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40 years of one square beep - and still going! Single channel, no volume control…

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Real Output

So far this is the only chip in Furnace which has a real hardware output option. To enable it, select File > Configure Chip… > PC Speaker > Use system beeper. Note: This will only work on Linux as Windows does not provide any user-space APIs to address the PC speaker directly!

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Output Methods

You may configure the output method in Settings > Emulation > PC Speaker strategy:
  • evdev SND_TONE: Uses input events to control the beeper
    • Requires write permission to /dev/input/by-path/platform-pcspkr-event-spkr
    • Not 100% frequency-accurate as SND_TONE demands frequencies but Furnace uses raw timer periods
  • KIOCSOUND on /dev/tty1: Sends the KIOCSOUND ioctl to control the beeper
    • May require running Furnace as root
  • /dev/port: Writes to /dev/port to control the beeper
    • Requires read/write permission to /dev/port
  • KIOCSOUND on standard output: Sends the KIOCSOUND ioctl to control the beeper
    • Requires running Furnace on a TTY
  • outb(): Uses the low-level kernel port API to control the beeper
    • Requires running Furnace as root, or granting CAP_SYS_RAWIO: sudo setcap cap_sys_rawio=ep ./furnace

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Important Warnings

Real hardware output only works on BIOS/UEFI (non-Mac) x86-based machines! Attempting this on any other device will not work, or may even brick the device (if using /dev/port or outb())! You also need the beeper to be present in your machine. Some laptops connect the beeper output to built-in speakers (or audio jack), and some don’t do this at all.

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Effects

Ha! Effects…

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ROM Export

Two ROM export options exist:

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iPod .tone alarm

With the iPod in disk mode, drag the export file into the iPod_Control/Tones directory.

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GRUB_INIT_TUNE

Use with the GRUB bootloader:
  • Add to /etc/default/grub: GRUB_INIT_TUNE="text" (replace “text” with exported content)
  • Then regenerate GRUB config
  • Export binary file: Creates a binary file instead of text. In the GRUB shell or config, use the play command followed by the exported file’s name.

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Chip Configuration

Clock rate: Sets the rate at which the chip will run Speaker type: Select which speaker to use:
  • Unfiltered: Raw square wave
  • Cone: Filter to simulate the sound of a cone speaker
  • Piezo: Simulate the tiny speaker present in most PCs from the 2000s
  • Use system beeper: Use the actual PC speaker in your machine for output (Linux only)
Reset phase on frequency change: Reset phase every time frequency changes. Many modern motherboards do this.

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