Using cone structures for circuit partitioning into FPGA packages

Circuit designers and high-level synthesis tools have traditionally used circuit hierarchy to partition circuits into packages. However hierarchical partitioning can not be easily performed if hierarchical blocks have too large a size or too many I-Os. This problem becomes more frequent with field-programmable gate arrays (FPGAs) which commonly have small size limits and up to ten times smaller I-O pin limits. An I-O bottleneck often occurs which during circuit partitioning means more required packages and more ordinary signal wires crossing between the packages. More critical timing paths between packages are cut and circuit operational frequencies are drastically reduced. In this paper, two new partitioning algorithms are presented that use cone structures to partition large hierarchical blocks into FPGA´s. Cone structures are minimum cut partitioning structures for netlists with low fanout, and clustering structures for partitioning netlists with high fanout. Cone structures also allow for full containment of critical paths. When used with good merging and cutting strategies, results show the cone partitioning algorithms given here produces fewer FPGG partitions than min-cut with good performance