RETROTECH/ ANALYSIS
As PC sound card adoption grew through the 1990s, fewer
games used the integrated beeper and smaller piezoelectric
speakers would become more commonplace. These were
quieter, and lacked the versatility and subtlety of a larger
dynamic speaker, making some fancier audio effects far less
distinct and often too quiet.
Many modern PCs no longer come with any kind of
speaker. But motherboards still have the header connector,
so you can still install one and listen to audio designed for an
internal beeper as it was meant to be heard.Quest for polyphony
Whichever way your PC beeper
sound is implemented, it’s
monophonic, which means it can
only produce one tone at a time.
But, as with other very limited
early computer audio standards,
that wasn’t going to preventB
efore sound cards brought us polyphonic music and
CD-quality PCM (pulse-code modulation) audio
recordings, PCs could make exactly one noise: a
square wave, output through a dynamic speaker driven by the
computer’s timer chip. Launched in 1981, IBM’s first model
5150 Personal Computer had an internal 2.25in (5.7cm)
speaker, designed to produce BIOS error codes to help
diagnose problems at boot.
It was driven by the Intel 8253 Programmable Interrupt
Timer, the same piece of hardware that handled system
timing. While Timer Channel 0 was used for system
synchronisation, Timer Channel 2 was used to send square
waves to the internal speaker, making it beep.
By the 1990s, the 8252 had been superseded by the Intel
8259 Programmable Interrupt Controller (PIC), and these
days, you’ll find a modern hardware equivalent on your
motherboard’s southbridge in the form of an Intel Advanced
Programmable Interrupt Controller (APIC) variant. All of them
retain PC internal speaker functions.
K.G. Orphanides delves into the bleeps and bloops
of the PC’s original primitive sound system
The Intel 8253 chip
drove the original
PC speaker. Credit:
Wikimedia Commons