AC97 versus PCI - The Audio Functions of the Motherboards
Nine of the ten motherboards we tested came with audio functionality. Most are equipped with only a small codec chip. For those the processor has to divert some computing power to the audio part, at least in theory.
The Chaintech 7AJA and the IWill KV200-R use the PCI sound chip CMI8738. It requires its' own interrupt. Contrary to a cheap codec chip, the CMI8738 allows assigning functions to the inputs and outputs on the mentioned motherboards. For example it is possible to play DVD videos over SPDIF with 3D sound. All it takes is 'reprogramming' one audio connection (usually line-in).
Gigabyte uses a sound chip from Creative on the GA-7ZX. Similar to the CMI8738 it needs an interrupt. If you install the audio drivers you will notice that it is the same chip that sits on the Soundblaster PCI128 sound card. To enable 3D sound you can connect four speakers to the motherboard.
In this case line-in becomes the second lineout if the function is activated. Despite the more popular brand name the Creative chip offers the same performance as the CMI8738. We compared the two PCI sound chips with the codec chips, and we expected that the PCI chips do not strain the CPUs as much. In the test we had to find out that the differences between PCI sound and audio codec are minimal. The codec chips are definitely sufficient for regular stereo sound (without 3D effects). The PCI chips CMI8738 and Creative CT5880 offer more features however.