Regular, area-time efficient carry-lookahead adders

Tin Fook Ngai, Mary Jane Irwin, Shishpal Rawat

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


For fast binary addition, a carry-lookahead (CLA) design is the obvious choice (S. Ong and D. E. Atkins, Proc. Sixth Symposium of Computer Arithmetic, Aarhus, Denmark, June 1983; M. A. Bayoumi, G. A. Jullien, and W. C. Miller, INTEGRATION 1 (1983)). However, the direct implementation of a CLA adder in VLSI faces some undesirable limitations. Either the design lacks regularity, thus increasing the design and implementation costs, or the interconnection wires are too long, thus causing area-time inefficiency and limits on the size of addition. R. P Brent and H. T Kung (IEEE Trans. Comput. C-31 (Mar. 1982)) solved the regularity problem by reformulating the carry chain computation. They showed that an n-bit addition can be performed in time O(log n), using area O(n log n) with maximum interconnection wire length 0(n). In this paper, we give an alternative log n stage design which is nearly optimum with respect to regularity, area-time efficiency, and maximum interconnection wire length.

Original languageEnglish (US)
Pages (from-to)92-105
Number of pages14
JournalJournal of Parallel and Distributed Computing
Issue number1
StatePublished - Mar 1986

All Science Journal Classification (ASJC) codes

  • Software
  • Theoretical Computer Science
  • Hardware and Architecture
  • Computer Networks and Communications
  • Artificial Intelligence


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