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16 AC ’97 Programmer’s Reference Manual
2.1.5 Second Independent Input DMA Engines
The ICH5 continues to provide two sets of input DMA engines that allow for the secondary or
tertiary codecs to provide recording PCM data streams on the primary codec while simultaneously
providing recording capabilities from the secondary or tertiary codec. A typical application is to
provide independent input stream in a mobile docking configuration where an audio codec is
located in the base system (notebook unit) and the secondary or tertiary codec is located in a
docking unit for desktop replacement. The DMA engines provide the infrastructure for s/w to
select the input stream from either source for stereo or microphone recording. Also the capability
of simultaneous input streams opens the possibilities for more futuristic applications where a
multiple microphone array can be created using two codecs. Refer to Section 3.2 for more
information on how to program the DMA engines.
2.1.6 PCI Local Bus Specification, Revision 2.3 Power
Management
The ICH5 provides PCI Local Bus Specification, Revision 2.3-compliant power management
registers that allows for better OS power management support with reduced overhead to the BIOS
programmers using ACPI control methodologies.
2.2 General Requirements
It is assumed that the reader has a working knowledge of AC ’97 architecture and the ICH5 AC’97
controller implementation. Also, the reader should have an understanding of audio driver
development for the target operating systems.
This document outlines the software specification for the AC ’97 digital controller, and also
includes details necessary for development of an audio device driver.