International Business Machines Corporation

Kevin M McIlvain

James J Curtin

Douglas S Search

Ray Raphy

Stephen K Szulewski

Michael J Cadigan, Jr

Jose Luis Neves

Edward J Hughes

Genie is a described computer chip design tool which can analyze the data contained within an entire endpoint report, compute relationships between paths based on shared segments, and display this information graphically to the designer. Specifically, Genie groups failing paths into Timing Islands. A timing island is a group of paths which contain at least one shared segment. The most frequently shared segment is sifted to the top of the priority list for each island, and is labeled as the Hub. Thinking of timing islands as a tree, the hub of the island would be the trunk. If you chop the tree down by the trunk, all of the branches, limbs and twigs will fall down too. This is analogous to fixing the timing failures in the hub, and the fix trickling out to each of the segments that dangle off the hub.

Genie: a method for classification and graphical display of negative slack timing test failures

More 'timing closure efficient' Timing Driven Placements by implementing our new net weight for negative slack paths to enhance timing closure behavior is provided by a NSRF (Negative Slack Recover Factor). This new weight would not be based on the absolute amount of negative slack in a path, but rather it would be based on the proportion or percentage of the path's total net delay adder that must be recovered in order to achieve timing closure (zero slack). After an initial or previous placement has been created, then a list of paths with timing violations with a Negative Slack Recover Factor (NSRF) is created for each net in each of the timing paths on the list of paths, and then calculating a NSRF net weight factor for use in subsequent placements and also assigning nets in the list of paths with no timing violations a NSRF default value of one. The NSRF value is calculated as equaling (ZWLM slack value+negative slack value)/ZWLM slack value=(1+(negative slack value/ZWLM slack value)), where ZWLM is a Zero Wire Load Model (ZWLM) value of timing wherein all wire parasitics are removed from consideration in the timing.

Negative slack recoverability factor&#x2014;a net weight to enhance timing closure behavior

A circuit design method utilizes existing late mode worst case slack calculation functions inherent in timing path trace algorithms which only need to record the worst arrival and worst required arrival times at each netlist node as traced paths. Because of this, most individual path tracing is curtailed due to the likelihood that a more critical arrival or required arrival time has already been recorded at a given netlist node. Worst case slacks are then determined by subtracting the worst case arrival time from the worst case required arrival time. In this manner, worst case slack values are calculated for the entire netlist within a reasonable amount of time. The method uses these existing functions by querying the worst case slack at each netlist node under varied timing model scenarios. These varied timing model scenarios include altering the cell and net delays and arrival times in the model. Then, with the worst case slacks from the varied timing model scenarios in hand, the required priority factors, recoverability and path composition factors are computed by comparing the differences in the worst case slack at each netlist node.

Method for netlist path characteristics extraction

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Kevin M McIlvain