(Audio Codec'97) A specification for audio and modem circuits on a PC motherboard. Introduced in 1996 by Intel, AC'97 provides six channels (5.1) of 20-bit, 48 kHz audio. It supports one audio stream per system and a two-element array microphone.AC LinkAC'97 comprises a controller connected to analog/digital codecs by a 5-wire TDM interface called "AC Link." The two subsystems separate the digital controller, which is built into the PC chipset, from the analog circuits, which can be in a chip on the motherboard, in an interchangeable riser card or cabled close to the I/O connectors. For international certification (homologation), modem codecs are often placed on riser cards. See HD Audio and riser card.