A fanout optimization algorithm based on the effort delay model

This paper presents LEOPARD, a Logical Effort-based fanout OPtimizer for ARea and Delay, which relies on the availability of a (near) continuous size buffer library. Based on the concept of logical effort in VLSI circuits, the proposed algorithm attempts to minimize the total buffer area under the required time and input capacitance constraints by constructing the fanout tree topology and assigning the buffer sizes. More precisely, the proposed algorithm produces the optimum fanout tree solution if the fanout tree topology is restricted to a chain of buffers. For the case that a discrete size library of buffers is available, this paper also presents a post-processing (buffer merging) step that transforms the continuous buffer sizing solution to a discrete one while minimizing the round-off error. Experimental results show that compared to previous approaches, both for continuous and discrete buffer libraries, LEOPARD achieves a significant reduction in the total buffer area subject to the required time constraints.