External monitor = increased heat?

Discussion in 'MacBook Pro' started by rainydays, May 20, 2007.

  1. rainydays macrumors 6502a

    Nov 6, 2006
    A couple of weeks ago I bought a 22" widescreen LCD for my Macbook. This setup works great except for one thing. I get a temperature increase by 15-20C.

    When using it without the external screen the idle temperature is around 40-45C with a fan speed of about 1800-2000rpm when I plug in the monitor it goes up to 60-65C and a fan speed of 4500-5200rpm.

    Under just a little load 20-30% the temperature goes up a lot and the fan start spinning full speed. Which is usually only a problem when I do really CPU-intensive tasks with only the Macbook screen.

    Is this normal? Is it the GPU that heats up a lot when using an external monitor? I can't believe this is how it's supposed to be.

    I was planning on buying an iMac first, but people here convinced me that since I was pleased with the MB, buying an external screen for it would be just as good.
    But this is hard to live with actually. I'm very sensitive to fan noise and the small notebook fan is really loud when it's spinning full speed.
    Also, when producing music the fan cuts through the music (even when playing fairly loud) and makes it hard to concentrate on the sound when mixing.
    And recording in the same room is out of the question with the external screen connected.

    So is this normal? If it is, do you know any solution to it?
    I've considered getting a cooling pad, but I'm just not sure if it will help at all.

    Since I bought the screen I can't afford an iMac right now. And it seems to be a bad time for buying one anyway.
  2. scottlinux macrumors 6502a


    Sep 21, 2005
    When when running an additional display, more work is put on the GPU. This is normal, esp with large external displays that take a lot of punch to run.
  3. rainydays thread starter macrumors 6502a

    Nov 6, 2006
    I understand that the GPU has to work harder. But frankly, I don't understand how it can make that big difference regarding the CPU temperature.
  4. DrBunsenHoneyde macrumors member

    Sep 27, 2006
    Actually i am quite intrested in this cus I am about to buy a 22" widescreen to wall mount above where I put the laptop usually, intresting to find out if this is the norm.....
  5. localoid macrumors 68020


    Feb 20, 2007
    America's Third World
    Are both displays active when this temp increase occurs, or is just the external display active?
  6. chex macrumors regular

    May 17, 2007
    assuming the cpu and gpu are hooked up to the same heatsink (which is common in many laptops) its possible that the readings you get in istat for a laptop are not 100% accurate and are biased upwards by the extra load on the gpu.
  7. rainydays thread starter macrumors 6502a

    Nov 6, 2006
    Can't believe I didn't think of this before. But it seems like the combination of the external display and my firewire audio interface is making it super hot.

    I didn't realize this since I has no problem with only having the firewire audio interface connected. The temperatures were normal then (at least not much different).
    I tried unplugging it, and now the temperature reads about the same, but the fan speed went down a lot, to an acceptable level actually. Which would mean that it runs a bit cooler now.

    I'm still not sure why my audio interface is making it run so hot. Perhaps it's running on bus power even though the power adapter is connected? Would it be worth buying an 4to6 pin converter for my 4 pin firewire cable just to make sure it's not on bus power?
    Or is it the constant stream of audio data through the firewire port that is making it run so hot?

    Anyone have any experience with this?
  8. rainydays thread starter macrumors 6502a

    Nov 6, 2006
    Actually, to my surprise. It seems to run a bit cooler when both displays are active. :confused:
  9. DrBunsenHoneyde macrumors member

    Sep 27, 2006
    oh good :) will order my monitor in the next few days then hehe :)
  10. pip11 macrumors member

    Apr 29, 2005
    I use my 20" Dell occasionally with my MB CD (through DVI), and it does run noticably hotter when I use the external display in clamshell (so the screen is closed). With both displays active though, the fan seems to stay at the same 1500rpm that it always does.

    I assume that the fan controller is more zealous when it knows that the screen is closed, so the fan speed will increase much faster than usual. The lag between CPU load and the fan ramp-up always seemed bizarre under normal use: like if I start compiling something, the fan will start roaring, but only after a minute or two. Sometimes I don't even hear it until the compile is already done.
  11. imMAColata macrumors member

    Sep 26, 2006
    Is the lid close when the machine runs most hot? IS the lid open when the machine runs least hot? That could very well be the difference. With closed lid you have less efficient airflow in the macbook - perhaps.
  12. rainydays thread starter macrumors 6502a

    Nov 6, 2006
    Yes the lid is open always, even when the main screen is off. I don't trust it running with the lid closed, since the airflow seems to be pretty bad in that mode.
  13. scottlinux macrumors 6502a


    Sep 21, 2005
    Yeah FW audio devices pull a lot of juice with notebooks.

    There are things called a 'USB notebook cooler' for as little as $20 or so that is basically a set of fans that are underneath the notebook. Lots of people have great success with something like this. Though you would probably have to shop around to make sure and find one that is silent.
  14. rainydays thread starter macrumors 6502a

    Nov 6, 2006
    Hm, not notebooks in general, but notebooks with OS X, ehm yeah, macbooks.

    I did some more research and found that the firewire audio driver in OS X is the cause. It creates nasty CPU spikes which causes the temperature to raise and also makes audio recording less reliable.

    Also, it seems like Apple has known about this for ages but has done nothing about it. It's said to be included in Leopard, but that won't be released until October IIRC. That's a long time. And it's not going to be fun working with audio on the Macbook with this problem.

    And most midrange firewire audio interfaces use BeBob nowdays, which means that using the MacOS X driver is pretty much the only option even if I switch to another audio interface.


    Shouldn't these things be a high priority for a company that even makes a DAW application?
  15. scottlinux macrumors 6502a


    Sep 21, 2005
    I don't think this is entirely the case. What is your source on that? Many audio professionals (me included) and studios around the world use OS X with firewire audio devices. Ex: Digidesign devices.

    Some of the high end audio devices for OS X are firewire:


    What is your device that is giving you problems?

    M-Audio FW410 is not a bebob device. There are others...
  16. rainydays thread starter macrumors 6502a

    Nov 6, 2006
    My source? An email from Presonus confirming the issue. A lot of posts in several forums (bigblue, apple etc.) where people with different audio interfaces (presonus, focusrite, edirol etc.) are complaining about the same thing.

    Seems like the only ones not affected are the ones that use interfaces with third party drivers.

    If I connect the Firebox to my linux laptop it doesn't use much CPU at all, and that laptop is much weaker. And I've connected it to lots of other computers (windows and linux), never seen that problem. So the issue is very likely to be the apple firewire audio driver. Not very surprising since a lot of users report the same thing.

    I hope that the fix is included in the 10.4.10 update. But it doesn't seem very likely.
  17. scottlinux macrumors 6502a


    Sep 21, 2005
    Yeouch okay that's too bad. Well other than getting onto the Presonus folks, you might have to find another device. Ok good luck. Thanks for the heads up.
  18. acidbahia macrumors newbie

    Aug 20, 2008

    I have the same exact problem..did you find any solution by any chance?
    Have a good day.
  19. cluthz macrumors 68040


    Jun 15, 2004
    On my MPB its actually not much difference between running two screen or just one.

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