6158c37aaf
add Supervision and OPL4 to 7-systems and 4-instrument improve wording in C64 and SNES description
109 lines
5.1 KiB
Markdown
109 lines
5.1 KiB
Markdown
# Commodore 64
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a home computer with a synthesizer-grade sound chip of which people took decades to master. three oscillators with four selectable waveforms, ring modulation, oscillator sync, multi-mode filter and ADSR envelope.
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very popular in Europe and mostly due to the demoscene, which stretched the machine's limbs to no end.
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two versions of aforementioned chip exist: 6581 (original chip) and 8580 (improved version with working waveform mixing and somewhat more consistent filter curves).
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the 6581 has a hardware quirk which produces a DC output with its intensity being regulated by the global volume register. this register can be abused to produce a crude, virtual fourth 4-bit PCM channel.
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Furnace supports this with the "Commodore 64 (SID 6581) with software PCM" system. the later 8580 chip fixed this problem, making such PCM nearly inaudible; while other PCM playback methods have been invented, Furnace does not support them at the moment.
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## effects
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- `10xx`: **change wave.** the following values are accepted:
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- `00`: nothing
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- `01`: triangle
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- `02`: saw
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- `03`: triangle and saw
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- `04`: pulse
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- `05`: pulse and triangle
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- `06`: pulse and saw
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- `07`: pulse and triangle and saw
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- `08`: noise
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- `11xx`: **set coarse cutoff.** `xx` may be a value between `00` and `64`.
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- _this effect only exists for compatibility reasons, and its use is discouraged._
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- use effect `4xxx` instead.
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- `12xx`: **set coarse duty cycle.** `xx` may be a value between `00` and `64`.
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- _this effect only exists for compatibility reasons, and its use is discouraged._
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- use effect `3xxx` instead.
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- `13xx`: **set resonance.** `xx` may be a value between `00` and `0F`.
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- `14xx`: **set filter mode.** the following values are accepted:
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- `00`: filter off
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- `01`: low pass
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- `02`: band pass
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- `03`: low+band pass
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- `04`: high pass
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- `05`: band reject/stop/notch
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- `06`: high+band pass
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- `07`: all pass
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- `15xx`: **set envelope reset time.**
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- this is the amount of ticks the channel turns off before a note occurs in order to reset the envelope safely.
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- if `xx` is 0 or higher than the song speed, the envelope will not reset.
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- `1Axx`: **disable envelope reset for this channel.**
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- `1Bxy`: **reset cutoff**:
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- if `x` is not 0: on new note
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- if `y` is not 0: now
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- this effect is not necessary if the instrument's cutoff macro is absolute.
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- `1Cxy`: **reset duty cycle**:
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- if `x` is not 0: on new note
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- if `y` is not 0: now
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- this effect is not necessary if the instrument's duty macro is absolute.
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- `1Exy`: **change additional parameters.**
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- _this effect only exists for compatibility reasons, and its use is discouraged._
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- `x` may be one of the following:
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- `0`: attack (`y` from `0` to `F`)
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- `1`: decay (`y` from `0` to `F`)
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- `2`: sustain (`y` from `0` to `F`)
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- `3`: release (`y` from `0` to `F`)
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- `4`: ring modulation (`y` is `0` or `1`)
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- `5`: oscillator sync (`y` is `0` or `1`)
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- `6`: disable channel 3 (`y` is `0` or `1`)
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- `20xy`: **set attack/decay.**
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- `x` is the attack.
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- `y` is the decay.
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- `21xy`: **set sustain/release.**
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- `x` is the sustain.
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- `y` is the release.
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- `22xx`: **pulse width slide up.**
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- `xx` is speed. if it is `00`, the slide is stopped.
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- `23xx`: **pulse width slide down.**
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- `xx` is speed. if it is `00`, the slide is stopped.
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- `24xx`: **filter cutoff slide up.**
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- `xx` is speed. if it is `00`, the slide is stopped.
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- `25xx`: **filter cutoff slide down.**
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- `xx` is speed. if it is `00`, the slide is stopped.
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- `3xxx`: **set duty cycle.** `xxx` range is `000` to `FFF`.
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- `4xxx`: **set cutoff.** `xxx` range is `000` to `7FF`.
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## info
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this chip uses the [C64](../4-instrument/c64.md) instrument editor.
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## channel status
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the following icons are displayed when channel status is enabled in the pattern view:
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- channel is silent:
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-  it's not
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-  gate bit disabled
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-  gate bit disabled and test bit enabled
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-  test bit enabled
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-  ch3off enabled in filter mode
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## chip config
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the following options are available in the Chip Manager window:
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- **Clock rate**: sets the rate at which the chip will run.
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- **Global parameter priority**: change the priority of macros which control global parameters, such as volume and filter.
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- Left to right: process channels from 1 to 3. the last one to run macros will take effect.
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- Last used channel: process channels from oldest to newest (since last note). the one which had the latest note on will take a effect.
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- **Hard reset envelope**: configure the envelope parameters used during the short reset before a note.
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- **Envelope reset time**: set how long will the pre-note reset last, in ticks.
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- 0 disables reset, which prevents notes from triggering.
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- 1 is short, but may exhibit SID envelope bugs.
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- 2 is a good value.
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the other options are for compatibility with old Furnace and DefleMask, so they won't be documented here.
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