Retiming with Interconnect and Gate Delay

  • Authors:
  • Chris Chu;Evangeline F. Y. Young;Dennis K. Y. Tong;Sampath Dechu

  • Affiliations:
  • Iowa State University, Ames;The Chinese University of Hong Kong;The Chinese University of Hong Kong;Micron Technology, Inc., Boise, ID

  • Venue:
  • Proceedings of the 2003 IEEE/ACM international conference on Computer-aided design
  • Year:
  • 2003

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Abstract

In this paper, we study the problem of retiming of sequential circuitswith both interconnect and gate delay. Most retiming algorithms haveassumed ideal conditions for the non-logical portions of the datapaths, which are not sufficiently accurate to be used in high performancecircuits today. In our modeling, we assume that the delay ofa wire is directly proportional to its length. This assumption is reasonablesince the quadratic component of a wire delay is significantlysmaller than its linear component when the more accurate Elmore delaymodel is used. A simple experiment is conducted to illustrate thevalidity of this assumption. We present two approaches to solve thisproblem, both of which have polynomial time complexity. The firstone can compute the optimal clock period while the second one isan improvement over the first one in terms of practical applicability.The second approach gives solutions very close to the optimal (0.13%more than the optimal on average) but in a much shorter runtime.A circuit with more than 22K gates and 32K wires can be optimallyretimed in 83.56 seconds by a PC with an 1.8GHz Intel Xeon processor.