Intel VC820 - Desktop Board Motherboard Design Manual page 22

Introduction
1.4.6 AC'97
The Audio Codec'97 (AC'97) Specification defines a digital link that can be used to attach an
audio codec (AC), a modem codec (MC), an audio/modem codec (AMC), or both an AC and an
MC. The AC'97 Specification defines the interface between the system logic and the audio or
modem codec known as the AC'97 Digital Link.
The ability to add cost-effective audio and modem solutions is important as the platform migrates
away from ISA. In addition, the AC'97 audio and modem components are software configurable.
This reduces configuration errors. Intel
only replaces ISA audio and modem functionality, but also improves overall platform integration
by incorporating the AC'97 digital link. Using Intel
reduces cost and eases migration from ISA.
By using an audio codec, the AC'97 digital link allows for cost-effective, high-quality, integrated
audio on the Intel
with the use of a modem codec. Several system options exist when implementing AC'97. Intel
820 chipset's integrated digital link allows two external codecs to be connected to the ICH. The
system designer can provide audio with an audio codec
codec (Figure
audio codec and the modem codec can be integrated into a single Audio Modem Codec (AMC)
(Figure 1-4c), or separate audio and modem codecs can be connected to the ICH
Modem implementation for different countries must be considered as telephone systems may vary.
By using a split design, the audio codec can be on-board and the modem codec can be placed on a
riser. With a single integrated codec, or AMC, both audio and modem can be routed to a connector
near the rear panel where the external ports can be located.
The digital link in the ICH is AC'97 Rev. 2.1 compliant, supporting two codecs with independent
PCI functions for audio and modem. Microphone input and left and right audio channels are
supported for a high quality two-speaker audio solution. Wake on ring from suspend is also
supported with an appropriate modem codec.
1-10
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820 chipset platform. In addition, an AC'97 soft modem can be implemented
1-4b). For systems requiring both audio and a modem, there are two solutions. The
820 chipset's AC'97 (with the appropriate codecs) not
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820 chipset's integrated AC'97 digital link
(Figure 1-4a) or a modem with a modem
Intel
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(Figure 1-4d).
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820 Chipset Design Guide