-L/Kangarudy_T003.sid_MOS6581R3.mp3 R3]
 +
| [http://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/067/MP3/GAMES/G-L/Kangarudy_T003.sid_CSG8580R5.mp3 R5]
 +
|}
 +
 
 +
====6581 filter====
 +
Listen to the bass of [[High Score - Wizball (C64)]]:
 +
{| class="wikitable"
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/063/MP3/MUSICIANS/G/Galway_Martin/Wizball_T007.sid_MOS6581R3.mp3 R3]
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/063/MP3/MUSICIANS/G/Galway_Martin/Wizball_T007.sid_MOS6581R2.mp3 R2]
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/063/MP3/MUSICIANS/G/Galway_Martin/Wizball_T007.sid_MOS6581R4.mp3 R4]
 +
|}
 +
Do you hear the bass go deeper and deeper with every C64? Now this may be matter of taste and no big deal, but listen to [[Insects In Space]] by the same composer and skip to the melody at 1:06:
 +
{| class="wikitable"
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/049/MP3/MUSICIANS/G/Galway_Martin/Insects_in_Space_T001.sid_MOS6581R4.mp3 R4]
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/049/MP3/MUSICIANS/G/Galway_Martin/Insects_in_Space_T001.sid_MOS6581R3.mp3 R3]
 +
|}
 +
Do you hear how in the first recording, the melody has a wah-wah sound, and in the second, it almost hasn't? [[Martin Galway]] must have put some effort in the wah-wah and wanted it to be heard. It could also mean that Stone Oakvalley's R4 is closest to Galway's C128D.
 +
 
 +
Sometimes, the melody itself vanishes or sticks out unbearably:
 +
{| class="wikitable"
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/070/MP3/MUSICIANS/D/Dunn_David/Highnoon_T002.sid_MOS6581R2.mp3 R2]
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/070/MP3/MUSICIANS/D/Dunn_David/Highnoon_T002.sid_MOS6581R4.mp3 R4]
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/070/MP3/MUSICIANS/D/Dunn_David/Highnoon_T002.sid_MOS6581R3.mp3 R3]
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/070/MP3/MUSICIANS/D/Dunn_David/Highnoon_T002.sid_CSG8580R5.mp3 R5]
 +
|}
 +
 
 +
Though not as unbearable as one of the following at 0:20, 0:44 and 1:15:
 +
{| class="wikitable"
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/049/MP3/MUSICIANS/C/Cooksey_Mark/Overlander_T002.sid_MOS6581R3.mp3 R3]
 +
| [https://www.6581-8580.com/socse/dl.php?d=soasc/hvsc/049/MP3/MUSICIANS/C/Cooksey_Mark/Overlander_T002.sid_MOS6581R4.mp3 R4]
 +
|}
 +
 
 +
==Devices==
 +
{| class="wikitable" |
 +
! Release
 +
! Device
 +
! Chip
 +
|-
 +
| 1982-08-??
 +
| [[Commodore 64]]
 +
| 6581
 +
|-
 +
| 1985-01-??
 +
| [[Commodore 128]]
 +
| 6581
 +
|-
 +
| 1985-??-??
 +
| [[Commodore 128|Commodore 128D]]
 +
| 6581
 +
|-
 +
| 1986-??-??
 +
| [[Commodore 64|Commodore 64C]]
 +
| 8580
 +
|-
 +
| 1986-??-??
 +
| [[Commodore 128|Commodore 128DCR]]
 +
| 8580
 +
|-
 +
| 1989-04-??
 +
| [[SSI 2001]]
 +
| 6581
 +
|-
 +
| Unreleased
 +
| [[Commodore 65]]
 +
| 2x 8580
 +
|}
 +
 
 +
Sometime in 1982 or 1983, [[David Thiel]] bought 6581s from [[Commodore]] and had two wired on an [[arcade]] sound board. While he was testing, [[Gottlieb]]'s buyer told him that Commodore preferred all 6581s for themselves.
  
 
==Emulation Status==
 
==Emulation Status==
The most popular and accurate SID emulator is reSID (in C++ and under GPL) and used in most C64 emulators, SID players and cross-platform editors. Many of them offer to configure the clock, the SID model and the filter (called bias, curve, distortion or strength).
+
To this day, the analog parts of the 6581 model are not fully researched. For example, [[Title - Bad Cat#Bad Cat (C64)|Title - Bad Cat]] has unrealistic volume differences, and [[In the Hall of the Mountain King#The Crystals of Carus (C64)|In the Hall of the Mountain King - The Crystals of Carus]] is plain unrecognizable.
 +
 
 +
The most popular and accurate SID emulator is reSID (in C++ and under GPL) and used in most C64 emulators, SID players and cross-platform editors. Many of them allow to choose the clock frequency, model and filter (called bias, curve, strength or distortion). reSID is still being developed and found up-to-date in the VICE emulator.
  
 
==Links==
 
==Links==
 
* [http://archive.6502.org/datasheets/mos_6581_sid.pdf archive.6502.org/datasheets/mos_6581_sid.pdf] - Datasheet by Commodore from October 1982 (caution: contains incorrect information).
 
* [http://archive.6502.org/datasheets/mos_6581_sid.pdf archive.6502.org/datasheets/mos_6581_sid.pdf] - Datasheet by Commodore from October 1982 (caution: contains incorrect information).
 
* [https://en.wikipedia.org/wiki/MOS_Technology_6581 en.wikipedia.org/wiki/MOS_Technology_6581] - Wikipedia.
 
* [https://en.wikipedia.org/wiki/MOS_Technology_6581 en.wikipedia.org/wiki/MOS_Technology_6581] - Wikipedia.
* [http://sidmusic.org/sid/yannes.html sidmusic.org/sid/yannes.html] - Interview with creator Bob Yannes from August 1996.
+
* [http://sidmusic.org/sid/yannes.html sidmusic.org/sid/yannes.html] - Interview with Yannes from August 1996.

Revision as of 19:06, 3 February 2021

Sound Interface Device
8580R5 4091 - On Board.jpg
Developer: Commodore
Released: 1982-08-??
Type: Chip
Channels:

1.) Triangle Wave, Sawtooth Wave, Pulse Wave, Combined Wave or White Noise
2.) Triangle Wave, Sawtooth Wave, Pulse Wave, Combined Wave or White Noise
3.) Triangle Wave, Sawtooth Wave, Pulse Wave, Combined Wave or White Noise
4.) PCM

The Sound Interface Device (SID) is an analog synthesizer chip designed by Robert "Bob" Yannes as part of the Commodore 64 computer. It came in two models, 6581 and 8580.

In the 1970s, Yannes was influenced by the synthesizer solo at the end of Lucky Man by Emerson, Lake and Palmer and had all albums by Kraftwerk and Mike Oldfield. In 1981, aged 24, he was tasked with designing a sound chip, with a given size, in only 4 or 5 months. Yannes thought that the audio designers of the TIA, SN76489, AY-3-8914 and POKEY chips knew nothing about music. He wanted to design a professional synthesizer and fulfilled 70% of his own wish list. Unfortunately for musicians, the schedule left serious bugs and inconsistencies.

Besides sound, SID also tracks movements of connected mice or paddles and was often used as a random number generator, so if you remove the sound chip from a Commodore computer, some games may not work properly.

Channels

On each of 3 voices, you can choose:

  • Pitch up to 3848 Hz (A♯7) in 0.06 steps. This precision, especially in higher pitches, was new at the time.
  • ADSR. Due to aforementioned bugs, some notes may be delayed slightly, but audibly for musicians. The volume cannot be directly set, which Charles Callet criticized.
  • Waveform: triangle, sawtooth, pulse, noise, or combinations of the first three (with differences per model). The combined triangle and pulse resembles a guitar or slap bass.
    • Duty cycle of each pulse-based wave in 0.0244140625% steps.
    • Whether to use ring modulation on triangle-based waves.
    • Whether to use Hard Sync.
  • Whether to use the single filter.

Percussion was initially made using one noise, but from 1985 to 1987, Rob Hubbard and We M.U.S.I.C. pioneered rapidly switching waveform for more thumping percussion. However, it was somewhat lacking compared to the "deep" percussion of POKEY or AY chips, and some C64 composers like Adam Gilmore have expressed their concerns about it.

One single low-pass, band-pass, high-pass or band-reject filter can be applied to any combination of voices. A resonance from 0 to 15 and a cutoff frequency from 0 to 2047 can be chosen. Unfortunately, these values are not in any standard like Hz; worse even, they vary with every SID chip and even every computer it is socketed on. As a result, gamers often heard sections muffled or louder than intended. Most composers, including Rob Hubbard, Martin Galway, Chris Hülsbeck, Jeroen Tel and Yannes expressed their concern in interviews, and some, like Ben Daglish, Fred Gray and Chris Grigg, used the filter very sparingly or purposely avoided it. A very few games allow the gamer to alter the games' filter settings.

Both SID models can play samples in different ways, unforgettably the speech in Impossible Mission (C64). However, samples are always very CPU-intensive, around 6000 Hz and usually limited to title screens.

The current output of voice 3 can be read back: Noise was often used as random number generator, and the ADSR output was sometimes written back to modulatable registers, usually the cutoff frequency.

Versions

6581

The slap bass sounds thin, and other combined waves very quiet.

Changing SID's master volume and toggling the filter produce a click; the greater the change, the louder. A very few people worked around it by changing the volume gradually rather than at once. When they wanted to turn the filter off, they actually left it on and instead set the cutoff frequency to a bound where it made the least difference.

On the upside, clicks allow to play unsigned 4-bit PCM samples on a 4th voice. In the late 1980s, it was very popular to play digi drums over 3 SID voices.

8580

In 1986, when Yannes had long left, the only major revision of SID appeared. It started prevailing in the early 1990s.

The slap bass sounds fuller and other combined waves much louder.

The filter is consistent, but the lowest possible cutoff frequency is mute, hence some songs arranged for 6581 sound choppy on 8580. In turn, 8580 songs buzz and click annoyingly on 6581.

Clicks, and therewith the 4th voice, are quiet or even mute. This can be fixed by soldering a resistor, but by 1997, methods to reliably play samples replacing one of the 3 SID voices were becoming more popular.

Examples

This section demonstrates the above differences using recordings from up to 4 real C64s (labelled R2, R3, R4 and R5) by Stone Oakvalley's Authentic SID Collection (SOASC=):

Feature Song Game 6581 recording 8580 recording
4th voice Theme Arkanoid (C64) R2 R5
Slap bass Underground Labyrinth: The Computer Game (C64) R2 R5
Other combined waves Theme Impossible Mission II (C64) R2 R5
Filter minimum Main Menu The Great Giana Sisters (C64) R4 R5
Filter clicks Menu Kangarudy (C64) R3 R5

6581 filter

Listen to the bass of High Score - Wizball (C64):

R3 R2 R4

Do you hear the bass go deeper and deeper with every C64? Now this may be matter of taste and no big deal, but listen to Insects In Space by the same composer and skip to the melody at 1:06:

R4 R3

Do you hear how in the first recording, the melody has a wah-wah sound, and in the second, it almost hasn't? Martin Galway must have put some effort in the wah-wah and wanted it to be heard. It could also mean that Stone Oakvalley's R4 is closest to Galway's C128D.

Sometimes, the melody itself vanishes or sticks out unbearably:

R2 R4 R3 R5

Though not as unbearable as one of the following at 0:20, 0:44 and 1:15:

R3 R4

Devices

Release Device Chip
1982-08-?? Commodore 64 6581
1985-01-?? Commodore 128 6581
1985-??-?? Commodore 128D 6581
1986-??-?? Commodore 64C 8580
1986-??-?? Commodore 128DCR 8580
1989-04-?? SSI 2001 6581
Unreleased Commodore 65 2x 8580

Sometime in 1982 or 1983, David Thiel bought 6581s from Commodore and had two wired on an arcade sound board. While he was testing, Gottlieb's buyer told him that Commodore preferred all 6581s for themselves.

Emulation Status

To this day, the analog parts of the 6581 model are not fully researched. For example, Title - Bad Cat has unrealistic volume differences, and In the Hall of the Mountain King - The Crystals of Carus is plain unrecognizable.

The most popular and accurate SID emulator is reSID (in C++ and under GPL) and used in most C64 emulators, SID players and cross-platform editors. Many of them allow to choose the clock frequency, model and filter (called bias, curve, strength or distortion). reSID is still being developed and found up-to-date in the VICE emulator.

Links