A Fault-Tolerant Alternative to Lockstep Triple Modular Redundancy

• Main Author: Baldwin, Andrew Lockett
• Format: Others
• Published: PDXScholar 2012
• Subjects: Aliasing; Reliability; Triple modular redundancy; Semiconductors > Materials > Testing; Fault tolerance (Engineering); Semiconductors > Defects > Research; Electrical and Computer Engineering
• Online Access: https://pdxscholar.library.pdx.edu/open_access_etds/331; https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1330&context=open_access_etds

Semiconductor manufacturing defects adversely affect yield and reliability. Manufacturers expend vast resources to reduce defects within their processes. As the minimum feature size get smaller, defects become increasingly difficult to prevent. Defects can change the behavior of a logic circuit resulting in a fault. Manufacturers and designers may improve yield, reliability, and profitability by using design techniques that make products robust even in the presence of faults. Triple modular redundancy (TMR) is a fault tolerant technique commonly used to mask faults using voting outcomes from three processing elements (PE). TMR is effective at masking errors as long as no more than a single processing element is faulty. Time distributed voting (TDV) is proposed as an active fault tolerant technique. TDV addresses the shortcomings of triple modular redundancy (TMR) in the presence of multiple faulty processing elements. A faulty PE may not be incorrect 100% of the time. When a faulty element generates correct results, a majority is formed with the healthy PE. TDV observes voting outcomes over time to make a statistical decision whether a PE is healthy or faulty. In simulation, fault coverage is extended to 98.6% of multiple faulty PE cases. As an active fault tolerant technique, TDV identifies faulty PE's so that actions may be taken to replace or disable them in the system. TDV may provide a positive impact to semiconductor manufacturers by improving yield and reliability even as fault frequency increases.