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Re: Execution Speed - Elf II

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  • cdp1861
    Hi! Most instructions need two cycles or 16 clocks, but there are some like C0 XX XX which need three cycles (24 clocks). Richard ... Then
    Message 1 of 3 , Nov 28, 2002
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      Hi!

      Most instructions need two cycles or 16 clocks, but there are some
      like C0 XX XX which need three cycles (24 clocks).

      Richard

      --- In cosmacelf@y..., "bill_rowe_ottawa" <bill.rowe@r...> wrote:
      > Can anyone clarify the instruction execution speed of the ELF for
      > me? As I understand it the clock speed was effectively 1.79MHZ.
      Then
      > at 8 clock cycles per cpu cycle that's 223K cycles per second or
      > 111,500 or so instructions per second. Does that seem right?
    • Lee Hart
      ... Basically, yes. The 1.79 MHz clock frequency is right. Each CPU cycle takes 8 clock cycles, so they are all 1.79 MHz / 8 or 223,750 per second. Most
      Message 2 of 3 , Nov 28, 2002
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        bill_rowe_ottawa wrote:
        >
        > Can anyone clarify the instruction execution speed of the ELF for
        > me? As I understand it the clock speed was effectively 1.79MHZ. Then
        > at 8 clock cycles per cpu cycle that's 223K cycles per second or
        > 111,500 or so instructions per second. Does that seem right?

        Basically, yes. The 1.79 MHz clock frequency is right. Each CPU cycle
        takes 8 clock cycles, so they are all 1.79 MHz / 8 or 223,750 per
        second. Most instructions have one fetch and one execute cycle; for
        them, the instruction rate is thus 223,750 / 2 = 111,875 per second. But
        a few instructions have one fetch and two execute cycles; thus their
        instruction rate is 223,750 / 3 = 74,583 per second.

        So the exact instruction execution rate is somewhere between these two
        extremes, depending on the mix of 2-cycle and 3-cycle instructions.
        --
        Lee A. Hart Ring the bells that still can ring
        814 8th Ave. N. Forget your perfect offering
        Sartell, MN 56377 USA There is a crack in everything
        leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
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