Why call the i5 CPU 1.7Ghz ?

Discussion in 'MacBook Air' started by OSMac, Aug 1, 2011.

  1. OSMac, Aug 1, 2011
    Last edited: Aug 1, 2011

    OSMac macrumors 65816

    Jun 14, 2010
    In the past Intel would quote a CPU's maximum speed,
    a "2.4GHz Core 2 Duo" would run 2.4GHz at most
    or clock down to lower speeds when needed.

    Now with the 13's i5 for example Intel calls it a 1.7Ghz chip.
    Yet it seldom, if ever, even runs a 1.7GHz.

    Most of the time it idles at about 800Mhz
    and then turbos up to 2.4GHz under dual core load
    or 2.7GHz under single core load.

    Apple's marketing never even mentions the turbo speeds
    and Intel labels it a i5 1.7GHz CPU ?
  2. KPOM macrumors G5

    Oct 23, 2010
    Intel now advertises the base speeds of its processors, since those are the speeds it will operate under maximum load. Turbo Boost speeds are only activated for short periods of time as operating them at those speeds for an extended time would exceed the advertised TDP.
  3. gnasher729 macrumors P6


    Nov 25, 2005
    1.7 GHz means: This chip can run with all cores used for an unlimited amount of time at 1.7 GHz without any damage to the chip and without any damage to other hardware. So when you really need all the power that you can get, like running Handbrake overnight, 1.7 GHz is what you will get.
  4. OSMac, Aug 1, 2011
    Last edited: Aug 1, 2011

    OSMac thread starter macrumors 65816

    Jun 14, 2010
    Most of the time it idles at 800MHz or so if your just browsing,
    then ramps up to 2.4GHz say when encoding a video.

    Why call it a 1.7GHz CPU?

    Try CPUz if you have Windows installed.
    Seems it stays at 2.4GHz under full dual core load, not 1.7?
  5. Mikael macrumors regular

    Aug 4, 2005
    Gothenburg, Sweden
    The thing is that if you keep it running at full load, it may eventually have to back down to 1.7GHz so that it doesn't get too hot. Intel guarantees that as long as there is a cooling solution in place able to dissipate 17W of thermal power, the CPU will never go lower than 1.7GHz under full load. That's why it's called a 1.7GHz CPU.
  6. KPOM macrumors G5

    Oct 23, 2010
    I ran a Handbrake test in Windows the weekend before last and had CPU-z installed. My i7 fluctuated between 2.6GHz and 1.8GHz most of the time (occasionally dropping down to 1.4GHz, and 800MHz when it was completely idle). It spent more time at 2.6GHz in the beginning, and a bit less at the end. I'd say it spent about half the time at each speed.

    I'm guessing Intel's lawyers advised it to advertise the base speed rather than the boosted speed. Otherwise, someone would sue them for false advertising since their "2.9GHz Core i7" (the maximum turbo boost in single core mode) or even their "2.6GHz Core i7) (maximum turbo boost in dual core mode) runs at 1.8GHz when fully taxed.
  7. OSMac thread starter macrumors 65816

    Jun 14, 2010
  8. mac jones macrumors 68040

    Apr 6, 2006
    I think it's sort of a compromise thing.

    First they made chips that ran at one speed.

    Then they made chips that throttled 'down' so they could save on battery life.

    Then they made chips (i5/i7) that throttle 'up and down' to circumvent heat problems and also save on the battery.

    I'm sure they would love to sell them at max rated GHZ, but it's just a throttle, not steady state.

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