Extreme Area-Time Tradeoffs in VLSI

  • Authors:
  • Binay Sugla;David A. Carlson

  • Affiliations:
  • AT&T Bell Labs, Holmdel, NJ;Supercomputing Research Center, Bowie, MD

  • Venue:
  • IEEE Transactions on Computers
  • Year:
  • 1990

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Abstract

Consideration is given to the layout of bounded fan-in and fan-out prefix computation graphs in VLSI, and it is shown that the area requirements of such graphs exhibit this interesting property. A small constant factor reduction in time of computation from 2 log eta to log eta increases the area required to embed an eta node prefix computation graph significantly from O( eta log eta ) to Omega ( eta /sup 2/). The area requirements are also given. This behavior is an example of an extreme area-time tradeoff in VLSI. Since prefix computation also models the carry computation in a carry look-ahead adder, the same behavior is observed in the area requirements of a near-minimum computation time carry look-ahead adder. The authors also present circuits which meet the derived lower bounds for all values of T between log eta and 2 log eta .