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Itanium float vs int performance

Discussion in 'Intel' started by Isaac Gerg, Oct 7, 2004.

  1. Isaac Gerg

    Isaac Gerg Guest

    I heard a rumor that floating point operation the the 64bit Itanium
    processors perform faster than integer operations. I do not see how
    this is possible. Can someone enlighted me? I would appreciate it. If
    this is not true, I want to put these rumors to rest among my colleages.

    Thanks in advance!
    Isaac Gerg, Oct 7, 2004
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  2. Isaac Gerg

    Alex Johnson Guest

    About Itanium 2: "The resources consist of six integer units, six
    multimedia units, two load and two store units, three branch units, two
    extended-precision floating-point units, and two additional
    single-precision floating-point units."

    I don't know what you mean by "faster" at floating point than integer.
    They run on the same clock through the same pipeline. There are more
    integer units. Itanium 2 scores higher in SPECfp than SPECint, because
    these benchmarks are representations of how many times faster your
    computer is compared to a Sun Ultra 5 with a 300MHz processor, and that
    machine was especially poor at floating point compared to integer. So a
    balanced system would get higher SPECfp numbers than SPECint numbers.

    Alex Johnson, Oct 8, 2004
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  3. Isaac Gerg

    Grumble Guest

    Maybe he meant FP ops have a longer latency than integer ops?
    But it does not matter much since they are fully pipelined.
    Grumble, Oct 8, 2004
  4. Isaac Gerg

    Isaac Gerg Guest

    The last comment answered my question. Speaking of piplines, how long is
    the pipline on these chips?
    Isaac Gerg, Oct 8, 2004
  5. Isaac Gerg

    Alex Johnson Guest

    Itanium (Merced): 10 stages
    Itanium 2 (McKinley and Madison): 8 stages
    Alex Johnson, Oct 8, 2004
  6. Isaac Gerg

    Grumble Guest

    Itanium 2 Reference Manual for Software Development and Optimization
    Appendix A - Itanium 2 Processor Pipeline

    Listen up Intel: could you, please, allow content extraction on your
    Itanium PDF documents?
    Grumble, Oct 8, 2004
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