Processor TDP - Base vs Turbo Frequency?

Discussion in 'MacBook Pro' started by shoehornhands, Jun 18, 2015.

  1. shoehornhands macrumors regular

    Joined:
    Oct 9, 2014
    #1
    What exactly does processor TDP refer to? I have an i7-4870HQ in my 15" MBP with a TDP of 47W. If I really push the processor though, it jumps up to 60W with turbo (and almost instantaneously goes from ~40 °C to > 90 °C).

    Is TDP in reference to the base frequency (i.e. 2.5GHz in the i7-4870HQ)? I certainly realize these processors aren't designed (with a MacBook Pro anyway) to run at the turbo frequency on multiple cores for any extended period of time. I'm just curious what exactly it's referring given that 60W is significantly higher than 47W.
     
  2. shoehornhands thread starter macrumors regular

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    Oct 9, 2014
    #3
    Thanks, sounds like it's more or less, just another marketing gimmick and TDP probably doesn't mean anything in relation to base and turbo frequency (given that there's no real standard as to what constitutes a real application / typical operation).

    Note to self: when in doubt, a safe bet is always "marketing gimmick."
     
  3. leman macrumors G3

    Joined:
    Oct 14, 2008
    #4
    Its not a marketing gimmick. It is a very clearly defined, important design parameter. But its certainly true that you won't be able to infer much about CPU's performance just from the TDP, you'd need have deep understanding for its architecture and the relationship between frequency and power usage.
     
  4. RoboWarriorSr macrumors 6502a

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    Feb 23, 2013
    #5
    The TDP is very important but shouldn't be a concern for the normal consumer, it's especially important for manufacturers when building thermally constrained devices like laptops. Generally higher TDP mean a more powerful CPU in the same generation. Honestly I haven't seen TDP be used in marketing since it would actually confuse the consumer more and will cause more problems than sales.
     
  5. shoehornhands thread starter macrumors regular

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    Oct 9, 2014
    #6
    Thanks for the info. I was going by that wikipedia link where it says:

    "For example, while a processor with a TDP of 100 W will almost certainly use more power at full load than a processor with a 10 W TDP from the same manufacturer, it may or may not use more power than a processor from a different manufacturer that has a 90 W TDP"

    It seems to me like TDP would only really be useful when comparing processors from the same manufacturer. For example, if Apple designs a MBP cooling system that can adequately cool a i7-4870HQ, then they know the cooling system can adequately cool other Intel processors with <= 47 W TDP as well.

    They couldn't design a cooling system based on Intel's TDP figure alone though (they would have to physically possess at least one chip of a given TDP to gather actual data, given that the process by which TDP is determined is somewhat arbitrary).

    The mention of AMD previously reporting the maximum power consumption as TDP is the reason I was thinking about it from a marketing perspective (it says Intel deviated from this and also introduced a new metric called SDP, perhaps to aid in marketing their processors as more efficient).

    I'm just speculating though.
     
  6. ha1o2surfer macrumors 6502

    Joined:
    Sep 24, 2013
    #7
    So TDP is the spec that laptop manufactures use to design their heatsink that Intel has set. Apple almost never follows this rule and that is rule is the heatsink should be able to dissipate 47 watts without hitting 105c(this temp depends on CPU), thus throttling. The CPU is allowed to turbo up to a certain multiplier which is set by either Intel or the EFI/BIOS of the laptop. There spec is called turbo time and it's set in seconds by Apple or Intel. Max is 72 seconds for laptops that do not have the TDP set higher. If the TDP is set higher than 47 watts then the CPU will turbo for longer or forever given the temps are not above 105c. Does that make sense? My 3840QM in my non Apple laptop will turbo up to 72 watts at 4.1Ghz forever as the cooling system is adequate. Does that answer your question? :)
     
  7. throAU macrumors 601

    throAU

    Joined:
    Feb 13, 2012
    Location:
    Perth, Western Australia
    #8
    Yeah TDP is more to do with cooling.

    If you have a 45 watt TDP processor, you really should be ensuring that the cooling in your machine can cope with that heat output. Or it will be constantly throttled

    "Turbo" allows the processor to exceed its regular design TDP/clock speed whilst cooling is sufficient (which a given machine may or may not be able to sustain depending on how good it's cooling is, and what the ambient temperature is). The regular clock speed is what your CPU is guaranteed to be able to run at if put in a machine that can cope with it's TDP.

    A machine that can handle say, 40 watt TDP with its cooling isn't good enough for a 45 watt TDP processor (e.g., an i5/i7 quad core), but will be able to run a 28 watt TDP processor on turbo quite well.
     

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