Evaluating the effects of reducing voltage margins for energy-efficient operation of MPSoCs

Abstract

This letter assesses the energy efficiency gains available by aggressively reducing voltage guardbands on a commercial RISC-V Multi-Processor System-on-Chip (MPSoC). Standard voltage margins ensure reliability but severely limit energy efficiency, a critical requirement for embedded systems. By operating below manufacturer-defined guardbands, the researchers achieved up to 27% energy reduction for equivalent performance, supporting future development of error detection and correction schemes utilizing core redundancy.

Report

Key Highlights

• Energy Efficiency Gain: The study demonstrated achieving up to 27% energy reduction while maintaining equivalent performance by violating the manufacturer's defined voltage guardbands.
• Objective: The primary goal is to assess practically available margins to support the development of error detection and correction (EDAC) mechanisms that leverage multicore redundancy.
• Target Platform: The assessment was conducted on a commercial RISC-V MPSoC.
• Core Finding: Significant energy margins remain available when conservative voltage guardbands, designed to mitigate Process, Voltage, and Temperature (PVT) variability, are reduced.

Technical Details

• Architecture: Multi-Processor System-on-Chip (MPSoC).
• Subject of Evaluation: Voltage margins, also known as guardbands, which are imposed on Dynamic Voltage and Frequency Scaling (DVFS) systems.
• Error Mitigation Strategy (Proposed Future Work): The work motivates the use of the inherent redundancy of multicore architectures to develop schemes capable of mitigating errors caused by aggressive voltage margin reduction (e.g., hardware/software EDAC).
• Variability Mitigation: Guardbands traditionally account for PVT (Process, Voltage, and Temperature) variability effects to assure system correctness.
• Journal Publication: The findings were formally published in the IEEE Embedded Systems Letters (Volume 16, Issue 1, March 2024).

Implications

• Maximizing RISC-V Efficiency: Since RISC-V is heavily deployed in embedded and custom hardware domains, this research provides concrete data showing how far commercial RISC-V chips can be pushed beyond conservative vendor specifications for improved power efficiency.
• Shift in Reliability Approach: The findings suggest a move away from relying solely on static, conservative voltage margins toward dynamic, active fault tolerance schemes (like redundant execution across cores) to achieve aggressive energy savings while maintaining reliability.
• Advancement in DVFS: This evaluation paves the way for advanced DVFS techniques that dynamically reduce voltage guardbands based on real-time operational conditions, critical for next-generation low-power IoT and edge computing RISC-V devices.
• Competitive Advantage: Achieving 27% energy reduction represents a significant competitive advantage for RISC-V based solutions in power-constrained environments.