Patent ID: 7331027

Claim:
A method performing metal-only engineering changes in a design comprising the steps of: making the preliminary design changes in a metal-only process to change the existing design and perform an engineering change only (ECO) place and wire change to ensure that only wire changes can be made to the design, and for timing violations, determining which violating books of the existing design are contributing to said timing violations and creating an incumbent list of violating books which are contributing to timing problems of the design because of one or more of: slowness, poor gains, bad slews, and poor location violations and identifying these violating books as incumbent list books, determining a replacement book for each violating book by creating a candidate list of replacement books having improved factors because of one or more of: distance, slack, gain and slew from within the existing design, and swapping incumbent books with said replacement books of the candidate list to make the best swap for each book swapped from within an existing design with only wire changes to the design to improve a path having the said timing violation after comparing slews, gains, slacks and locations of these swapped books with those of the incumbent list and fixing those on the incumbent list by propagating a new critical timing path to swapped candidate books with a metal only fix which does not break the timing of the path involving incumbent books.