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iMic
1st September 2012, 04:03 PM
I recently purchased a MacBook Air (Mid 2012) Configure-To-Order with an Intel Core i5-3427U Processor (1.80GHz), 8GB Memory and 512GB Solid State Drive. I'll begin by saying the combination of mobility and performance makes this the single best computer I've ever owned. The enclosure design, mechanical component design and reduced number of parts required also make this an ideal machine for someone like me (I'm an Apple Technician, the fewer parts and failure points, the better). I could not be happier.

What has me curious is that this machine has been able to reach CPU temperatures of 107C before, primarily under heavy combined graphics and processor utilisation. Normally one wouldn't be concerned about this, the hardware is designed to throttle and shut itself down to prevent damage if the specifications are exceeded.

Now, Intel's "TJunction Max" temperature (http://ark.intel.com/products/64903/Intel-Core-i5-3427U-Processor-(3M-Cache-up-to-2_80-GHz)) for this model is 105C. The MacBook Air is exceeding it ever so slightly, and isn't throttling back as the temperature remains consistent. Perhaps the onboard monitors are determining that the computer can handle the situation and is allowing this accordingly (as Intel's Turbo Boost feature is designed to do).

In addition, the drop across the heatsink seems abnormally large. When the computer was operating at 105C at the processor die, the heatsink was reporting a temperature of only 50C, or less than half of the heat at the processor. Even now, at 50C at the core, only 34C is being reported at the heatsink. These temperatures are being reported by iStat Menus 3. I'm not sure if the temperatures are estimates however as I don't believe the MacBook Air heatsink actually contains any electronic temperature sensors, it appears to be a pretty basic pipe and fin-stack arrangement when removed from the system.

I don't have any reason to believe that this will result in any damage. I do reduce the utilisation of the system when it crosses the 95C marker however as longevity of this system is a primary concern, as is the case with most machines I own (I usually service them, change thermal paste, clean fin stacks and adjust trackpads among other things at scheduled regular service intervals and as needed, so you could say I'm a little obsessive, but the condition of these machines make it all worth it).

Does anyone else have a MacBook Air and find themselves crossing into the higher temperatures frequently? If we also have some hardware engineers or experts in this field I would also be interested to hear your input on this. Apple has no documentation about the thermal system of its products, so it's dependent on real-world usage scenarios to piece together the details in these cases.

Cheers,

Mic.

nibbles
1st September 2012, 04:51 PM
I find mine runs hot (>95˚) occasionally when running things like VMWare Fusion, or debugging apps that have huge cpu issues, the other killer is Flash but I try to avoid that as much as possible.

Usually when I reach these temps I ensure there is adequate airflow around the vents, i.e if it's on my lap i'll make sure to put it on a solid surface, and then look to see what apps are causing it and try and remove the cause of it.

I haven't looked at the temp on the heat-sink, I normally use the iStat widget on the summary but next time it happens i'll have a look at the temperatures in other areas.

nibbles
2nd September 2012, 09:12 AM
Just had mine heat up using Google Sketchup - Layout and trying to render a complex drawing. Got a screenshot of the temps:

http://oi47.tinypic.com/34e2h6s.jpg