reference slack distribution is calculated the intercorrelation function between two slack distributions p 1 s and p 2 s is defined in equation 4 below this intercorrelation function has an absolute maximum for a particular value of t this maximum is compared to the datapoint cp t 0 from the reference slack distribution if there is a significant mismatch a different parasitic estimation model must be selected and all design steps required for creation of design database and reference design database must be repeated co pending patent application ser no 09 946 240 illustrates the calibration method applied to the parasitic estimation model as shown in co pending patent application ser no 09 946 240 slack distribution resulting from embedded timing analysis performed on the design database is compared with the reference slack distribution from reference the timing analysis performed on the reference design database in case where n sub blocks in the design database correspond to one block in reference design database the slack distribution represents a collapsed slack distribution corresponding to the collapsed slack distribution a determination is made if the intercorrelation function has its maximum at t 0 if the maximum is at t max where t max is different from zero a global scaling factor a shift is applied to the parasitic estimation model embedded timing analysis is performed again based on the scaled parasitic estimation model the new slack distribution.