USB cool pad=+power drawn=+cpu throttling down?

Discussion in 'MacBook Pro' started by EtherealMAC, Nov 24, 2011.

  1. EtherealMAC macrumors member

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    Jan 26, 2011
    #1
    Hi guys!

    I own a targus cooling pad designed for macs:

    http://reviews.cnet.com/cooling/targus-chill-mat-for/4505-9990_7-33352014.html

    Been using it on my 17" inch MBP since about 2 years ago. It works reasonably well, maybe moreso because of the angle it puts the screen in respect of the MBP body (opening up the exhaust vents on the exact sweet spot where they are wide open) than because of its fans. Also, its basically a mesh that allows the aluminiun bottom to have lotsa space free of contact with surfaces that would hamper heat dissipation.

    Anyway, I agree that wahtever help cooling pads for MBPs bring is marginal, still for me it has aways been something "to have better than not - can't hurt to use it!", I have always thought that whatever little help for th eongevity of the logic board is good.

    Therein the crux of this post:

    It is well known that the MBP ac adaptor supplies less power than needed by a MBP in full load (audio/video processing, gamng) ... resorting to drawing from the battery to supply the rest of the power. Moreover, MBPs ( specially the sandy bridge ones), would throttledown the cpu speed if in lack of power or reach high temps right?

    So, if so, then would powering a usb cooling pad whilst audio/video work or gaming mean that the cpu would more likely get throttled down?

    Thanks in advance
     
  2. Queen6, Nov 24, 2011
    Last edited: Nov 24, 2011

    Queen6 macrumors 603

    Queen6

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    #2
    No, the CPU throttles due to temperature not power. So far the best results I have had for cooling is passive; RainDesign's iLap & Mstand. I did try some powered coolers (fans) only what I observed was that some aspects of the MacBook Pro ran cooler and the notebook's fans did reduce in RPM, however this resulted in a slightly higher CPU temperature, this was with a MacBook 4.1, A1260, Early 2008 2.4 Ghz C2D.

    As yet I have not tried the same with the new MacBook Pro 8.2 Core i7 2.4, although after reading this thread I may give a shot and see what happens...

    Look at this thread it may help you http://forums.macrumors.com/showthread.php?t=962504
     
  3. thundersteele macrumors 68030

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    Switzerland
    #3
    It's unclear whether the MBP throttles also due to lack of power. Some people have reported the battery being drained (slowly) while plugged in when doing heavy lifting. So I wouldn't expect too much throttling, but other sources have reported otherwise.

    You can always use the cooler as a laptop stand, without plugging it in.
     
  4. Queen6 macrumors 603

    Queen6

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    #4
    I never observed my Early 2008 MacBook Pro throttle due to a lack of power, ie battery draining, my new Late 2011 Core i7 2.4 I have yet to really push, so far it has run very cool, however I am still in the process of loading Apps and data.

    Once I get everything onboard I will be hitting it hard and see exactly what the MBP 8.2 can deal with...
     
  5. grahamnp macrumors 6502a

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    Jun 4, 2008
    #5
    I've noticed battery drain but no performance hit while the battery is draining so I suppose it is configured to run at full power even when power draw exceeds what the MagSafe and deliver. In any case, I've never found cooling pads to be effective on the MBP. Giving the bottom of the laptop ventilation does, but fans don't make a difference because the bottom has no vents so maybe try running your cooler as a passive stand?
     
  6. happle macrumors 6502a

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    Jun 20, 2010
    #6
    run your cooler through a powered usb hub...then you get the best of both worlds. the fan will still work but it wont suck any power from your mac.
     
  7. EtherealMAC thread starter macrumors member

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    Jan 26, 2011
    #7
    It does make complete sense that besides heat reasons, the sandy bridge MBP may get their CPU throttled down due to the AC adaptor ONLY supplying 85 V when an MBP in FULL GPU AND CPU LOAD would consume way over 90 V. There is a whole thread about it somewhere here in macforums, However, now that I think of it, since when under full load and plugged in the MBPs draw lotsa power from the battery (evidenced by the battery meter going down VERY slowly) I guess that PLUGGED IN+ FULL CPU & GPU LOAD+ USB powered cool pad = battery getting depleted faster. I guess the real question is how much the 0.5 V that the usb cool pad draws would matter in terms of the battery draining faster.

    Is my logic right or am I completely off?
     
  8. miles01110 macrumors Core

    miles01110

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    #8
    It's probably better to talk about power draw in terms of Watts instead of Volts. Volts are typically not discussed in terms of being "supplied" ; it's just a difference in electrical potential.
     
  9. EtherealMAC thread starter macrumors member

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    Jan 26, 2011
    #9
    Yeah, sorry. I'm completely clueless about electrical stuff. I'm sure I learned the difference between watts and volts in high school, but then went on studying humanities and it all got forgotten somehow.

    So, then, using a usb cool pad would not significantly contribute to cpu throttiling?
     
  10. Queen6 macrumors 603

    Queen6

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    #10
    No, nor do they work effectively with Mac`s you are far better to use a passive cooler like Rain`s iLap or Mstand. when you use a powered cooler on a Mac portable all you do is cool the outer case, this in turn results in the fan RPM reducing and the CPU/GPU running hotter.

    Apple`s algorithm for cooling depends on many factors and sensors throughout the system. Forcing higher fan speed will reduce temperatures under moderate load and slow down the onset under high loads, this is about as much as you can do, SMC fan control is excellent for this.

    I have observed this for all Apple portables, and both my MacBook Pro 4.2 & 8.2 react exactly the same, if you use anything the cools externally (cooler pad, desk fan) it fools the system into reducing fan speed and CPU & GPU temperatures can in turn increase as much as 10C over using the Pro with a passive cooler and higher fan RPM`s.

    YMMV
     
  11. EtherealMAC thread starter macrumors member

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    #11
    Ah! But I don't have this problem cuz when on full load, I put SMC fan controller in OS Lion ( Lubbo's fan when in Bootcamp). This way I assure that the fan will not run any less than 4000 rpm when I KNOW the computer will be using the cpu and gpu to its fullest, 6000 rpm if its goes over 80 C.

    The usb powered targus chill mat indeed, as you say, cools the case via two ways: a) as a passive cooler due it its angled shape/mesh design and b) by the fans pumping cold air on the bottom plate of the case directly on the area where it gets the hottest. So, this mat plus SMC fan control or Lubbo's I THINK will contribute to the longevity overall of the machine. However, I got applecare so not that worried on it dying on me within the next 3 years.
     
  12. Queen6, Nov 28, 2011
    Last edited: Nov 28, 2011

    Queen6 macrumors 603

    Queen6

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    #12
    Agreed there is little negative in keeping the system cool, same here I use smc fan control to preempt high temperatures, as it is far easier to keep a Notebook cool, than cool a hot machine.

    I dont worry so much about premature failure as the system components are well within range, more that the fans at full speed can be distracting. I always try to use my MBP`s on a pad or riser.

    The Moshi Zephyr-2 is specifically deigned for Mac`s, unfortunately it`s pricing and availability rather put it outside of the give it a shot group, and I have yet to observe a powered cooler make a significant positive effect on the internals of an Apple portable.

    Full load I am seeing around 77C, so far :p MBP 8.2, Core i7, 2.4
     

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