12 Replies Latest reply: Sep 13, 2009 5:34 PM by iyacyas
Schrodinger56 Level 1 (30 points)
I have an iMac 3.06Ghz Intel Core 2 Duo 24" and notice that the top of the casing gets pretty hot after a few hours of use, is this normal? I'm not playing any games or anything like that just browsing and using the odd application like Pages or iTunes.


iMac 3.06Ghz Intel Core 2 Duo, Mac OS X (10.6)
  • iyacyas Level 4 (1,535 points)
    It is normal for the top to get warm as this is where the heat vents from the machine.

    Now the word hot is up for interpretation. If the iMac is hot to where one can not stand to touch it then I would say that it is to hot.

    The best solution would be to download iStat. This will tell you all the temps of your Mac and the Speeds of fans. There are a lot of other good data that is reported by iStat that you may find handy.

    Get this app, check the temps then post back with the results.
  • sekitori25 Level 1 (0 points)
    The top of my Intel iMac can feel quite hot, but never to the point that I can't stand to touch it. The techs at Apple have told me that computers such as mine can run very, very warm and if the temperature reaches an abnormally high level, they will shut down before any damage can occur.

    While iStat pro can provide valuable information concerning temperatures, fan speeds, and other things, I only use it occasionally and just for reference. I find no reason for continually checking it out while the computer is running well. The hottest individual temperature listed on my iStat, by several degrees, is the GPU Diode. It can reach the low to mid 150° F level (about 68° C) depending on the period of time I've used the computer and what I'm using it for. Realizing that something in your computer is operating at around 70% of the boiling point, while being perfectly normal, can still be alarming. That fact can cause people to constantly monitor those temps "just in case". Doing that can become very distracting, especially since such monitoring isn't necessary. Actually, when the temps reach such high levels, they always drop back a few degrees. The system controlling the temperatures seems to work very well.

    As the experts have said, if the computer functions normally in all respects, how hot it may feel or the temperatures indicated don't really matter very much. I guess I could install smcFanControl to increase the fan speeds and I assume that probably would lower the temperatures a little. But since my computer continues to perform well using its factory default fan speeds and has never shut down because of heat related problems, I don't see the need for doing that.
  • iyacyas Level 4 (1,535 points)
    The suggestion of running iStat was not intended to be for longterm use. It's simply a method to check, if you suspect a problem. Electronics especially computers run hot and yes the inside of your CPU can easily pass boiling temp, it's performing 3 billion calculations per second!

    Loading smcFanControl is not necessary unless your machine is for some reason running hotter that normal, in which yours is not. If your iMac was getting to say 170 to 180 deg (F) on a continual bases then I would say that would be abnormal.
  • Schrodinger56 Level 1 (30 points)
    Out of interest I installed iStat to see what the temperatures were.

    What's a Northbridge temperature ?

    The values were but not sure if in degC or degF:-

    Ambient 24
    CPU 44
    CPU Heatsink 41
    GPU Diode 50
    GPU Heatsink 48
    HD Bay 48
    Mem Controller 45
    Northbridge 69
    Northbridge 53
    Optical Drive 42
    Power Supply 60

    CPU 1200rpm (variable)
    Hard Drive 1567rpm
    Optical Drive 798rpm

    Do the above figure seem reasonable?

  • iyacyas Level 4 (1,535 points)
    The temps you listed are in Celsius and appear normal, the only one that looks a little iffy is the Northbridge temp. It reads 156 degrees (F) but it still does not seem unsafe.

    The Northbridge is the Chip on the board that controls read and write to and from memory.
  • Schrodinger56 Level 1 (30 points)
    Would it be reasonable then to conclude that the position of this Nothbridge chip is somewhere near the top left (as you look at it from the front) of the machine because that's where the hottest part is?
  • iyacyas Level 4 (1,535 points)
    Not sure where the Northbridge is located, but I believe the heat sinks for the GPU/CPU are located on the left side middle of the iMac and there is a fan located directly below it. The fan blows are up and over the vents to cool them and the hot air then escapes the top left of the iMac. I also believe that the Power Supply is located top left of the iMac.
  • Xian Rinpoche Level 1 (140 points)
    The power supply on the iMac is located near the top left corner. The GPU is located a bit below. Heat from the GPU is blown off by a fan and travels right across the power supply on its way out. As a result, the power supply not only generates its own heat, but has the heat from cooled GPU added. The top left can get extremely hot (enough to approach "painful"). I consider this to be a design flaw, but Apple obviously won't redesign iMacs already sold. There are many, many options, but for my dollar, I've decided to just invest in Applecare. I had a HDD failure recently and (tremendously inflated) repair price was $300+, thankfully under warranty. Something tells me that with heat output like this, my iMac is going to be in for repairs several times. The Applecare warranty on Amazon isn't terribly expensive, so I' gonna go with peace of mind (and an external HDD running Time Machine ).
  • Apple4Ever556 Level 1 (30 points)
    where is there a link for iStat
  • sekitori25 Level 1 (0 points)
    where is there a link for iStat

    Type "iStat pro" in the search box at the top of the page and click on it.
    You'll see a link called Apple - Downloads - Dashboard Widgets - iStat pro.
    Selecting it will take you to a site where you can get some information about iStat pro. You can also download it there.
  • Onio-n Level 1 (50 points)
    Northbridge is the GPU in the most recent iMacs. (I'm saying that as the new iMacs say no temp for the GPU anymore so I guess that must be it) If Northbridge is the GPU then it would be on the motherboard(logicboard) near the bottom of the iMac.
  • iyacyas Level 4 (1,535 points)