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

Abstract

An all-digital dynamically adaptive clock distribution mitigates the impact of high-frequency supply voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CC</sub> ) 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 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CC</sub> droop. The tunable-length delay prevents critical-path timing-margin degradation for multiple cycles after the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CC</sub> droop occurs, thus allowing a sufficient response time for dynamic adaptation. An on-die dynamic variation monitor detects the onset of the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CC</sub> 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% V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CC</sub> droop.