Optimizing Clock Skew Schedules Under Normal Process Variation

نویسندگان

  • Aaron P. Hurst
  • Robert K. Brayton
چکیده

Statistical timing techniques are used to quantify the effects of process variation on performance and yield. Applied to analysis, they have been successful in reducing the overconservatism in traditional worst-case methods; applied to optimization, they can produce circuits with better performance under process variation. In this paper, we examine the problem of variation-aware clock skew scheduling. Clock skew scheduling is formulated traditionally as a set of linear constraints on worst-case timing and thus suffers from the limitations of this timing model, resulting in performance/yield suboptimality. We present a technique for optimizing clock skew schedules based on a statistical model of timing. We describe a tractable but accurate approximation of the problem and use conjugate gradient optimization to compute a schedule that improves the yield for a target clock period. On a set of benchmarks, it can reduce the number of timing failures by three orders of magnitude compared to two alternate methods based on worst case optimization. Equivalently, this technique can be used to improve the performance under a yield constraint. The results indicate a 9.2% improvement in clock period for our set of benchmark circuits.

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تاریخ انتشار 2007