Intel 815 - Manual (Page 23)

Introduction
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Intel
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815 Chipset Platform Design Guide 23
1.3.3.7 AC’97
The Audio Codec ’97 (AC’97) specification defines a digital interface 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 chipset platform’s AC’97 (with the appropriate codecs) not only replaces ISA audio and
modem functionality, but also improves overall platform integration by incorporating the AC’97
digital link. Using the chipset’s integrated AC’97 digital link reduces cost and eases migration
from ISA.
The ICH is an AC’97-compliant controller that supports up to two codecs, with independent PCI
functions for audio and modem. The ICH communicates with the codec(s) via a digital serial link
called the AC-link. All digital audio/modem streams and command/status information are
communicated over the AC-link. Microphone input and left and right audio channels are supported
for a high-quality, two-speaker audio solution. Wake-on-ring-from-suspend also is supported with
an appropriate modem codec.
By using an audio codec, the AC’97 digital link allows for cost-effective, high-quality, integrated
audio. In addition, an AC’97 soft modem can be implemented with the use of a modem codec.
Several system options exist when implementing AC’97. The chipset platform’s integrated digital
link allows two external codecs to be connected to the ICH. The system designer can provide
audio with an audio codec or a modem with a modem codec. For systems requiring both audio and
a modem, there are two solutions: the audio codec and the modem codec can be integrated into an
AMC, or separate audio and modem codecs can be connected to the ICH.
Modem implementation for different countries must be taken into consideration, as telephone
systems may vary. By implementing a split design, the audio codec can be on board and the
modem codec can be placed on a riser. Intel is developing an AC’97 digital link connector. 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.
1.3.3.8 Low-Pin-Count (LPC) Interface
In the Intel 815 chipset platform, the Super I/O (SIO) component has migrated to the Low-Pin-
Count (LPC) interface. Migration to the LPC interface allows for lower-cost Super I/O designs.
The LPC Super I/O component requires the same feature set as traditional Super I/O components.
It should include a keyboard and mouse controller, floppy disk controller, and serial and parallel
ports. In addition to the Super I/O features, an integrated game port is recommended, because the
AC’97 interface does not provide support for a game port. In systems with ISA audio, the game
port typically existed on the audio card. The fifteen-pin game port connector provides for two
joysticks and a two-wire MPU-401 MIDI interface. Consult your preferred Super I/O vendor for a
comprehensive list of the devices offered and the features supported.
In addition, depending on system requirements, specific system I/O requirements may be
integrated into the LPC Super I/O. For example, a USB hub may be integrated to connect to the
ICH USB output and extend it to multiple USB connectors. Other SIO integration targets include a
device bay controller or an ISA-IRQ-to-serial-IRQ converter to support a PCI-to-ISA bridge.
Contact your Super I/O vendor to ensure the availability of the desired LPC Super I/O features.