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Subnormal floating-point numbers are expensive on Intel processors

69 points · 54 comments · zdw

  1. rf15 · · focus · HN ↗
    ...Is this running extra micro code to fix some hardware bug/unreliability? How can this happen? Doesn't look like a normal design decision.
    1. duped · · focus · HN ↗
      It's to satisfy IEEE 754 and it's been this way for decades.
      1. pohl · · focus · HN ↗
        Does that mean that the ARM processors in the writeup are not satisfying IEEE 754?
        1. tasty_freeze · · focus · HN ↗
          It probably means Apple spent the silicon to handle subnormals at full speed in hardware, rather than triggering a slow microcode handler for such numbers.
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