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Increase in Delay Uncertainty by Performance Optimization
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 2002/12/01
Print ISSN: 0916-8508
Type of Manuscript: Special Section LETTER (Special Section on VLSI Design and CAD Algorithms)
Category: Timing Analysis
performance optimization, delay increase, statistical timing analysis, delay uncertainty, transistor sizing,
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This paper discusses a statistical effect of performance optimization to uncertainty in circuit delay. Performance optimization has an effect of balancing the delay of each path in a circuit, i.e. the delay times of long paths are shortened and the delay times of short paths are lengthened. In these path-balanced circuits, the uncertainty in circuit delay, which is caused by delay calculation error, manufacturing variability, fluctuation of operating condition, etc., becomes worse by a statistical characteristic of circuit delay. Thus, a highly-optimized circuit may not satisfy delay constraints. In this paper, we demonstrate some examples that uncertainty in circuit delay is increased by path-balancing, and we then raise a problem that performance optimization increases statistically-distributed circuit delay.