A 22 nm All-Digital Dynamically Adaptive Clock Distribution for Supply Voltage Droop Tolerance

An all-digital dynamically adaptive clock distribution mitigates the impact of high-frequency supply voltage $({\rm V}_{{\rm CC}})$ droops on microprocessor performance and energy efficiency. The design integrates a tunable-length delay prior to the global clock distribution to prolong the clock-data delay compensation in critical paths during a ${\rm V}_{{\rm CC}}$ droop. The tunable-length delay prevents critical-path timing-margin degradation for multiple cycles after the ${\rm V}_{{\rm CC}}$ droop occurs, thus allowing a sufficient response time for dynamic adaptation. An on-die dynamic variation monitor detects the onset of the ${\rm V}_{{\rm CC}}$ droop to proactively gate the clock at the end of the tunable-length delay to eliminate the clock edges that would otherwise degrade critical-path timing margin. In comparison to a conventional clock distribution, silicon measurements from a 22 nm test chip demonstrate simultaneous throughput gains and energy reductions of 14% and 3% at 1.0 V, 18% and 5% at 0.8 V, and 31% and 15% at 0.6 V, respectively, for a 10% ${\rm V}_{{\rm CC}}$ droop.