A Joint SW/HW Approach for Reducing Register File Vulnerability

The Register File (RF) is a particularly vulnerable component within processor core and at the same time a hotspot with high power density. To reduce RF vulnerability, conventional HW-only approaches such as Error Correction Codes (ECCs) or modular redundancies are not suitable due to their significant power overhead. Conversely, SW-only approaches either have limited improvement on RF reliability or require considerable performance overhead. As a result, new approaches are needed that reduce RF vulnerability with minimal power and performance overhead. This article introduces Application-guided Reliability-enhanced Register file Architecture (ARRA), a novel approach to reduce RF vulnerability of embedded processors. Taking advantage of uneven register utilization, ARRA mirrors, guided by a SW instrumentation, frequently used active registers into passive registers. ARRA is particularly suitable for control applications, as they have a high reliability demand with fairly low (uneven) RF utilization. ARRA is a cross-layer joint HW/SW approach based on an ARRA-extended RF microarchitecture, an ISA extension, as well as static binary analysis and instrumentation. We evaluate ARRA benefits using an ARRA-enhanced Blackfin processor executing a set of DSPBench and MiBench benchmarks. We quantify the benefits using RF Vulnerability Factor (RFVF) and Mean Work To Failure (MWTF). ARRA significantly reduces RFVF from 35% to 6.9% in cost of 0.5% performance lost for control applications. With ARRA’s register mirroring, it can also correct Multiple Bit Upsets (MBUs) errors, achieving an 8x increase in MWTF. Compared to a partially ECC-protected RF approach, ARRA demonstrates higher efficiency by achieving comparable vulnerability reduction at much lower power consumption.