It Takes Six Ones To Reach a Flaw

  • Authors:
  • T. Coe;P. T. P. Tang

  • Affiliations:
  • -;-

  • Venue:
  • ARITH '95 Proceedings of the 12th Symposium on Computer Arithmetic
  • Year:
  • 1995

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Abstract

The intial release of the Pentium processor has a flaw in its radix-4 SRT division implementation. It is widely-known that five entries were missing in the lookup table, yielding reduced-precision quotients occasionally. In this paper, we use mathematical techniques to analyze the divisors that can possibly cause failures. In particular, we show that Bits 5 through 10 (where Bit 0 is the MSB) of such divisors must be all ones. This result is useful in compiler-level software patches for systems with unreplaced chips; and we believe that the techniques used here are applicable in analyzing SRT division as well as other hardware algorithms for floating-point arithmetic.