A7 in the iPad: more power, more savings

Going in to yesterday’s Apple Mac and iPad event, the expectation was that we would get new iPads. The good money was also that these new iPads would get new processors. The previous two generations of iPads had followed the introduction of new iPhones and had incorporated an upgraded version of that processor. But the new iPad Air and Retina iPad Mini? They both sport the A7 processor, the same chipset as in the month-old iPhone 5s.

The A7 in the iPhone 5s is a 64-bit 1.3GHz dual-core CPU coupled with what’s believed to be a PowerVR G6430 GPU. It has an advanced image signal processor, a “secure enclave” for storing and processing the Touch ID fingerprint sensor data, and offloads accelerometer, gyroscope, and compass motion-tracking to a dedicated low-power M7 coprocessor. The A7 is a powerful beast, but is it enough to handle an iPad?

A brief history of the A-series

The original iPad, launched in April 2010, was the first Apple device with a custom A-series processors, this one being the A4. The original A4 was an 800MHz ARM v7 Cortex-A8 single core chip with a PowerVR SGX 535 GPU. All that really means is that it was up to the task of pushing pixels around on that original iPad with its 1024x768 screen. It wasn’t the most powerful of chips, but considering that the original iPad was in a class all its own, that wasn’t an issue. By custom-designing their chipsets, Apple also was able to perform significant streamlining and optimizations that aren’t possible with off-the-shelf mobile processors from Samsung, Nvidia, and the like, giving the 800Mhz single core chip more power and efficiency than otherwise possible.

Two months later, Apple introduced the iPhone 4, using the same A4 chip as the iPad. Where the iPad display had 786,432 pixels, the new Retina display on the iPhone 4 clocked in a 640x960, good for 614,400 pixels, something the A4 was more than up to the task of handling.

In March 2011 the iPad 2 landed. The new iPad was thinner and lighter than the previous generation, and also had the new dual-core 1GHz A5 processor. Later in October, the iPhone 4S was announced, also with the A5 chipset, though clocked down to 800MHz for battery life reasons.

Things got interesting in March of 2012 with the introduction of the third generation "the new" iPad (which we’ll just call iPad 3 for sanity’s sake). Inside was an A5X processor, an improvement over the year-old A5. It still had two cores and was still clocked at 1GHz, but the GPU had seen a massive upgrade to a quad core unit, which Apple claimed had twice the graphics performance of the A5. Considering that the iPad 3 was also the first iPad with a Retina display, and thus had four times the pixels of the iPad 2, this extra power was desperately needed.

Six months later the iPhone 5 arrived with the A6 processor, a dual core 1.3GHz chip, which was upgraded to 1.4GHz in the A6X for the iPad 4 two months later in November (also the shortest turn-around time between iPad generations). Two generations in a row this set up the pattern: iPhone then iPad, A# then A#X. Or so we thought.

There are some aberrations in there, of course. The A5-powered iPad 2 continued to hang around in Apple’s line-up, discounted $100 to offer a less expensive alternative to those who didn’t want to spend $499 on the current-generation iPad, even if it was almost universally a markedly better product. The original iPad Mini, launched in November 2012 alongside the iPad 4, carried the same A5 chip as in the iPad 2, in many respects it was merely a smaller and less expensive version of the iPad 2.

In September of 2013 we were introduced to the iPhone 5s, which was powered by the new A7 processor. The A7 had two cores clocked at 1.3GHz, but added 64-bit processing to the mix based off the ARMv8 instruction set. The A7 was the most powerful A-series chip yet, and that came as no surprise. With the iPhone 5s launched in late September, conventional wisdom pegged November as the launch timeframe for an updated full-size iPad and iPad Mini, and conventional wisdom said that we should expect a new A7X processor for at least the big one.

But that’s not what happened. The A7 processor that’s in the iPhone 5 was announced to be powering the new iPad Air and iPad Mini. Surprise!

We've gone from the iPad processor being crammed into the iPhone, to the iPhone processor being upgraded for the iPad, to the iPhone processor just being dropped into the iPad.

Power enough to go around

The A5X and A6X existed because Apple knew that the A5 and A6 simply weren't up to the task of powering the Retina iPads.

Where the lower-resolution iPads had 786,432-pixel displays that the A4 and A5 could handle, the jump to Retina quadrupled that to 3,145,728 pixels. Technically the then-in-development A6 could have been dropped into the iPad 3 with that insane display, but the experience for the user would have been less than good.

Apple instead ramped up the power behind the A5 and gave us the A5X. When it came time for the fourth-generation iPad, Apple again cranked up the GHz on the previous iPhone processor and gave us the A6X.

If you just look at the specifications for the A7 on paper it doesn't seem that much more impressive than the A6. They both have two cores, both of which are clocked at 1.3Ghz. Where things go wildly different is with the application of 64-bit processing and a high-power quad-core GPU (previously only dual-core on the A5 and A5X).

That much horsepower makes for an iPhone 5s that screams. It's a fast phone and in a month's time there's been nary a report of lag of stutter or wondering if the processor can keep up, even with 727,040 pixels to push.

The Retina iPads, however, have more than four times as many pixels. Clearly Apple believes that the A7 can handle it well enough that there was no need to crank out an X variant this time. It's possible that there are some differences, maybe in clock speed or GPU configuration with the iPads' A7, but Apple gave no indication that there were changes. There weren't any impressive tech demos with gaming or rendering engines on stage to show off the A7 processor, because that's all stuff we've seen before.

Indeed, according to in-depth benchmarking tests done by the likes of AnandTech have shown that the A7 consistently outscores the A6X. If the A6X was good enough for the iPad 4, why wouldn't the more powerful and more modern A7 do the trick?

Based on hands-on reports from the launch event yesterday, the new iPads are tremendously responsive and fast, though those were just early impressions of a just-announced product. But so far it seems like the A7 from the iPhone is more than enough to power the iPad.

Scale and simplicity

Even if the A7 is powerful enough to power an iPad, using the same processor for multiple devices provides tremendous economies of scale for Apple. They can now get away with producing one processor to power the three most-modern devices in the iOS line-up.

The concept of economies of scale is relatively simple: the more you do of one thing, the easier and cheaper it is to do. It's why McDonald's can offer the Big Mac at as low of prices as they do and still turn a profit - they buy more beef than anybody and prepare it the same way around the globe. Mass purchasing and mass manufacturing help offset the single-time costs like the machines used to process all of those cows into 1.6oz hamburger patties by lowering the overall per-unit production cost. That same 1.6oz patty is used in six other McDonald's products for further cost benefits.

The same economies of scale that apply to McDonalds also apply to Apple. Producing the A6 and A6X processor was necessary, as the A6 just wouldn't cut it for the iPad. But it also meant having two separate manufacturing processes to build the different chips. It required more engineering effort to design two chips, duplicated quality assurance, and more.

The A5X and A6X were necessary, but they also complicated Apple's notoriously efficient manufacturing process.

Using the A7 in the three flagship products reduces that complexity. It's just one production process and one design. Making the A7 as powerful as it is probably means it was more expensive to design and produce than the A6. But it also only has to be designed once and then manufactured for years to come.

It frees up resources for Apple, allowing the design team to focus on their next project (presumably an A8 processor due out about a year from now) instead of wasting time building a step-up processor to bridge the gap.

The iPad Air and Retina iPad Mini running off the A7 aren't the only similarities the two new tablets have with the iPhone 5s. All three also contain 1GB of RAM, the M7 motion coprocessor, and front-facing 1.2MP FaceTime HD cameras.

Both the iPad Air and Retina iPad Mini have the same set of Bluetooth, Wi-Fi, and LTE radios, and the same 5.0MP rear camera. In fact, the only real difference between the two is their footprint, owing to the size of the screen, and the size of the battery needed to power the backlight for the screen.

The Retina iPad Mini has even more synergy happening with the iPhone - the 326PPI display on the new iPad Mini is the exact same pixel density as on the iPhone. The displays obviously aren't the same size, but the same manufacturing process that's been used to produce the 0.077mm-square pixels since the iPhone 4 came out can now be applied to the Retina iPad Mini.

It's the reason the iPad Mini has exactly a 7.85-inch display, so when they went Retina with it they could exercise some additional economies of scale. More tiny pixels for everyone.

Using the same parts across the entire iOS line-up like this reduces the acquisition and production costs for Apple. It makes manufacturing easier, and frees up precious human resources to focus on other challenges.

Where we stand today is with the A7 in the iPhone 5s, iPad Air, and Retina iPad Mini. The A6 exists only in the iPhone 5c. The A5 is still a surprisingly well-used processor, finding a home in the iPhone 4S, iPad 2, first generation iPad Mini, the iPod Touch, and the Apple TV. And there's still the A4 in the iPhone 4 being sold in less-wealthy markets around the globe, though we can't imagine that the A4 production line is very large (if even active - for all we know Apple's just working through a stockpile of the processors).

What's next for the A-series?

It's hard to prognosticate what exactly Apple is going to do, apart from release new products eventually (unless your name is iPod Classic). As it currently stands, running four (or three?) processor production lines isn’t the worst thing Apple could be doing.

Apple broke what was assumed to be the beginning of a pattern (two instances does not a pattern make, as they say) with the introduction of the A7 and the use of it seemingly unaltered in the new iPads. Hypothetically-speaking, an A8 processor that's even more powerful than the A7 would be more than enough for both a new iPhone and a new iPad.

Is this the beginning of a new pattern? Will we see Apple continue to simplify their product line to the point that the only difference between an iPhone, an iPad Air, and an iPad Mini is the size of the display and battery? Economies of scale say that would be a good idea.

We saw with the introduction of the updated MacBook Pro laptops that Apple was able to lop $200 off the price while dropping in faster processors, RAM, and flash storage. Much of the cost of the laptop was associated with that storage and the pixel-happy Retina displays above them, unprecedented in a consumer device at launch.

But since ramping up production with the Retina-screened 15-inch MacBook Pro and then the 13-inch version, Apple's been able to decrease their per-unit costs enough that they could also reduce the price to consumers. Make the computer better but yet less expensive means more people can buy it, which means Apple can make more and further reduce per-unit costs. Which will make investors happy, because that means more of the all-driving profit.

It's likely we'll see the simultaneous three (or four?) A-series processor lines continue for at least the next few years. The same economies of scale that apply over mass manufacturer also apply over time - the A6 is cheaper to produce today than it was a year ago, so Apple can offer the iPhone 5c at a lower price than the iPhone 5 was at launch.

The A5 has proven to be a versatile chip, powering everything from the iPhone 4S and iPad 2 to the 1080p Apple TV. Is the A7 up to the task of powering the 8,553,600 pixels that you'll find in a UHD/4K television? That's nearly three times as many pixels as you'll find in a Retina iPad, so maybe we'll have to wait for an A8 chip for that mythological 4K Apple TV set.

Or maybe an A8X would do the trick...

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