furnace/doc/7-systems/game-boy.md

Game Boy

the Game Boy is one of the most successful portable game systems ever made.

it has stereo sound, two pulse channels, a wave channel and a noise channel.

effects

• 10xx: change wave.
• 11xx: set noise length.
  • 0: long
  • 1: short
• 12xx: set duty cycle.
  • 0: 12.5%
  • 1: 25%
  • 2: 50%
  • 3: 75%
• 13xy: setup sweep. pulse 1 only.
  • x is the time.
  • y is the shift.
  • set to 0 to disable it.
• 14xx: set sweep direction. 0 is up and 1 is down.

info

this chip uses the Game Boy instrument editor.

"zombie mode"

the game boy's envelope hardware has a bug that can be triggered to cause the volume to step up or down only on software command. Furnace uses the same method to trigger it as LSDJ. without this technique, changing the volume directly on a note (such as volume macros do) would cause a phase reset each time, causing significant popping sounds. unfortunately, only a few emulators emulate the "zombie mode" bug properly.

chip config

the following options are available in the Chip Manager window:

• Disable anti-click: waveform switching requires a phase reset, which may cause clicks. Furnace uses a wave-position predicting algorithm to minimize these clicks. enable this option to disable it.
• Chip revision: sets the chip model to use. most of these lack audible difference, but Game Boy Advance fixed the wave channel's inversion.
• Wave channel orientation: allows you to set how is wave data written.
  • in Game Boy:
    • Exact data: wave data is written as-is. it will appear inverted in the output.
    • Exact output: wave data is inverted so it appears correctly in the output.
  • in Game Boy Advance:
    • Normal: wave data is written as-is.
    • Inverted: guess!
• Pretty please: only for compatibility with Synchronize.dmf. do not use.

links

• Gameboy sound hardware - detailed technical information

• GameBoy Sound Table - note frequency table