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Jul 11, 2015, 10:25 AM
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IOS Devices and Pilot App Thermal Throttling.


Hi Folks, a big one this, iv been looking specifically into Apples devices supported by the Pilot app and thermal throttling and shutdown, i wanted to look into some of the possible reasons and ways around it, looking into it i have found a few conclusions,

First of all looking at Apple A7 devices, the Mini 2/3 iPhone 5S and the Air 1st gen.

Looking at the design both are similar with the batteries located next to the logic board, The SOC on both is located under a metal EMF shielding, this does not seem to offer any substantial heat dissipation, no thermal compound is used and it does not make contact with the SOC directly.

The interesting thing is all of the packages on the logic board are located facing up towards the screen, This means Apple are not making use of the Aluminium shell as part of a heat sink, the second thing with this is heat from the display is also reflected back towards the processors as well.

Ipad Mini


https://d3nevzfk7ii3be.cloudfront.net/igi/OaqPYROb6isFW4oP][/URL]

Ipad Air


https://d3nevzfk7ii3be.cloudfront.net/igi/tVQvayERBfCgAUcC.huge][/URL]

The A7 SOC , there are 2 versions of this SOC, a different chip in the Air than in the Mini 2/3 iPhone 5S. Its a Duel Core clocked at 1.3ghz in the Mini2/3/5S and 1.4Ghz in the Air.

The A7 in the Mini is a POP setup with the 1GB of ram stacked on top of the core as part of the chip, this is one unit with no metal heat spreader on top.



https://upload.wikimedia.org/wikipedia/commons/7/7f/Apple_A7_chip.jpg][/URL]




The A7 in the Air is a different setup and uses a Chip on Board method, this means the A7 and the ram are separate components, they are then both located on a board with with metal heat spreader covering both making a singular chip again.



https://upload.wikimedia.org/wikipedia/commons/a/ad/Apple_A7_S5L9865_chip.jpg][/URL]



Lastly on the A7, CPU throttling, its been noticed by several benchmarks the the A7 throttles CPU speed very aggressively, the one in the Mini especially, this one drops speed after 2 minutes from 1300mhz down to 900mhz-1000 mhz where are the A7 in the Air has a far more gradual throttle curve.


Note the iPhone 5S is the same as the Mini 2/3
http://images.anandtech.com/reviews/tablets/apple/ipadair/throttle.png][/URL]



Based on the information above the Air should perform better in hotter conditions than the Mini2/3/

iPhone 6 & Plus

This is of Apples standard design again with battery to the side of the logic board and the SOC located under EMC shielding facing the screen



https://d3nevzfk7ii3be.cloudfront.net/igi/6MaZk5cEE2tm1uCj.huge][/URL]




The A8


https://upload.wikimedia.org/wikipedia/commons/a/a9/Apple_A8_system-on-a-chip.jpg][/URL]



This SOC uses the new 20nm process,Again duel core but clocked at 1.5ghz this is based again on the POP setup with 1GB of ram onboard.

CPU throttling is less aggressive on the A8 although it does still drop quite quickly, after a few minutes its dropped to 1300mhz , after 10 minutes its got down to around 1100mhz, its been noted the iPhone 6 holds up a bit better than the 6 Plus in this respect even though its the same SOC.



http://cdn.arstechnica.net/wp-content/uploads/2014/09/iPhone-6-charts.015.png][/URL]



By 20 minutes huge drops in speed can be seen


http://cdn.arstechnica.net/wp-content/uploads/2014/09/iPhone-6-charts.016.png][/URL]




The iPad Air 2.
Again same design as previous models.




https://d3nevzfk7ii3be.cloudfront.net/igi/NeGiCOhnBaNRXUqx.huge][/URL]



The A8X



https://upload.wikimedia.org/wikipedia/commons/7/72/Apple_A8X_system-on-a-chip.jpg][/URL]




The A8X is a triple core SOC clocked at 1.5ghz, and 2 GB of ram, its also fitted with a more powerful GPU compares to the A8, its not a POP package with the ram being a separate chip like previous X models of Apples A series, just like the others its fitted with a metal heat spreader again.

There is currently no throttling data for the A8X unfortunately.


Final Conclusion,

Based on the information the Ipad Air and Air 2 should give best performance in hotter conditions,CPU throttling takes longer to kick in and is far less aggressive on these models, the Air 2 especially should be the best with extra ram and one extra CPU core, there is huge room for improvement in thermal design in tablets, most are designed to be used indoors and it seems manufactures are ignoring this particular area for improvement.

From our point of view there are a few things we can do to help the situation, make sure the device is not in a case, keep it out of direct sunlight by using a shade, cool it before use, these are about the limit to what we can do in the field.

Hope this help.

Links

DJI Store http://click.dji.com/ewNB7_KlfI1ctZ3U

DJI Phantom 4 http://click.dji.com/ewNB7_KlW2SdbyRy?pm=link&as=0001

DJI Phantom 3 http://click.dji.com/ewNB7_KlntMl6jMw?pm=link&as=0001

DJI Inspire 1 http://click.dji.com/ewNB7_KlixhKtwvR?pm=link&as=0001

Please Note: As with all my own blog post all links may be affiliate links and i may receive a small commission on any purchase bought through them , if you wish to support me then then are there otherwise you can navigate directly to DJI's website, thank you.
Last edited by Mad_angler1; Apr 02, 2016 at 04:33 PM.
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