For example, low-cost PCs can benefit from a barebones controller chip with two nonsynchronous buck controllers, each achieving a typical efficiency of 85 per cent. Devices like these reduce a motherboard's space requirements and cost, no small benefit given the motherboard's crowded circuitry and cut throat pricing. To appreciate the power demands imposed by today's PC microprocessors, consider some typical requirements. A 300MHz Intel Pentium processor with MMX capability has a typical requirement of 2.8V at 5.7A for its core. Pentium processor clones offer no relief.
Future trends suggest still higher current consumption and more severe load transients.
Their efficiency is simply too low, producing excessive heat and requiring costly power dissipation hardware. In particular, synchronous and nonsynchronous buck controllers, with their simple topology and high efficiency, have become a leading choice for powering a processor's core. In a synchronous topology for example, switch Q1 turns on at the start of each switching cycle. When that happens, a voltage equal to the supply voltage less the output voltage appears across the inductor. At this point, the output voltage appears across the inductor.