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Aging Mitigation for Arithmetic and Logic Unit of a Processor

Sharifi, Ferdous | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51160 (19)
  4. University: Sharif University of Technology
  5. Department: Computer Engineering
  6. Advisor(s): Hesabi, Shahin
  7. Abstract:
  8. Shrinking the dimensions of transistors in recent fabrication technologies has led to an increase in the aging rate of chips, as the most important challenge in reliability of new processors. Bias Temperature Instability (BTI) and Hot Carrier Injection (HCI) are amongst the most important adverse effect of transistor shrinkage. These two effects decrease the switching speed of transistors by increasing its threshold voltage over time. Threshold voltage shift causes timing violation in combinational parts of circuit and decreases the robustness of sequential parts against soft errors. Between different units of a processor, Arithmetic and Logic Unit (ALU) is one of the most susceptible units of the processor due to its higher switching rate and temperature. To mitigate the negative effects of aging, a guard band of 20% is considered for operational frequency and voltage to ensure safe operation over the life of the chip, which has power, area, and performance overheads. By controlling the effective factors on the aging phenomenon, some aging mitigation techniques have been proposed in the literature. However, guard banding is still the most common technique to mitigate aging because of its relative effectiveness and lower cost compared to most of the previous works. This work proposes a task scheduling technique to balance the workload on each core on a multi-core processor to maximize the lifetime of the entire system. The proposed aging mitigation technique decreases the critical path delay extension due to aging by 35% with negligible performance overhead of less than 7%. The experimental setup and tool chain to analyze the proposed techniques include gem5, HotSpot, HSPICE, Matlab, and Design Compiler
  9. Keywords:
  10. Aging ; Bias Temperature Instability (BTI) ; Scheduling ; Reliability ; Arithmetic-Logic Unit (ALU)

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