On-chip interconnects modeling and timing driven buffer insertion

Abstract

With the increasing effect of on-chip interconnects on nowadays [sic] VLSI design performance, modeling of interconnects becomes a necessity. GAM, TPN, and AWE are well known methods that are used to map an interconnect to an equivalent electrical circuit. In this thesis, a general approach that considers z-parameters is developed witch allows the generation of equivalent RC, RLC, and RLCG circuits for both T and ∏ configurations. The performance of these generated circuits is compared to H-spice simulations by measuring the effect of interconnects on the transition times and delays under different conditions such as input transition times, interconnect lengths and capacitive loads. As a result, the a-configuration of AWE method reveals consistently an acceptable performance which makes it a good candidate to be utilized for buffer insertion.Buffer insertion is a popular technique used to reduce the delay of a long interconnect by segmenting it and inserting buffers among these segments. Therefore, the performance of this technique depends strongly on the accuracy of the considered interconnect model. However, using a model such as the RLCG of ∏ configuration which is derived from using the AWE method is not practical due to the complexity accompanied by such model which makes the derivation of closed-form expressions very complicated. To overcome this dilemma, the selected configuration has been mapped to a simple equivalent RC circuit. As a consequence, a new RC representation of on-chip interconnects is developed. Moreover, depending on the developed RC model, the proposed buffer insertion technique shows superiority over previously published works.