iMac 27" Aftermarket Cooling?

Discussion in 'iMac' started by D-Sider, Jan 14, 2010.

  1. D-Sider macrumors newbie

    Jan 14, 2010
    Hi all,

    I got myself one of the new i5 27" iMacs a few days ago. So far, I'm pretty impressed. I use OS X for everything other than gaming, and Windows 7 for the handful of games I play (COD:MW2, WoW, Unreal Tourament 3, Assassin's Creed etc) and the ATi 4850 has been able to run everything at native/highest resolution and on full quality settings.

    I have noticed though that the case gets ridiculously hot. I know they're designed for this, but are there aftermarket cooling solutions available? I'm assuming it would be something like a clip-on bar under the speakers with extra fans or something? Or am I just better off sticking a small desk fan behind the screen to cool down the back/heat sink?

    Also, is it normal for the CPU to idle with one core at 90-100% and the others at 20-30%? This happens in Windows 7, I haven't checked in OS X yet.

    Any help appreciated.
  2. miles01110 macrumors Core


    Jul 24, 2006
    The Ivory Tower (I'm not coming down)
    I doubt any aftermarket solution would be proportionately more effective than aiming a desk fan at the case.
  3. Eidorian macrumors Penryn


    Mar 23, 2005
    It is what it is. Apple is rather fond of lax fan speeds until you're nearing 100° C.
  4. D-Sider thread starter macrumors newbie

    Jan 14, 2010
    I figured as much. I'm relatively new to Mac hardware so I wasn't sure if there was a tried and tested solution.

    The good news is, during winter I won't need a heater. This thing pumps out more heat than the two PCs in the room combined, and they all have similar hardware specs.

    Thankfully I'm not quite there yet. Core temp is usually in the high 60s, haven't noticed it spill in to the 70s yet.

    I'm still a little concerned about the core utilisation though, hopefully it's fixed in a Windows 7 update.
  5. Eidorian macrumors Penryn


    Mar 23, 2005
    Get iStat Pro for OS X. You'll see the temperatures.
  6. gospel9 macrumors regular

    Sep 20, 2008
    I was just thinking about this the other day too. From my MBP experience the fans don't even try to really kick in until it is sitting around 78-80 Celcius. (fancontrol is a given).

    So there's nothing better than a crappy desk fan? (That's totally not going to work with me; I absolutely hate fans blowing near me, even in the summer).

    Not sure about Windows, in OS X 10.6 the cores are pretty much distributed uniformly on my previous i5.
  7. Eidorian macrumors Penryn


    Mar 23, 2005
    This is just from my experience but touch the top of your aluminium cased iMac. It gets rather hot too. What really bothers me is that the older plastic iMacs are cooler than the aluminium ones.
  8. Bryan Bowler macrumors 68040

    Sep 27, 2008
    #8 do realize that the aluminum should be hot, don't you? It's serving as a heat pulls the heat away from the components.

  9. rtrt macrumors 6502a

    Jan 19, 2008
    And the reverse is also true to an extent - have seen some very high temps on my imac g5 using i stat.

    Feel the case and it's warm - open the case and the part - disc drive in this case, is almost too hot to touch.

    Plastic case is insulating the internal components.

    Aluminium can only help imo but of course apple will just use this benefit to push the envelope further!
  10. Rodus macrumors 6502a


    Oct 25, 2008
    Midlands, UK
    SMC Fan Control is your friend here. My 4850 is overclocked to desktop speeds and doesn't get over 60 degrees c.
  11. AlaskaMoose macrumors 65816

    Apr 26, 2008
    Aluminum does cool faster than plastic and most other metals. That's why aluminum heat sinks are so common.

    Now, on my iMac G5, I purchased a very small computer cooling fan that is powered by a Radio Shack 6VDC transformer. I attached the fan right on the exhaust vent at the iMac's cover using dual-sided tape, and plugged the transformer to a switched extension cord. Whenever I hear the fans spinning fast, I turn the fan ON. Since the fan is so small, it does not interfere with the cooling process of the iMac, which by the way, gets hotter than my new iMac 21".
  12. Larpy macrumors member

    Jan 11, 2010
    I'm a little worried about heat as well as I live in a very hot and dusty place.

    Do you guys cover your imacs when they are not in use?

    also what temps are ok to continue to use the Imac at? I've just ordered an i7. any advice would be helpful.

  13. powerhouse7 macrumors regular

    Oct 21, 2009
    Canberra, Australia
    I've got the i7 and use smc fan control just to keep the temps a little lower for piece of mind. I'm not worried so much about the CPU but the GPU. my GPU was idling around 60-65 degrees Celsius (while that's not problematic) I installed SMC Fan Control to keep temps below 50 (the CPU idles at 40).

    Overclocking the GPU? Hmmmm.
  14. Giuly macrumors 68040


  15. Sun Baked macrumors G5

    Sun Baked

    May 19, 2002
    I thought the my old 2007 aluminum iMac got abnormally hot on top, to the human touch.

    Then I aimed a laser thermometer at it and it was only 107°F, it only felt hotter because aluminum is really good at transferring heat.

    One of the reasons we have all that anodized aluminum cookware.


    If you are worried, do what others say and bump the fan speeds up a notch. And don't go by touch, aim that laser pointer at the machine and read the actual temp of index finger's version of ridiculous.
  16. aki macrumors 6502a

    Mar 2, 2004
    There are lots of very informative threads on this topic. Here is my considered view for what it's worth.

    Firstly, yes iMacs do run on the hot side. They are pretty cramped (yes even the 27") and designed to be svelte. That has a cost.

    Second, yes they get hot to the touch. As posters have noted, this is most certainly by design. Touching your iMac tells you nothing except that the heat dissipation is working well. If you want to know what's going on inside, which is the point, use iStat or similar.

    Third, for normal use, the iMac does not require user intervention. This begs the question "What is normal use"? Here's my take. If you upgrade your hardware regularly, don't worry about temps. If you want or may want your iMac to last into the 3 to 5 year range, you should give it a thought. If you use your iMac mostly for email and websurfing and writing papers, forget about temps. If you do marathon gaming sessions, if you often game in bootcamp Windows, or if you do video processing or other "heavy lifting", you should give temps some thought.

    Fourth, most people who worry about temperatures worry about them needlessly; see point three above.

    Fifth, if you do use your iMac for heavy work or often use Windows and do want your machine to last a bit longer or at least know what's going on, the current prefered solution (imo) is iStat or Temperature Monitor or similar, which will give you temps in the menubar or in the Dashboard (OSX side only), and smcfancontrol, which will let you manually set minimum fan speeds (the setting can only be done from OSX, although you can have the fan speed settings carry over to a bootcamp Windows session provided you do a restart and don't switch off the iMac).

    Sixth, if you are setting fan speeds and looking at temps, what should you be looking for? The GPU and CPU are precious and expensive to replace obviously but they are also rated for quite high temperatures. The iMac is designed to shut itself down before you get to that point. What is rather more fragile is your internal HD. High temperatures don't kill HDs immediately, but they do reduce lifespan/increase failure rates. Of course you should be timemachining or similar anyway; but replacing a HD is tedious and stressful and can be very inconvenient. Again, having given due consideration to the points above, I think it's good to set speeds to keep your HD temps in the low 50s C. Under 50C is fine, over 55C is bad, in between is, well, reasonable given what the iMac is. (I should note when I talk about temperatures here I'm talking about high temperatures suistained over a period of time. Spikes in temperature, when you are transcoding a youtube clip or something, that's not worth being concerned about. I'm thinking here about all-night Crysis sessions or whatever.)

    Seventh, and final point. Environmental conditions play a role (more than I originally thought). Depending on where you live, ambient temperatures will have an effect - I'm in Japan and temps are clearly higher in summer than winter inside the iMac. Also, if you live in a dusty environment, it's not a waste of time to dust around your machine and desk regularly - your fans will suck up that dust over time.

    Eighth and actually final point. External fan solutions sound better than they may actually be. I'm not an engineer of any description, but I have read authoritative-sounding accounts of how the fans in the iMac are carefully and cunningly placed so as to maximize efficiency, by directing airflows from certain areas to other certain areas over so and so components. Which is to say, it's all a pretty neatly designed system. There used to be mods around where people would carve holes in the backs of their G5s (this is in the plastic era), and electrical-tape fans on there or what have you. Bad idea (generally speaking) - it just messes with the airflows that some team of very clever Apple engineers burnt countless nights laboring over. Or something. I'm being verbose, the point is, placing little desk fans at the base of your machine or pointing your fan at the air vent in the back might look like its helping - hey, it's cool air, right? - but it may or may not actually be that simple.

    Ok I'm done. Good luck! :)

    PS Ok I lied about being done - if you do elect to use smcfancontrol, it's generally better to trying uping all three fans a small amount than one fan a lot. Again, they are designed to work in concert.
  17. TMRaven macrumors 68020


    Nov 5, 2009
    I agree, external temps play a huge role in the cooling performance of the iMacs- which makes sense because their whole shell is a huge heatsink.

    At my apartment, where the temp is usually set to 78c, the average temperature of my cpu is 47-50c. At my dad's house, where the ac is a bigger unit and most of the cold air blasts my room, my iMac's cpu temperature is at around 39-42c doing the same thing (adium, iTunes, a couple flash programs)
  18. johnnymg macrumors 65816


    Nov 16, 2008
    78C in your apartment................. :eek: ................ :p
  19. TMRaven macrumors 68020


    Nov 5, 2009
    Oh. :p

    That's my habit of being used to using celcius for computer temps and fahrenheit for everything else, ha.

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