AC97

AC’97, short for Audio Codec ‘97, is a PC audio standard developed in the late 1990s by Intel and industry partners to define a common interface between a host audio controller and an audio codec. The goal was to standardize how audio data and control information are exchanged, enabling interchangeable codecs and compatible drivers across different motherboards and sound cards.

Architecture and features: In an AC’97 system, the audio codec is a separate component that provides analog inputs and outputs (such as line-in, line-out, and microphone) and performs analog-to-digital and digital-to-analog conversion. The host controller communicates with the codec over a dedicated control/data bus known as AC-Link, while audio data typically flows between the codec and controller through standardized digital interfaces. The specification also includes built-in mixer functionality, basic digital signal processing features, and support for routing and level control of multiple channels, enabling stereo and various multichannel configurations.

Impact and history: Introduced in 1997, AC’97 became the dominant PC audio standard during the late 1990s and early 2000s, appearing on numerous integrated motherboard solutions and PCI sound cards from many vendors. It facilitated plug-and-play operation and helped unify driver development for multimedia applications.

Decline and successors: In the mid-2000s, Intel introduced High Definition Audio (HD Audio, also known as Azalia), offering higher bandwidth, more channels, and expanded features. HD Audio gradually supplanted AC’97 in new systems, though many legacy machines and audio components remained AC’97-compatible for years.