The Pentium division flaw
The Intel Pentium(TM) processor for IBM compatible PC computers was first introduced into the market in May of 1993. A year later after an estimated two million had been sold it was discovered that there was a flaw in the hardware floating point division unit causing it to return incorrect results in very rare instances.

For example: 5506153.0 / 294911.0

      Correct: 18.67055823621364
      Pentium: 18.66990719233938

It is quite interesting to study the details behind the flaw, as it brings together many aspects of computer science. Includes a detailed description of the radix 4 SRT division algorythm used by the Pentium.

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Today's flawed divisor is:
David Deley: