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 HWsSW 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 35p to 6.9p in cost of 0.5p 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.
['Hamed Tabkhi', 'Gunar Schirner']
A Joint SW/HW Approach for Reducing Register File Vulnerability