Timing ECO Optimization Via Bezier Curve Smoothing and Fixability Identification
DOI: 10.1109/ICCAD.2011.6105412 Conference: 2011 IEEE/ACM International Conference on Computer-Aided Design (ICCAD), San Jose, California, USA, November 7-10, 2011
Due to the rapidly increasing design complexity in modern IC design, more and more timing failures are detected at late stages. Without deferring time-to-market, metal-only ECO is an economical technique to correct these late-found failures. Typically, a design undergoes many ECO runs in design houses; the usage of spare cells is of significant importance. Hence, in this paper, we aim at timing ECO using the least number of spare cells. We observe that a path with good timing is desired to be geometrically smooth. Different from negative slack and gate delay used in most of prior work, we propose a new metric of timing criticality-fixability-considering the smoothness of critical paths. To measure the smoothness of a path, we use Bézier curve as the golden path. Furthermore, in order to concurrently fix timing violations, we derive the dominance property to divide violated paths into independent segments. Based on Bézier curve smoothing, fixability identification, and the dominance property, we develop an efficient algorithm to fix violations. Compared with the state-of-the-art works, experimental results show that our algorithm not only effectively resolves all timing violations with few spare cells but also achieves 22.8X and 42.6X speedups.
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ABSTRACT: Due to the rapidly increasing design complexity in modern IC designs, metal-only engineering change order (ECO) becomes inevitable to achieve design closure with a low respin cost. Traditionally, preplaced redundant standard cells are regarded as spare cells. However, these cells are limited by predefined functionalities and locations, and they always consume leakage power despite their inputs are tied off. To overcome the inflexibility and power overhead, a new type of spare cells, metal-configurable gate-array spare cells, are considered. Therefore, in this paper, we address a new ECO problem: Timing ECO optimization using metal-configurable gate-array spare cells. We first study the properties for this new ECO problem, propose a new metric, aliveness, to model the capability of a spare gate array, and then develop a timing ECO optimization framework based on aliveness, routability, and timing satisfaction. Experimental results show that our approach delivers superior efficiency and effectiveness.IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems 11/2013; 32(11). DOI:10.1145/2228360.2228505 · 1.00 Impact Factor
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ABSTRACT: Metal-configurable gate-array spare cells, which have versatile functionality, are developed to overcome the inflexibility of standard spare cells used in conventional metal-only engineering change order (ECO). In this paper, we focus on functional ECO optimization using the new type of spare cells to fully exploit its strength. We observe that this functional ECO problem has the nature of dynamic logical and physical costs for selecting spare gate arrays. Unlike existing functional ECO works, which perform technology mapping based on ECO patches, we perform reverse mapping from spare gate arrays to handle these dynamic costs. We devise a spare array relation graph to record geometrical adjacency among spare gate arrays and interleave with the and-inverter network of ECO patches. To avoid redundant traversal and monitor the dynamic costs, we adopt A* search to simultaneously traverse and map between the logical ECO network and the physical spare array relation graph.
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