The new PC motherboard form factor BTX (Balanced Technology Extended) has been developed to accommodate the latest processors and the problems arising from their ever-increasing clock rates.
It sounds as though the BTX standard takes system design tips from Apple's G5 when it comes to thermal and acoustic performance.
The BTX form factor uses an inline airflow layout to cool the hottest computer components with fewer fans. It does this by simply positioning the processor, chipset and graphics processors in the same vicinty on the board to one another allowing easier cooling, less fans and less noise. That's the theory anyway.
When Apple's G5 was introduced PC owners chuckled to themselves when they heard it contained 9 fans, but because of the internal layout spliting the chassis into thermal zones it enabled these fans to work at very low revs, keeping noise to a minimum and the system cool.
Hopefully with these new boards which also embrace the new PCI Express and Serial ATA technologies we will once again be able to have powerful PC's that don't sound like they are about to take off.
BTX form factor details