furnace/doc/7-systems/pcspkr.md

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...