A Cross-Layer Analysis of Soft Error, Aging and Process Variation in Near Threshold Computing

Abstract

Near Threshold Computing (NTC) is a promising approach to reduce the power consumption of modern VLSI designs. However, NTC designs suffer from functional failures and performance loss. Understanding the characteristics of the functional failures and variability effects is of decisive importance in order to mitigate them, and get the most out of NTC. This paper presents a cross-layer reliability analysis in the presence of soft errors, aging and process variation effects in the near threshold voltage domain. The objective is to quantify the reliability of different SRAM designs and to find a reliability-performance optimal cache organization for an NTC microprocessor. In this work, the Soft Error Rate (SER) and Signal Noise Margin (SNM) of 6T and 8T SRAM cells and their dependencies on aging and process variation are investigated by considering device, circuit and architecture level analysis. Their experimental results reveal that in NTC, process variation and aging-induced SNM degradation is 2.5X higher than in the super threshold domain while SER is 8X higher. The use of 8T instead of 6T SRAM cells can reduce the system-level SNM and SER by 14% and 22% respectively. Besides, we observe that we can find the right balance between performance and reliability by using an appropriate cache organization at NTC which is different from the super threshold.