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Aluminium iMacs – Heat Issue

The Set Up

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In our studio we have a mix of iMacs (G5, Intel), Mac Minis (Intel) and Mac Pros. We run 10.5 and 10.6 along with Adobe CS3 or CS5 on them.


What we found is, that amongst these machines, Intel aluminium iMacs are the least durable of the lot.


Those being older than two years are prone to freeze up, show graphic glitches or the optical drives work very unreliable.


We gave some of these machines to a qualified repair shop, but they were not able to reproduce the problems we experienced.



Finding The Problem

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While trying to get to the bottom of these issues I discovered smcFanControl which let's you monitor the temperature of internal components and adjust the respective cooling fans.


I installed it on nine machines and here is what I found.


A new iMac (i5, 27", less than 1 year) shows normal hard drive temperatures at around 30 - 35Cº.


Older machines (CoreDuo, Core2Duos, i7) were running their hard drives at around 45-50Cº (idle).


Those machines causing problems showed hard drive temperatures of 50 to 55 Cº in idle state.


Western Digital does not recommend to run its drives above 50C. Seagate does not recommend temperatures above 60Cº. In general it is assumed that a healthy working temperature for hard drives lies between 35 - 45Cº.


Please note, I was conducting these measurements in November.


My two year old 27" i7 has a problem with Spotlight, whose index seems to get corrupted frequently. Rebuilding the index every couple of month helps but the problem keeps coming back. During an export in After Effects I observed temperatures of up to 68Cº! In idle state I'm getting 45-50Cº.


Looking at the issues again – graphic glitches, non working or unreliable optical drives, slow or unstable performance – it all starts to make sense now.



Preliminary Conclusion

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The cooling layout in these slick machines is anything but robust. What I assume is, that over time you can expect dust to build up internally, blocking the ventilation and thus causing temperature hot spots.


What surprises me is, that OSX 10.6 (retail) does not seem to see the need of turning up the cooling fans even when a hard drive runs near it's terminal operating temperature.



Further Steps

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I will go ahead and give some of these machines an internal clean up. I might just as well give it a go and replace some of the battered hard drives with SSD's instead and see if this helps to keep temperatures in check.


I will let you know about my findings. I found so much useful help in this forum – was about time to give something back.

iMac, Mac OS X (10.6.8), graphic design, professional use

Posted on Dec 3, 2011 1:21 PM

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Aluminium iMacs – Heat Issue

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