Q. AC'97 Front Panel Audio Does Not Work with Onboard HD Audio

A. The onboard front panel audio connector provides microphone in and line out signals for the front panel. Many chassis manufacturers offer chassis with front panel audio ports and cabling. Those front panel solutions may support either AC'97 audio or High Definition (HD) audio.
The onboard audio headers on Intel® Desktop Boards with the Intel® 945 chipset and later support HD audio.

Compatibility:
HD front panel audio solutions should be plugged into HD onboard headers.
AC'97 front panel audio solutions should be plugged into AC'97 onboard headers.
Some AC'97 front panel audio solutions (but not all) may work with HD onboard headers.
If you want connect an AC'97 front panel audio system to HD onboard headers, try these steps:
Connect Mic_IN (MIC) to MIC2_L.
Connect Audio_R (RIN) to OUT2_R
Connect Audio_L (LIN) to OUT2_L.
MIC_RET and OUT_RET are for HD audio only; you don't need to connect them for AC'97 audio.

Note: Intel does not validate AC'97 front panel audio solutions with boards using HD audio. If the steps above do not work, you will need to use an HD front panel audio solution for full compatibility with Intel Desktop Boards using Intel® 945 chipsets and later.

Additional resources:
Front Panel Audio Header Pinouts http://support.intel.com/support/m [...] 015851.htm
Intel Front Panel I/O Connectivity Design Guide - PDF http://www.formfactors.org/develop [...] 04-005.pdf BEGIN Page 19