An Instruction-Driven Adaptive Clock Management Through Dynamic Phase Scaling and Compiler Assistance for a Low Power Microprocessor

This paper presents an instruction-driven adaptive clock management scheme using a dynamic phase scaling (DPS) operation and compiler-assisted cross-layer design methodology for a low power microprocessor. The intrinsic instruction-level timing variation is explored on an ARMv7 ISA pipeline architecture. The clock period can be dynamically adjusted by a multi-phase all-digital PLL, with the timing encoded into the instruction set at the compiler level. Special compiler optimization schemes are also presented through reorganizing the runtime instruction sequences to better exploit the dynamic timing slack. In addition, an instruction timing calibration scheme is proposed to characterize the instruction delay under process, voltage, and temperature (PVT) variations, which can be integrated with the conventional dynamic voltage and frequency scaling (DVFS). The implementation of 55-nm CMOS process shows a 20% performance improvement from the proposed instruction-driven adaptive clock management. The performance improvement can be equivalently converted up to 32% energy saving benefit.