The recent, dramatic increase in the performance of Intel and AMD CPUs has driven an increase in the sophistication and complexity of the voltage regulators that power the CPU. The biggest challenge facing power-supply designers is keeping up with increases in power levels, tighter tolerances, and faster transient requirements, while reducing the overall cost of the power supply. This article explores a brief history of pulse-width modulation (PWM), multiphase operation and current sharing, and some of the latest technological advancements that help designers meet the challenges presented by modern high-power CPUs.