When building an HTPC, most look to achieve the HD standard at a minimal cost, so to accommodate this we are seeing more motherboard manufacturers produce boards with onboard HD video and sound. Some have HDMI capabilities, which will also carry sound, and some choose to use DVI as the way to transport the HD digital image. With straight DVI, these motherboards must have an additional sound source onboard since, at this time, DVI is incapable of transferring sound by itself. We are also seeing two formats of motherboards that are equipped with the HD qualities, Micro-ATX and ATX. Micro- ATX allows for a smaller system case which will be more compact, whereas ATX will require a normal sized case and may not fit in most entertainment centers."



Link: Overclockersclub