Date of Award
Master of Science
Dr. Naveed Sherwani
Dr. Alfred Boals
Dr. Ajay Gupta
Masters Thesis-Open Access
In this thesis, we introduce a new class of cell models called Middle Terminal Models (MTM) which combines the advantages of existing cell models: BTM and CTM. This class contains the models 2MTM, 3MTM-V, and 3MTM+V depending on the number of metal layers and the permissibility of vias in over-the-cell areas. In MTM, two rows of terminals are located in the middle of the cell. This partitions over-the-cell area into three regions and allows allocation of more nets to over-the-cell area in congested channels. We prove that when vias are allowed over-the-cell, in "almost all" cases the MTM based layouts have smaller overall height as compared to the layouts based on the existing cell models.
We have implemented two MTM routers: MTM+V and MTM-V. MTM-V router, which does not allow vias in over-the-cell areas, is based on two key algorithms. First, we develop an approximation algorithm to select a planar set of nets of routing between two terminal rows of a cell row. Second, we develop an optimal algorithm for planar routing between the terminal row and the cell boundary. MTM+V router, which allows vias in over-the-cell areas, is based on two key algorithms: an optimal algorithm for terminal row selection and a greedy routing algorithm for over-the-cell and channel routing.
Experimentally, MTM based layouts are significantly better than the layouts based on existing cell models, irrespective of permissibility of vias over-the-cell.
Bhingarde, Siddharth, "Middle Terminal Cell Models for Efficient Over-the-Cell Routing" (1993). Master's Theses. 798.