Does a 17" dissipate heat better than a 15"

Discussion in 'MacBook Pro' started by EtherealMAC, Nov 8, 2011.

  1. EtherealMAC macrumors member

    Joined:
    Jan 26, 2011
    #1
    DISCLAIMER: This question stems from my own common sense, but I dont know much about physics nor thermodynamics nor anything like that. So please bear with me ... if you have a major that would allow you explain the answer question, please do so.


    Ok so here's the question:

    When using high performace task such as gaming and video editing/processing (hence, using both the CPU AND THE GPU to its max) would a 17" MBP dissipate heat better than an equally spec'ed 15"? And even a 13"? (although I am more interested in the 17" vs 15" comparison, as a 13" would generate less heat due to the lack of a discrete GPU and less powerful CPU)

    My common sense tells me that theoretically, a 17'' would handle heat management better because of tow reasons:

    a) Its case has more space/volume, and therefore, stuff is less cramped than in a 15"
    b) Since the unibody aluminium casing in MBPs acts in itself as a heat sink/dissipator, then since there is much more of an aluminiun surface on a 17", then the more surface to serve asa heat dissipator.

    So, for those of you that are more saavy in physics than me, is my reasoning right? If not why not? If it is right, then : How much of a difference in heat dissipation would a 17" offer over a 15" ? Considerable? Negligible? Not that much that is even worth asking?

    Let the lecture begin
     
  2. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #2
    There shouldn't be much difference. The MBP doesn't depend on dissipation via aluminum to maintain safe temperatures. The venting at the rear is where the primary heat is discharged. Any heat radiated to the case is incidental. That is why you can safely operate in clamshell mode, with the lid closed.

    The Intel processors used in Macs are designed to automatically shut down to prevent damage if they truly overheat (around 100C/212F - 105C/221F, depending on your processor). iStat Pro will give you accurate readings of your temps, among other things.

    Unless there is a rare defect in your Mac, your temps are well within the normal operating range, considering the workload you're putting on it. Websites with Flash content, games and other multimedia apps will put higher demand on the CPU/GPU, generating more heat. This is normal. If you're constantly putting high demands on your system, such as gaming or other multimedia tasks, expect temps to rise and fans to spin up accordingly. It's just your Mac doing its job to maintain temps within the normal range.

    Your fans are always on when your Mac is on, spinning at a minimum of 2000 rpm (for MBPs) or 1800 rpm (for MBAs, MBs and minis). They will spin faster as needed to keep temps at a safe level. If they're spinning up without increased heat, try resetting the SMC. PRAM/NVRAM has nothing to do with these issues, so resetting it will not help. Also, make sure you don't block the vents, which are located at the rear, near the hinge.

    Learn about the fans in your Mac
    Apple Portables: Operating temperature

    There is not an overheating problem with Mac portables. There is only a perceived overheating problem. That's partly due to the fact that the aluminum casing transfers heat better than some other notebook materials, so they may feel hotter to the touch than notebooks made of other materials. It may even become hot enough to be uncomfortable to rest on your lap. This, too, is normal. Because a user is unfamiliar with the heat normally generated by a Mac portable doesn't mean there's a problem with the Mac. Only on rare occasions is there a defect that causes true overheating.
     
  3. EtherealMAC thread starter macrumors member

    Joined:
    Jan 26, 2011
    #3
    Hi GGJ, thanks for your post. Yes I've read this same info you are posting on some other thread, and I understand it but I feel it doesn't fully answer my question.

    If I understand your post well, isn't there a contradiction when you say:


    So, if indeed the aluminum casing serves as a heat dissipating mechanism (even if its an incidental one) then , if my understanding of physics is not too far off, the bigger the surface on whch heat is being disspated, the bigger this (incidental) heat sink is, and hence, the more the heat that is being dissipated via having the aluminun being in contact with the air.

    Another thing that derives from your post is that, yes, I know that the main heat exhaust comes from the vents at the back of the casing, that is a given, but again, if this exhaust vent is bigger on a 17 " than in a 15" ( which I think it is, correct me if I'm wrong, I don't have them both to compare) then by default the 17 inch will manage heat better than an equally specced 15 inch due to the bigger vent.


    So, my concern is not wheter the MBP gets hot or not, I know it does, I know why it does, and I have no problem whatsoever with it getting hot (I use a Targus cooling pad specifically designed for MBPs when I game on my lap). My concern is specifically wheter the 17" would manage heat better than a 15 inch.

    The ulterior reason why I am asking this is because, if the 17 inch does dissipate heat more than a 15", then the better the 'gpu-overclocking-prospect" a 17 inch has over a 15 inch when gaming in Win 7 64 bit bootcamp.
     
  4. thundersteele macrumors 68030

    Joined:
    Oct 19, 2011
    Location:
    Switzerland
    #4
    Apparently the answer is no, for early 2011 models at least.

    http://www.notebookcheck.net/Review...-GHz-quad-core-glare-type-screen.50346.0.html
    http://www.notebookcheck.net/Review...-GHz-quad-core-glare-type-screen.50344.0.html

    They have some extensive results on MBP temperatures under load and idle. The room temperature is a bit lower for the 15'' test, so maybe it's not a totally fair comparison. Still the result seems to be that the 15'' is slightly cooler under load, and very similar while idle.

    Another interesting fact is that the 2.0GHZ 15'' is cooler than the 2.2GHZ when idle. Under load they seem very similar.
     
  5. rev.b macrumors regular

    rev.b

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    May 1, 2009
    Location:
    Portugal
    #5
    I went from a 15" i5 2.4Ghz (DC) to a 17" i7 2.2Ghz (QD). There's a small difference in temperatures, but I notice fan speed is much lower in the 17".

    In sum, the temperatures seem about the same, but the 17" is MUCH quieter.
     
  6. Vantage Point macrumors 65816

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    Mar 1, 2010
    Location:
    New Jersey
    #6
    I have the 2010 15" i5 2.4 DC and am considering upgrading to the 15" base 2011 i7 2.2 QC. Should I expect significant or noticeably more heat and lower battery life in the latest MBP models? I love the current design and worry about apple changing the size to the 16:9 ratio or raising the standard resolution - which is to harsh on my eyes which is why I fear a future redesign. I could use the extra power but can live with what I have. I just don't want lower battery life or 'significantly' more heat and loud fans.
     
  7. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #7
    No, there's no contradiction. The MBP doesn't rely on heat dissipation via the aluminum chassis to maintain safe operating temperatures. Instead, it relies on the fans and vents located at the rear (which I believe are identical in size between the 15" and 17" models). The dissipation through the chassis makes it hotter to the touch for the user, so it's a user comfort consideration more than a heat management consideration.
     
  8. rev.b macrumors regular

    rev.b

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    Location:
    Portugal
    #8
    I don't know about the 15". My experience with this early 2011 17" is - less heat, less noise, and slightly better battery life.
     
  9. Vantage Point macrumors 65816

    Joined:
    Mar 1, 2010
    Location:
    New Jersey
    #9
    Thanks, that is helpful. But, my 2010 15" is quite (even with a faster drive) except when I have used handbrake. I am hoping for a good black friday price on Amazon like last year and if so then I will upgrade - that should give me plenty of power to hold me for 3 years.
     
  10. mape2k macrumors regular

    Joined:
    Apr 18, 2011
    Location:
    Germany
    #10
    The fans on the 17" are slightly larger than the ones for the 15". Source

    to the OP: Larger surface with identical material will results in better heat dissipation, that's common sense. However, as GGJstudios pointed out, MBPs don't rely mainly on heat dissipation to cool the hardware. Even though, the 17" should have a slight advantage because of the larger surface and larger fans.
     
  11. psykick5 macrumors 6502

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    Sep 4, 2011
    #11
    If the slit in the back is the place where hot air is ejected... isn't the slit in the 17" larger than the 15"?
     
  12. mape2k macrumors regular

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    Apr 18, 2011
    Location:
    Germany
    #12
    The slit might be larger, but what is more important is the size of the heatsink. Since the fans on the 17" are slightly larger than on the 15", it seems that also the heatsink is slightly larger.

    See here.
     
  13. thundersteele macrumors 68030

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    #13
  14. vitzr, Nov 9, 2011
    Last edited: Nov 9, 2011

    vitzr macrumors 68030

    vitzr

    Joined:
    Jul 28, 2011
    Location:
    California
    #14
    Yes it is.

    I am composing this on my 2011 15" MBP. My 17: is also on my desk, when aligning them (in lieu of a tape measure) the slit / black plastic cover at the rear of the 17" is approx. 35mm longer horizontally.

    My practical day to day experience when running under a heavy load, such as rendering and some design intense apps, the 17" is noticeably cooler and the very warm 15" MBP.

    Both my 15" and 17" are equally configured.

    Edit:
    Specific configurations for each:
    2.5GHz Quad-core Intel Core i7
    8GB 1333MHz DDR3 SDRAM — 2x4GB
    256 GB OEM SSD


    I highly prefer the 17", yet have certain specific uses for both. Overall if I had to get by with just one it would be the 17". It does indeed run cooler.
     
  15. EtherealMAC thread starter macrumors member

    Joined:
    Jan 26, 2011
    #15
    Thank you Mape2k and Vitzr, a confirmation that the vent exhaust and the fans are bigger on the 17 inch, as well as a side by side heat compariosn by exactly specced 17" and 15" is exactly the kind of info I was hoping for. TYVM!

    However, notebookcheck.net's thorough test does intrigue me, why would they find the 17" running hotter than the 15"?:



    Granted, the room where they tested the 15" was slightly colder than the 17", but again, if my physics are not that off, the cooler room doesn't justify such a difference they found on both the average temp as well as the peaks they found, specially on the specific areas of the casing where they got these peaks. Maybe their 17" was a lemon? Maybe in Apple's chinese factory they applied a little bit too much thermal paste on that specific machine? Any theories?

    Anyway, now that a kind macrumors forumer has confirmed that the 17" inch does run cooler than an equally specced 15", what implications does this have for overclocking the 17"'s GPU? Is it safe to sa that the 17" has a little tiny bit of more headroom for pushing the GPU further from its stock clocks speeds? There is a thread here is in this same forum about overclocking the current 15" and 17", check for yourself at:

    http://forums.macrumors.com/showthread.php?t=1142028

    So the question is not if it can be done safely, the guys on that forum found that it can be safely overclocked while making it run even cooler than from its stock speeds. The question is, would a 17" be better for overclocking? If so, how much better?
     
  16. vitzr macrumors 68030

    vitzr

    Joined:
    Jul 28, 2011
    Location:
    California
    #16
    Unfortunately, the company that builds the MacBook Pro's for Apple does a very inconsistent and sloppy job of applying thermal paste.

    One never knows what kind of quality they will receive as its' a crap shoot at best.

    Usually they use too much, huge gobs. I know, I've had over half of my many MBP's apart to remove the excess, clean up the mess, and re apply the proper amount of paste.

    This will result in a reduction in temps, and a much cooler, better running Mac.

    For the price you pay, this is the last thing one should have to do.

    I've bought an equal number of ThinkPads over the years and not once have had a problem.

    Sad but true.

    Here are a few for your reference:

    http://forums.macrumors.com/showthread.php?t=1105643

    http://forums.macrumors.com/showthread.php?t=969362

    http://forums.macrumors.com/showthread.php?t=1165928

    http://forums.macrumors.com/showthread.php?t=1190077

    http://forums.macrumors.com/showthread.php?t=1182065

    http://forums.macrumors.com/showthread.php?t=1105731

    http://forums.macrumors.com/showthread.php?t=1102894

    http://forums.macrumors.com/showthread.php?t=1195773
     

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