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furnace/doc/7-systems/pcspkr.md
tildearrow c6a9277d51 document chip options
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PC Speaker

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

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.

be noted that this will only work on Linux as Windows does not provide any user-space APIs to address the PC speaker directly!

you may configure the output method by going 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.
    • is 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 it CAP_SYS_RAWIO to the Furnace executable: sudo setcap cap_sys_rawio=ep ./furnace.

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

effects

ha! effects...

info

this chip uses the Beeper instrument editor.

chip config

the following options are available in the Chip Manager window:

  • Clock rate: sets the rate at which the chip will run.
  • Speaker type: select which speaker to use:
    • Unfiltered: raw square wave.
    • Cone: filter it 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. only works on Linux!
  • Reset phase on frequency change: reset phase every time the frequency changes. many modern motherboards tend to do this.