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When looking at cases designed around the Intel NUC Atom-based board it seems they put a lot of effort into thermal dissipation (i.e. the entire case is basically a big heatsink). Of course, these cases are fanless and the logic goes that since there is no fan you need to get rid of heat by some other means - hence the huge heatsink.

However, my smartphone contains a very comparable processor (Qualcomm Snapdragon) and my phone contains neither a fan nor that huge heatsink. The TDP for the Intel Atom is advertised as 5W whereas it seems the Snapdragon is closer to 2.5W .

My questions are:

  • Is the Snapdragon's thermal design just so vastly superior to that of the Intel Atom processor or is there some benefit to the Intel Atom that I'm missing?
  • Also, assuming that the 5W/2.5W numbers are accurate, does that justify the huge difference between cooling solutions?
  • Are there any other solutions (for running a linux-based appliance) that I should look at that have solid industrial support but neither require a huge heatsink nor a fan?
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  • \$\begingroup\$ What frequency are they clocked at? \$\endgroup\$ – AlanZ2223 Feb 4 '15 at 21:39
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    \$\begingroup\$ The Atom is around 1.5GHz whereas the Snapdragon runs at about 2.5GHz. This is probably the max clock speed so I'm assuming those processors are running at a slower clock most of the time. \$\endgroup\$ – gardarh Feb 4 '15 at 21:46
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    \$\begingroup\$ In the title, you say "similar ARM processors"; but the Intel Atom is not an ARM architecture but rather x64-86 so you're comparing apples and oranges. \$\endgroup\$ – tcrosley Feb 4 '15 at 22:28
  • \$\begingroup\$ What I mean is that the processors have similar capabilities even though they run on different architectures. Paraphrasing the question: Why does running bare boned linux require so vastly different thermal solutions for these two different types of processors? \$\endgroup\$ – gardarh Feb 4 '15 at 22:42
  • \$\begingroup\$ TDP follows the intended platform. The E3xxx Atoms are for embedded systems and thin clients. Z3xxx Atoms are what Intel has to compete with the Snapdragon line. \$\endgroup\$ – mng Feb 5 '15 at 0:03
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The atom processor is based on an older architecture, plus it has to carry the baggage of being PC-compatible. So it is more complicated to implement therefore requiring significantly more transistors for similar capabilities. I believe the term RISC came after the x86 was well on its way.

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I would like to try to answer why one might want to add extra cooling, although I can't answer why it was done in this case.

For CMOS, from a low power design perspective, a lower temperature means several things:lower leakage and higher maximum speed. The maximum speed improvement allows you to reduce the supply voltage which further improves both leakage and active power.

A bigger heatsink may also mean that you can do away with the fan. Fans are often the cause of early failure.

Additionally, a lower temperature means longer lifetime. And NBTI which I won't go into details about, is also temperature dependent.

Summing up, adding extra cooling to a design means a potential improved quality.

However, you can't compare the quality of two designs by the size of their heat sinks!

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