Intel FSB800 (PC3200) - Manual (Page 74)

Drivers Installation
Page 5-4
3. Volume Control:
C-Media driver provides the digital volume control for all 6 channels in 3D
Audio Configuration. You can regulate each volume to the speaker for current
playing digital sound sources. It’s not effective for analog input sources.
2. S/PDIF:
C-Media driver supports digital S/PDIF output (Sony/Philips Digital InterFace,
developed by SONY/PHILIPS to provide a low-distortion digital data transfer
between audio devices). There may be an optical or coaxial connector for S/PDIF
on your system. When you select S/PDIF tab, you will see the setting page as the
figure below.