Energy Reduction through Differential Reliability and Lightweight Checking

As technology feature sizes shrink, aggressive voltage scaling is required to contain power density. However, this also increases the rate of transient upsets-potentially preventing us from scaling down voltage and possibly even requiring voltage increases to maintain reliability. Duplication with checking and triple-modular redundancy are traditional approaches to combat transient errors, but spending 2-3× the energy for redundant computation can diminish or reverse the benefits of voltage scaling. As an alternative, we explore the opportunity to use checking computations that are cheaper than the base computation they are guarding. We identify and evaluate the effectiveness of lightweight checks in a broad set of common FPGA tasks in scientific computing and signal and image processing. We find that the lightweight checks cost less than 14% of the base computation. Using an exponential model for the relationship between voltage and transient upset rate, we are able to show over 80% net energy reduction by aggressive voltage scaling without compromising reliability compared to operation at the nominal voltage.