Abstract: A cell placement for an integrated circuit chip comprises a large number of cells allocated to respective locations on the surface of the chip. The placement is divided into switch boxes that surround the cell locations respectively. A bounding box is constructed around each net of a netlist for the placement. A congestion factor is computed for each switch box as being equal to the number of bounding boxes that overlap the respective switch box. A cost factor for the placement and associated netlist is computed as the maximum value, average value, sum of squares or other function of the congestion factors. The individual congestion factor computation can be modified to require that a pin of a net of one of the bounding boxes overlap or be within a predetermined distance of a switch box in order for the congestion factor to be computed as the sum of the overlapping bounding boxes in order to localize and increase the accuracy of the cost factor estimation.

Abstract: A computer implemented method for optimizing cell placement for integrated circuit design is provided herein. The method comprises the steps of segmenting an integrated circuit surface abstraction into a plurality of regions; assigning a plurality of cells to one of the regions; creating a list of said plurality of cells in order of decreasing cell height; reassigning said cells in order of the list such that the cells are assigned to said region until there is insufficient capacity to fit anymore of the cells into the region; and thereafter assigning the remaining cells outside of the region.

Abstract: A process for implementation on a programmed digital computer includes providing a placement of clusters of cells which are assigned to regions on an integrated circuit chip, and combining the regions to form region groups. The region groups collectively constitute a "jiggle" which resembles a sieve. The clusters in each region group are re-assigned to the regions in the region group. The regions are recombined to form different region groups (a different jiggle), and the clusters in each different region group are re-assigned to the regions in the different region group. These steps are repeated using at least two, preferably four different jiggles, until an end criterion is reached. Then, the regions and clusters are hierarchically subdivided, and the process is repeated for each hierarchical level until the clusters have been reduced to individual cells.

Abstract: In a physical design automation system for producing an optimized cell placement for an integrated circuit chip, a placement optimization methodology is decomposed into a plurality of cell placement optimization processes that are performed simultaneously by parallel processors on input data representing the chip. The results of the optimization processes are recomposed to produce an optimized cell placement. The fitness of the optimized cell placement is analyzed, and the parallel processors are controlled to selectively repeat performing the optimization processes for further optimizing the optimized cell placement if the fitness does not satisfy a predetermined criterion. The system can be applied to initial placement, routing, placement improvement and other problems. The processors can perform the same optimization process on different placements, or on areas of a single placement.

Abstract: A method for planning floor allocation of an integrated circuit to each function is disclosed. To provide enough core space to each of the functions and to meet some cost functions such as space utilization requirement of each of the functions, the disclosed method divides the core space to a grid of elementary regions. Then, pieces of the core space are defined and the pieces containing the borders and the overlapping areas of the functions are identified. Then, the identified pieces are used shift the allocated capacities of the functions as to shift excess capacity or core space from the functions with excess capacity to the functions with a shortage of capacity.

Abstract: A system for providing an optimal preplacement of cells on a bounded surface of a semiconductor chip is disclosed herein. A percentage of the cells have predetermined interconnections with other cells. The system initially locates the cells on said surface, then computes coordinates for interconnected cells, determines a weight associated with each cell, and calculates a new cell coordinate for each cell based on the coordinates and weights from said determining step.

Abstract: Several inventions are disclosed. A cell architecture using hexagonal shaped cells is disclosed. The architecture is not limited to hexagonal shaped cells. Cells may be defined by clusters of two or more hexagons, by triangles, by parallelograms, and by other polygons enabling a variety of cell shapes to be accommodated. Polydirectional non-orthogonal three layer metal routing is disclosed. The architecture may be combined with the tri-directional routing for a particularly advantageous design. In the tri-directional routing arraingement, electrical conductors for interconnecting terminals of microelectronic cells of an integrated circuit preferrably extend in three directions that are angularly displaced from each other by 60.degree.. The conductors that extend in the three directions are preferrably formed in three different layers. A method of minimizing wire length in a semiconductor device is disclosed. A method of minimizing intermetal capacitance in a semiconductor device is disclosed.

Abstract: An apparatus and method for locating a good approximation of optimal Steiner tree routing in the presence of rectilinear obstacles, including finding a Steiner tree on an escape graph. The escape graph is constructed by forming lines from given points (pins) and obstacles. Obstacles and the segments of obstacles are provided with lines parallel to that segment at a given minimum distance S.sub.min from the obstacle is constructed until it reaches either a boundary of an obstacle or a boundary of the core. For pins which do belong to a boundary of an obstacle, a ray, perpendicular to the segment of the boundary on which the pin is located is constructed from the pin and out from the obstacle until it reaches another obstacle or a boundary of the core. For pins which do not belong to an obstacle, vertical and horizontal lines are constructed. A Steiner tree may then be found on the escape graph by using any number of algorithms such as algorithm S and algorithm M.

Abstract: A method for maximizing effectiveness of parallel processing, using multiple processors, to achieve an optimal cell placement layout on an integrated circuit (IC) chip is disclosed. The method requires the cells of the IC to be assigned to one of the multiple processors in a manner to balance the work load among the multiple processors. Then, the affinity of the cells to each of the multiple processors is determined. The affinity of the cells, including the conflict reduction factors and work load balancing factors, is used to reassign the cells to the processors. The cell affinity calculation and the processor reassignment are repeated until no cells are reassigned or for a fixed number of times. The assignment of the cells to the multiple processors and subsequent reassignments of the cells based on affinity of the cells to the processors reduces or eliminates the problems associated with prior parallel cell placement techniques.

Abstract: An initial placement of cells for an integrated circuit chip is decomposed into a hierarchial order of groups of cells. The groups are routed simultaneously using parallel processors, and the results are recomposed to provide a global routing that provides a detailed mapping of cell interconnect congestion in the placement. Areas of high congestion are identified, and a congestion reduction algorithm is applied using the parallel processors to alter the placement in these areas simultaneously. The overall fitness of the placement is then computed, and if it has not attained a predetermined value, the steps of identifying congested areas and applying the congestion reduction algorithm to these areas are repeated. The cumulative error created by altering the placement without repeating the global routing is estimated, and if it exceeds a predetermined value, the global routing is also repeated.

Abstract: Several inventions are disclosed. A cell architecture using hexagonal shaped cells is disclosed. The architecture is not limited to hexagonal shaped cells. Cells may be defined by clusters of two or more hexagons, by triangles, by parallelograms, and by other polygons enabling a variety of cell shapes to be accommodated. Polydirectional non-orthogonal three layer metal routing is disclosed. The architecture may be combined with the tri-directional routing for a particularly advantageous design. In the tri-directional routing arrangement, electrical conductors for interconnecting terminals of microelectronic cells of an integrated circuit preferrably extend in three directions that are angularly displaced from each other by 60.degree.. The conductors that extend in the three directions are preferrably formed in three different layers. A method of minimizing wire length in a semiconductor device is disclosed. A method of minimizing intermetal capacitance in a semiconductor device is disclosed.

Abstract: A system for optimally locating cells on the surface of an integrated circuit chip is presented herein. The system comprises constructing a plurality of neighborhoods containing elements positionally related to one another; initially evaluating the lowest level of region hierarchy; iteratively developing a logical one-dimensional preplacement of elements on said surface; performing an affinity driven discrete preplacement optimization; evaluating whether a highest level of regional hierarchy has been attained; iteratively performing a dispersion driven spring system to levelize cell density and an unconstrained sinusoidal optimization; executing a density levelizing procedure; iteratively optimizing while controlling element densities; removing element overlap; iteratively optimizing for desired spacing between elements, adjusting element spacing, and permuting elements; locating elements on grid lines; and iteratively performing a functional sieve crystallization.

Abstract: A system for defining a cut point dividing a plurality of cells located on the surface of a semiconductor chip is disclosed herein. The surface has at least one region located thereon. The system comprises dividing each region into subregions, computing the capacity of each subregion, finding the maximum and minimum cell locations within each region, dividing the range spanning the maximum and minimum cell locations into a plurality of subintervals, calculating an index for each cell based on the subinterval containing the cell, accumulating cell heights for each subinterval, determining the values of cell heights for each region as the sum of cell heights for all prior regions, locating the minimum index such that the cell heights for each region are most closely proportional to the capacity of the associated subregion, and finding the cut line based on said minimum index and the maximum and minimum cell locations.

Abstract: A system for optimizing the density of cells located on a surface of a semiconductor chip divided into a plurality of rectangular regions is provided herein. The corners of these regions define nodes. The system comprises computing an average local cell density for regions adjacent to each node and deforming these regions by relocating nodes to positions that minimize a cost function associated with the densities of the new deformed regions bordering the relocated nodes.

Abstract: One or more non-overlapping moving windows are positioned over a placement of cells for an integrated circuit chip to delineate respective subsets of cells. A fitness improvement operation such as simulated evolution is performed on the subsets simultaneously using parallel processors. The windows are either moved to specifically identified high interconnect congestion areas of the placement, or are moved across the placement in a raster type pattern such that each area of the placement is processed at least once. Exchange of misplaced cells between subsets can be accomplished by dimensioning the windows and designing the window movement pattern such that the subsets overlap. Alternatively, such exchange can be accomplished by using two sets of windows of different sizes. As yet another alternative, the improvement operation can allow misplaced cells to move to a border area outside a window.

Abstract: A system for ascertaining the penalty associated with relocating a cell located on a surface of a semiconductor chip to an alternate location is disclosed herein. The system comprises a region capacity calculator for determining a capacity of cells which will fit in the current region, a height capacity calculator for determining the sum of heights for all cells located in each region, a basic penalty calculator which computes a basic penalty associated with relocating the cell to another location based on the capacity and heights of cells for the current region and the capacity and heights of cells in the proposed region, and a total penalty calculator for computing the total penalty associated with the basic penalty, penalties associated with multiple regions, and cell capacity for the current cell.

Abstract: Several inventions are disclosed. A cell architecture using hexagonal shaped cells is disclosed. The architecture is not limited to hexagonal shaped cells. Cells may be defined by clusters of two or more hexagons, by triangles, by parallelograms, and by other polygons enabling a variety of cell shapes to be accommodated. Polydirectional non-orthogonal three layer metal routing is disclosed. The architecture may be combined with the tri-directional routing for a particularly advantageous design. In the tri-directional routing arrangement, electrical conductors for interconnecting terminals of microelectronic cells of an integrated circuit preferrably extend in three directions that are angularly displaced from each other by 60.degree.. The conductors that extend in the three directions are preferrably formed in three different layers. A method of minimizing wire length in a semiconductor device is disclosed. A method of minimizing intermetal capacitance in a semiconductor device is disclosed.

Abstract: A method and apparatus for positioning a cell in a cell placement for an integrated circuit chip such that a total wirelength for interconnect nets that are connected to said cell is substantially minimum includes constructing bounding boxes around the interconnect nets with the cell excluded respectively. A median interval of the bounding boxes within which the total wirelength is substantially invariant is computed, and the cell is positioned in the median interval. Another optimization methodology, such as for minimizing interconnect congestion, is then applied to compute and position the cell in an optimum location in the median interval.

Abstract: A method for maximizing effectiveness of parallel processing, using multiple processors, to achieve an optimal cell placement layout of a core area of an integrated chip is disclosed. The method requires the core area to be divided into preferably a grid of rectangular regions. Then, the rectangular region is sequenced such that each region of the sequence is not adjacent to the previous or the next region of the sequence, and is sufficiently far from the previous and from the next region of the sequence such that when multiple processors are assigned to consecutive regions of the sequence to perform cell placement algorithms, area-conflicts are minimized eliminating the need to limit the distances the cells may be moved.

Abstract: A system for improving the position of cells located on a surface of a semiconductor chip having at least one region located thereon is disclosed herein. The system calculates affinities for relocating the cell to an alternate region, computes a first threshold, and repositions all cells having a maximum affinity greater than the first threshold to the region providing the maximum affinity for the cell.