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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
    #1
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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
     
    Alex Johnson, Oct 8, 2004
    #2
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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
    #3
  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
    #4
  5. Isaac Gerg

    Alex Johnson Guest

    Itanium (Merced): 10 stages
    Itanium 2 (McKinley and Madison): 8 stages
     
    Alex Johnson, Oct 8, 2004
    #5
  6. Isaac Gerg

    Grumble Guest

    http://intel.com/design/itanium2/manuals/25111003.pdf
    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
    #6
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