It's been typical all along that Apple was downclocking the SOC for the iPhone, to extend life a little with a smaller battery. That's not really news. And you can well expect that for some things, like video decoding, pretty much the same AVC decoders are keeping the CPU out of the equation. Apple previously also doubled-down on GPUs for the tablet over the phone, this is the first time they haven't.
But of course, iPhones and iPads are designed for the same battery life target every time, and the battery scaled accordingly. If you look at the history of iPad batteries, it was the addition of the high density display ("Retina" in Applespeak) that caused a big bump in battery power, from 25Whr in the iPad 2 to up to 43Whr in the iPad 3. That was needed, as display, not the SOC, had already been the main source of power drain, and that new display at the time took about twice the LED power to deliver the same brightness.
So now they're down to a smaller 33Whr cell, claiming all the same expected runtimes as usual, and Apple's generally been on target with their claims. I'd say that pretty much confirms they're using an IZGO LCD, rather than the classic IPS. These claim to transmit far more light even at the higher pixel densities. And Amazon is already shipping with technology.. it also leads to thinner displays.
- surfing the web (=mostly idle CPU, no GPU + active display),
- watching video (hard IP for video decoding => CPU & GPU idle),
- listening to music (CPU & GPU idle, no screen... ONLY 10 HOURS????)
So, how much battery life while using the additional CPU & GPU power of the A7?
Tablets and smartphones are becoming a gaming plateform. It's high time the tablets & smartphone vendors start publishing battery life figures on gaming workloads. (or simply displaying the power consumption of their systems during each CPU and GPU benchmark these guys use to sell the processing power of their devices)
It is quite an accomplishment to achieve a thinner iPad. Even performance stayed the same with just reduce the size of battery, the task wouldn't be easy. Now, the processor runs faster. Application performance will be improved. The rest of the features will likely be apps driven. Bluetooth 4.0 will be the focus of a lot of developers and company building ioT. iBeacon will no doubt open up a lot of opportunities. The near future will tell. :)
Apple, like many large companies has a "no talk" policy about which EDA tools they use, and their general methodology, because they consider this a competitive advantage. Why let your competitor's know how to catch up to you?
Apple has wonderful designers and design tools. The way they convert power with ultra high efficiency and manage very low thermal, is wonderful achievement. This is true for iphone, ipad and mac books. It will be good to know what kind of design tools and design process they employ. Can any Apple veteran highlight these tools and processes?
Tom at Chipworks speculated the heat sink was because Apple was cranking up the frequency on the A7 to 1.4 GHz so it is running warmer in the bigger tablet.
FYI, I think the POP that Chipmonk mentioned was a memory stack, separate from the A7. It would be interesting to get a teardown of any POP mempory stack in the iPad Air and comparisons of prior memory stacks Apple used.
Addendum : in theory the larger screens in Tablets compared to SmartPhones would require the GPUs to work harder, making the SoC run hotter. But would still like to understand the difference in Packaging used by Tablet mfr.s no. 1 and 2. Perhaps have to wait till the next Tablet by no. 2. They keep using ARM Mali GPUs. Or does Android in some way have less power hungry graphics ?