A 90-nm Variable Frequency Clock System for a Power-Managed Itanium Architecture Processor

An Itanium Architecture microprocessor in 90-nm CMOS with 1.7B transistors implements a dynamically-variable-frequency clock system. Variable frequency clocks support a power management scheme which maximizes processor performance within a configured power envelope. Core supply voltage and clock frequency are modulated dynamically in order to remain within the power envelope. The Foxton controller and dynamically-variable clock system reside on die while the variable voltage regulator and power measurement resistors reside off chip. In addition, high-bandwidth frequency adjustment allows the clock period to adapt during on-die supply transients, allowing higher frequency processor operation during transients than possible with a single-frequency clock system.