7 Replies Latest reply: Aug 24, 2010 6:58 AM by Scott Billings
Tomdm134 Level 1 Level 1 (0 points)
I have recently purchased my iMac around one month ago, this is the higher specced model with 2.66GHz Intel Core i5 (quad core). Ever since I have received my iMac I have been concerned about how hot it is getting, I not currently at my computer, but at standstill iStat Pro is saying around 35 centigrade, which is just warm to the touch at top of the back of the iMac, but when I start loading several programs at once, use large programs or run a game such as Warcraft, I get temperatures up to 50 centigrade and the top of the iMac is to hot to touch, allowing me to only touch it for a few seconds. The iMac reaches this temperature quite quickly and I am usually running it for 3-4 hour sessions at a time. Is this anything I should be concerned about? I thought I would post something on here before booking an appointment in the Apple store and having to go to trouble carrying it in. On a side note, I have been inside of the Apple store several times and asked someone about it, but they really didn't have much to say and just moved me along.

Thanks, Tom.

iMac 27", Mac OS X (10.6.4)
  • Fortuny Level 7 Level 7 (21,430 points)
    Hi Tom and welcome to Discussions,

    my 27" i7 iMac (specs below) is now up and running (doing this and that, nothing demanding) and I get the following temps with iStatpro (all in Celsius):

    HD - 50°
    CPU - 43°
    Ambient - 29°
    GPU Diode - 61°
    GPU Hetsink - 60°
    Mem.Controller - 52°
    Optical Drive - 49°
    Power Supply 2 - 58°

    The top of the iMac is hot to touch but bearable.

    Personally these temps don't give me any headache as they are well in a safe range.

    So have fun further on

  • Tomdm134 Level 1 Level 1 (0 points)
    Hi Fortuny,

    Thanks for the quick reply, once I had home, I will leave it running for a while and post the temperatures I am getting.
  • JaimieV Level 2 Level 2 (490 points)
    And for a second opinion, my i5 27" iMac runs like this (iStat nano):

    HD - 53'C
    CPU - 48'C
    Ambient - 24'C
    GPU Diode - 66'C
    GPU Heatsink - 66'C
    Mem Controller - 56'C
    Optical drive - 53'C

    These temps have caused the fans to ramp up a little from their base of 1100rpm to
    Optical 1350
    HD 1100
    CPU 1200

    Summertime, it's bad for computer temperatures!
    Likewise, hot to the touch but fine to hold.
  • WZZZ Level 6 Level 6 (12,775 points)
    You might want to install SMCFan Control, which will allow you to input different minimum fan settings. I have three such settings in increments, one for the hottest weather. When necessary -- it gets into the upper 90s here -- I ramp the fans up near to 2K. Apple likes quiet fans, which are a good selling point, but those quiet fans end up slow roasting the hardware. If it's hot to the touch, then that is much too hot. I also run a small, inexpensive fan near the back of the computer. When it gets very hot here, I allow the computer to sleep more often.

    I also can't think straight in weather like that, so I'm less likely to stay on the computer very long.


  • Ian R. Brown Level 6 Level 6 (18,580 points)
    I also have SMCFan Control installed . . . . it's free!

    However, I find that not only the weather but the actual programs in use have a dramatic effect.

    If I am just answering emails or surfing the web the iMac stays very cool, but open up any of the Final Cut Studio apps and I'm getting ready to call the fire brigade!

    The fans are supposed to speed up but I have never witnessed them doing this, so I use SMC to speed up the fans whenever I know I am going to be doing anything intensive.

    The highest temperature by far is always the Power Supply Position which at its hottest reaches 180˚F which I believe is over 80˚C.

    Message was edited by: Ian R. Brown
  • IMac temperature issue Level 1 Level 1 (0 points)
    Hi to everyone.
    I have a I7, that was originally an I5.
    It runs very hot:
    HD Imac 48
    CPU 50
    Ambient 27
    CPU Diode 66
    CPU Heatsink 60
    Mem Controller 53
    Optical Drive 49
    Power Supply 2 72
    I tried to install Fan control, but reads a temperature of -127, and after s wile running, sets the right fan to 4250 rpm.
    The back of the computer feels hot, but not much more than it was before the upgrade.
    Any suggestions?
  • Scott Billings Level 4 Level 4 (1,655 points)
    As an ACMT (Apple Certified Macintosh Technician) I wouldn't recommend that. Messing with the fans can create other problems you don't anticipate.

    Yes, Apple lets things run a little hot to keep fan noise down, but it's hardly the grand conspiracy you're trying to imply. They wouldn't let it get to the point where the system is going to damage itself, or they'd end up having to pay some significant out of pocket cash to fix everyone's systems. Companies like Apple exist to make money, pure and simple. Everything they do is designed around maximizing the money they make. All you have to do is take the final step of combining these two facts and spending about a half second reaching the pretty obvious conclusion.

    If indeed Apple was found to be intentionally running things at dangerous levels, you don't think there would be a class action lawsuit? That there aren't plenty of ambulance chaser lawyers out there who'd love to try and get a shot at Apple's deep pockets?

    It's time to take the tinfoil hat off. There's no great conspiracy here, and if you start messing with the speed of the fans, then among other things, you'll give a false positive reading if you ever need to run a diagnostic on the system. Without doing a SMC reset, the fan speeds will be out of whack, and the diagnostic program may error out (most stop checking when they find an error) before it gets to the real problem. So not only may you end up having someone replace a fan unnecessarily, but you wouldn't have actually solved the problem.

    The fans spin up as needed, and believe me, those fans can create a nice breeze when they're running full speed. You can feel it 2-3ft away if you don't have the display on the system. If things start getting too hot, the fans will kick it up a notch or two, and they can move some impressive amounts of air for their size.

    It also seems we need a refresher on high school level physics. Heat travels from hot to cold, seeking equilibrium. That is being some temperature between say ice and the liquid that makes up your drink. That means if something feels hot to the touch, it's because it is warmer than the surface of your hand, and your hand is absorbing heat energy. If something is cold to the touch, it means the object is absorbing heat energy from your hand. Every material also has a different thermal coefficient, or how much energy it takes to make it change 1 degree C up or down. Some substances, like water, have a very high number. Water can absorb massive quantities of heat.

    Moving along... There is actually an attachment (on the 27" models anyway) to the CPU heatsink that takes the form of a couple of heat pipes ending in a copper plate that is taped directly to the case of the new unibody iMacs, which is all 21.5" and 27" models. This allows the aluminum case of the iMac to function as a giant secondary heatsink. The fact that it feels warm to the touch means the case is doing what it is supposed to. Absorbing heat until it can be absorbed by the air.

    Aluminum has a very low number of the amount of energy it takes to raise it a single degree C. That means it takes on and releases heat energy very readily. Not as low as copper which is used for the direct contact parts, but good enough so that if you have the mass of the entire case to work with, it's fine.

    But the more readily something gives off heat energy, the hotter it will feel to the touch, even if it's not that hot. You can leave a pot of water on the stove for quite some time before it actually starts to feel hot if you put your finger into it, but the stove heating coils will feel hot almost instantly.

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