AC'97
AC'97 (Audio Codec '97; also MC'97 for Modem Codec '97) is an audio codec standard developed by Intel Architecture Labs and various codec manufacturers in 1997. The standard was used in motherboards, modems, and sound cards.
The specification covers two types of components, and the AC-Link digital interface between them:
- an AC'97 digital controller (DC97), which is typically built into the southbridge of the chipset, and
- an AC'97 audio and/or modem codec, available from several vendors, which contains the analog components of the architecture.
AC'97 defines a high-quality, 16- or 24-bit audio architecture with 5.1 surround sound support for the PC. AC'97 supports a 96 kHz sampling rate at 24-bit stereo resolution and a 48 kHz sampling rate at 24-bit stereo resolution for multichannel recording and playback.
Integrated audio is implemented with the AC'97 Codec on the motherboard, a communications and networking riser card, or an audio/modem riser card.
The first shipping system was in the Cyrix MediaGX, in 1997. Intel started shipping the initial I/O Controller Hub support in 1999, and it wasn't until public shaming in 2000, that most PC OEMs started shipping AC'97 audio as the default.
In 2004, Intel released Intel High Definition Audio (HD Audio) which is a successor that is not backward compatible with AC'97. HD Audio has the capability to define up to 15 output channels, but in practice most motherboards provide no more than 8 channels (7.1 surround sound).