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40 AC ’97 Programmer’s Reference Manual
Table 20. Multiple Codec Audio Channel Distribution
Split Audio Codec Configuration
Primary Secondary Tertiary Total Channels
L/R - - 2
L/R S-L/R - 4
L/R S-L/R;
C/LFE
- 6
L/R S-L/R C/LFE 6
Legend:
L/R: Left Stereo Channel (Slot 3); Right Stereo Channel (Slot 4)
S-L/R: Surround Left Channel (Slot 7); Surround Right Channel (Slot 8)
C/LFE: Center Channel (Slot 6); Low Frequency Enhancement “subwoofer” (Slot 9)
(-): Not Applicable for this configuration could be used for simultaneous S/PIDF output
4.2 Enabling Intel
®
ICH5 AC ’97 Controller Audio
Channels
The ICH5 indicates how many channels supports in its Global Status Register. The ICH5 AC ’97
controller defaults to PCM stereo after system reset or suspend-resume from S3, S4 or S5. Audio
drivers can determine the total number of channels and re-configure the controller to support either
4 or 6 channel audio for PCM Out only. PCM In and PCM2 In are not configurable and are always
set for 2 -channel input. PCM MIC In and PCM2 MIC In are also not configurable and are always
single channel (monaural.) The total numbers of audio channels supported are indicated at:
MBBAR + 30h: Global Status Registers.
Table 21. CM 4/6 –PCM Channels Capability Bits
Bit Description
21:20 PCM 4/6 Capability:: These read-only bits indicate the capability to support more than 2 channels
for the PCM OUT. These bits will both be 1 to indicate that the Intel
®
ICH5 supports both 4 and 6-
channel PCM output.
The ICH5 AC ’97 controller also provides support for an independent DMA channel to provide
simultaneous S/PDIF output stream. This allows for concurrent PCM surround out with AC3
compress over S/PDIF interface. ICH5 AC ’97 controller follows slot assignments described in
Section 5.4.2.1 and Table 13 of the AC ’97 Component Specification, Revision 2.3.
System software enables the number of channels it intends to provide to the codec at:
MBBAR + 2Ch: Global Control Registers.