In order to understand BTX you have to understand the motives for change. CPUs are getting hotter, graphics cards are as well, and despite all of these increases in thermal dissipation there is an increase in demand for quieter PCs. Today's ATX cases and motherboards were not designed for the incredible levels of heat that they have to deal with, and it is with this that we begin our understanding of BTX.The BTX motherboard layout is a major reorganization that moves processors closer to the front of a case where they can be directly cooled by an air intake port. Air flowing over the processor can also help cool a BTX system's graphics card and chipset, potentially making passive heat sinks sufficient for a wider range of mainstream graphics cards.
Standard BTX boards will be as large as 12.8"x10", but microBTX and picoBTX versions will be available as small as 10.4"x10.5" and 8"x10.5", respectively. PCI Express and Serial ATA will be big for BTX, too. We should start seeing boards, cases, and power supplies supporting the new standard next year.