AC'97 (Audio Codec '97; also MC'97 for Modem Codec '97) is an audio codec standard developed by Intel Architecture Labs in 1997. The standard is used in motherboards, modems, and sound cards.

Audio components integrated into chipsets consist of two component classes: an AC'97 digital controller (DC97), which is built into the I/O Controller Hub (ICH) of the chipset, and AC'97 audio and modem codecs, which are the analog components of the architecture.

AC'97 defines a high-quality, 16- or 20-bit audio architecture with surround sound support for the PC. AC'97 supports a 96 kHz sampling rate at 20-bit stereo resolution and a 48 kHz sampling rate at 20-bit stereo resolution for multichannel recording and playback. AC97 defines a maximum of 6 channels of analog audio output.

Integrated audio is implemented with the AC'97 Codec on the motherboard, a Communications and Networking Riser (CNR) card, or an audio/modem riser (AMR) card.

In 2004, Intel released the successor Intel High Definition Audio (HD Audio) which is not backward compatible with AC'97. HD Audio has the capability to define many more than AC'97's six output channels, but in practice most motherboards provide no more than 8 channels.

Read more about AC'97:  Revisions, AC-Link, Codec Chips, Front Panel Connector

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AC'97 - Front Panel Connector
... Computer motherboards often provide a connector to bring microphone and headphone signals to the computer's front panel ... Intel provides a specification for that header the signal assignments are different for AC'97 and Intel High Definition Audio headers ...