"Though Intel has been promoting the spec for a while, the company only recently rolled out its first retail BTX boards. It expects to offer three variants (all 10.5 inches long): standard BTX, with seven or fewer PCI Express slots (up to 12.8 inches wide each); MicroBTX (pictured, up to 10.3 inches wide), with four or fewer slots; and PicoBTX, with one slot (up to 7.9 inches wide).
Intel's first two boards are both MicroBTX models; the chip maker has begun shipping CPUs with the Type I BTX Thermal Module (which replaces the traditional heat sink and fan combination; see picture), too. Companies such as AOpen have begun to offer BTX-based chassis, since you can't place a BTX motherboard and Thermal Module in an ATX case. Expect standard BTX and PicoBTX boards to emerge sometime this year.
Intel insists the new spec will benefit the PC industry as a whole. Certainly most people want a quieter PC. Microprocessor Report editor-in-chief Kevin Krewell notes, though, that one of Intel's motives for creating BTX was to deal with the Pentium 4's heat problems. "The Pentium 4 is hotter than the Athlon 64," he says. "Intel has to contend with that chip's greater power requirements."