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# Topological Affinities of Nets on a Module

IP.com Disclosure Number: IPCOM000046413D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 41K

IBM

## Related People

Ditlow, GS: AUTHOR

## Abstract

Solutions to nets on a module are ordered efficiently by computing the minimum spanning tree and subtracting it from each allowable solution of the net to obtain the respective differences. The solutions are ordered in accordance with the absolute value of the respective differences.

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Topological Affinities of Nets on a Module

Solutions to nets on a module are ordered efficiently by computing the minimum spanning tree and subtracting it from each allowable solution of the net to obtain the respective differences. The solutions are ordered in accordance with the absolute value of the respective differences.

The interconnections between chips on a module are "trees". These trees assume a variety of topologies. They can range from chains to trees which fan out only from the driver to each receiver. Some typical configurations for a 5-pin net are:

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Assume that the above configurations are allowable solutions for a given technology. Notice that there are some 5-pin trees which are not included. For example,

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This solution may not be allowable for some electrical reason which was verified through circuit analysis.

The following is an efficient procedure for selecting which trees to process first. First, compute the minimum spanning tree for a net.

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Create an identifying vector for this tree by traversing it in a depth- first search order (keeping track of the fan out at each vertex).

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Each allowable tree also has an identifying vector.

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If the minimum spanning tree (MST) is in the solution of trees, then the task is finished. Otherwise, one must process the trees in some order. The order resulting from the following procedure is preferred. (1) Subtract the MST vector from eac...