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Local power model

In DSM technologies, the switching capacitance of a wire depends on its neighbors' switching activity, which determines how the coupling capacitances between wires are charged and discharged [43]. Several interconnect energy models have been proposed to take the coupling effect into consideration [47,48,49,50]. Given the wire capacitive parameters, these models generate the unit-length switched capacitance or energy based on switching patterns on a wire and its neighbors. We use the table look-up method proposed in [48], which is shown in Fig. 6 as the local power model. Other models, such as the one proposed in [49], can be readily incorporated into the synthesis flow used in our work. According to [48] we only consider the coupling from the direct neighbors, we need to find out the unit-length switched capacitance of a wire when itself and its two neighbors undergo different switching patterns, which we called three-line switching patterns as shown in Fig. 6. There are 10 different patterns in terms of power consumption [48]. Using this method, PSPICE and capacitance data from [43], we estimated the unit-length switched capacitance of the central lines for different three-line switching patterns. These data are stored in a table, called pattern-power table, for later use. If multiple metal layers are used, wires on different layers will have different capacitive parameters. For each layer, we need to generate a different pattern-power table. Together with the length of a wire, its layer assignment and three-line switching patterns, these tables can be used to estimate power consumed by the entire wire.
next up previous
Next: Global power model Up: Data transfer wires Previous: Data transfer wires
Lin Zhong 2003-10-11