International Business Machines Corporation

Keith W Lallier

Kurt D Carpenter

Roger K Jackson

David James Hathaway

Paul H Bergeron

Keith M Carrig

Jeannie T Panner

Jerome B Hickson, Jr

Elba K Malone

Terrence W Sehr

A signal distribution tree is constructed from the leaves to the root by pairing sinks having similar locations, latency requirements and generating function requirements, then determining the minimum cost route or routes between paired sinks, establishing at least one drive point for each minimum cost path which drive point will satisfy the latency requirements for the pair of sinks it serves and then treating each resulting set of drive points as a new sink to be paired while removing the initial sinks from the list of sinks to be paired, continuing this process iteratively until a single set of drive points results and, finally, connecting the signal source to one of the drive points in the final set.

Method and apparatus for making a skew-controlled signal distribution

A method of placing circuit elements in an integrated circuit. The chip area is divided into a grid. In an initial pass, the elements are randomly placed in the grid locations, and these placements are recorded. Thereafter, the elements are sequentially replaced in each of the grid locations, and a score is calculated for the wiring interconnections to the remaining elements as they were last recorded. The placement yielding the best score is recorded for that element. This placement is repeated for each of the elements. Once all the elements have been replaced, a final score is compared with the last best score. If the recent final score is better, the placements associated with that score are saved as the best placements. Then the process of replacement is repeated until a given number of iterations fails to yield a better score.

Progressive insertion placement of elements on an integrated circuit

A wire packing method for packing wire segments in wiring bays of large-scale integrated circuit devices and integrated circuit devices produced employing such a method. Each wiring segment to be placed in a channel of a wiring bay is assigned a score in accordance with criteria developed for the particular application. The start point, end point and a segment identifier is recorded for each segment to be packed. For each channel, segments which can be considered candidates for packing in that channel are extracted from the list. For that channel, moving forwardly from one end of the channel, at the end point of each segment, a total score is calculated by adding to the score of that segment a best score occurring before the start point of the segment. If the total score exceeds a present value of a best string score for nonoverlapping segments, the present value of the best string score is replaced by the new total score, otherwise the present value of the best string score is retained. When the other end of the bay is reached, moving back towards the first end, segments are assigned to the channel for which the total score therefor exceeded the then-present value of the best string score and which do not overlap already-assigned segments.

Bay packing method and integrated circuit employing same

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Essex Junction, VT, United States of America

Keith W Lallier