Randomized Pulse-Modulating Instruction-Issue Control Circuit for a Current and Temperature Limiting System in a 7nm Hexagon™ Compute DSP

Abstract

A randomized pulse-modulation (RPM) circuit controls the instruction-issue rate in a Qualcomm® Hexagon™ compute DSP (CDSP) for adapting performance to limit current and temperature below target thresholds. The current and temperature limiting system contains on-die current and temperature sensors, a limits evaluation (LE) circuit, and the RPM instruction-issue control circuit. When current or temperature exceeds a target threshold, the RPM instruction-issue control circuit adjusts performance in ~5 CDSP clock cycles after accounting for the clock-domain-crossing synchronization overhead to satisfy the 1µs latency requirement for the entire limiting system. Silicon measurements from a 7nm Hexagon™ CDSP demonstrate that the RPM instruction-issue control circuit enables a 0.4% performance resolution across a wide range of operation from 100% to 0.4% while avoiding thread starvation during multi-threaded execution to maintain quality of service.