BTI-Gater: An Aging-Resilient Clock Gating Methodology

Abstract

Abstract-Negative-and Positive-Bias Temperature Instability (N/PBTI) have become one of the most important reliability issues in modern semiconductor technology. N/PBTI-induced degradation depends heavily on workload, which causes imbalanced degradation and additional clock skew for clock distribution networks with clock gating features. In this work, we first analyze the effects of N/PBTI on clock paths with different clock gating use cases. Then cross-layer solutions are proposed to reduce N/PBTI-induced clock skew. Two Integrated Clock Gating (ICG) cell circuits are proposed to alternate clock idle state between logic high and logic low for each clock gating operation. A skew mitigation methodology is also proposed to select the appropriate ICG cells based on the architecture and microarchitecture context. An example of sleep scheduling is also described as a simple software-level technique that can be used in conjunction with BTI-Gater to avoid certain pathological aging scenarios. Our experiments show that BTI-Gater can balance the gated clock branches to close to 50% signal duty ratio, while guaranteeing a glitch-free clock signal with easy-to-verify timing constraints. Results on commercial processors show that BTIGater can effectively reduce N/PBTI-induced clock skew of up to 17ps, which can be converted to up to 19.7% leakage power saving compared to pure design guardbanding.

Lifetime Reliability Enhancement of Microprocessors

“…In Lai et al [2014], a clock-gating methodology, BTI-Gater, is proposed to reduce NBTI-and PBTI-induced clock skew and imbalanced degradation, which conventional clock gating may cause. The R-D model for NBTI and PBTI degradation was calibrated using a commercial process technology.…”

Reliability Modeling and Mitigation for Embedded Memories

“…• Frequency margin: By adding a margin to the frequency, aging can be mitigated as the delay of degraded paths will still fall within the clock period. For example, Lai et al investigated in [155] the impact of aging on the clock distribution network and clock skew for various clock gating schemes. The cross-layer techniques is used to reduce the impact of aging on clock skew.…”