Apple's A7 processor chip was a breakthrough in processing power for mobile devices. The A7 was the first ever smartphone CPU to offer dazzling 64-bit performance, and still economical enough to offer all-day battery. The Apple A7 is undeniably powerful - but the question is why.
In this feature, we're going to take a look inside the Apple A7 and see why Apple produced a chip so much more powerful than its rivals. We also look at what Apple has planned for its processors in the future.
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What is the Apple A7?
The Apple A7 is a System on Chip (SoC) that sits at the heart of the iPhone 5s, iPad Air and the iPad mini (second generation). The A7 is the chipset that controls all the other components in the iPhone (such as the display and storage).
The iPhone 5s was the first ever smartphone to ship with a 64-bit processor, and Apple claimed that the A7 chip offers desktop-class computing. Recent analysis has shown that this is not an idle claim; the A7 is a thoroughbred amongst chipsets.
The Apple A7 is not a chip as such, but a System on Chip (SoC) that combines multiple components into a single chip. Think of it as the insides of a computer (processor, graphics card, sensors) miniaturised into a single component.
See also: iFixit’s Apple A7 teardown
The Apple A7 processor and chip specs
At the heart of the Apple A7 sits an ARM processor nicknamed "Cyclone". Cyclone is officially a dual-core ARMv8-A processor running at 1.3-1.4GHz.
The other half of the Apple A7 processor is also a GPU (graphics processing unit) which is believed to be a PowerVR G6430.
Apple was first to introduce the ARMv8-A to a smartphone, and it's a doozy. Other smartphones may run at faster clock speeds, but Apple's A7 is a much more capable chipset - it performs more calculations simultaneously (and because the A7 is running at a more efficient clock speed it has better battery life and lower heat, which is why the iPhone is thinner than other phones)
There is a considerable amount of cached memory in the Apple A7, again matching desktop levels. Cached memory is another feature that speeds up the operation of Apple devices.
The Apple A7 has L1 cache of 64GK for data and 64 KB for instructions, and a L2 cache of 1 MB shared across the two CPU cores. It also has a 4 MB L3 cache that works across the entire SoC. Cached memory is additional memory used to speed up the processor. With a cache the device stores frequently used data next to the CPU so it can be accessed quickly. It's faster than reaching into the main storage area. (This is why it's a good idea to keep apps running instead of closing them).
More Apple A7 processor specs and unique features
There are other unique features inside the Apple A7 too. The A7 has an independent image processor. This image processor is a specialised digital signal processor used for processing images: recording colour, reducing noise and image sharpening. The independent image processor enables iOS devices to perform image processing with less distraction on the main ARM-v8-A CPU.
The new A7 also features a new area that Apple referred to as the Secure Enclave. This stores and protects the information on your fingerprint used by Touch ID.
Finally, there is the new Apple M7 coprocessor, which sits apart from the A7 chip and interacts with the sensors used by the iPhone (accelerometer, gyroscope and compass). Again, this frees up processing space on the ARM-v8-A CPU and also adds to the battery life of the iPhone.
How good is the Apple A7 compared to a desktop computer?
Recent analysis by AnandTech has shown that the Apple A7 chipset has the same number of execution ports as Intel's Ivy Bridge (used in Apple’s 2012 iMac, Mac mini and Macbook range) and reorder buffer equal to that of the Haswell architecture (used in the latest generation of Macs).
Anand Lal Shimpi from AnandTech analysed the Cyclone details that Apple recently revealed.
"Cyclone is a wide machine. It can decode, issue, execute and retire up to 6 instructions/micro-ops per clock," says Shimpi. "The same test on Swift [Apple A6] actually yields fewer than three concurrent operations."
"The Apple A7 also sports a 192 entry reorder buffer… Cyclone is big," says Shimpi. "It's bigger than anything else that goes in a phone. Apple didn't build a Krait/Silvermont [Intel's SoC for smartphones] competitor, it built something much closer to Intel's big cores. At the launch of the iPhone 5s, Apple referred to the A7 as being 'desktop class' - it turns out that wasn't an exaggeration."
Why has the iPhone 5s got such a powerful CPU?
Now that we have more inside details on Apple's A7 processor we can answer why the Apple A7 chipset is considerably faster than its rivals; what we can't answer is why Apple placed such a powerful system inside the current iPhone and iPad range. It appears that the A7 is not being used to anywhere near its full potential at the moment.
One slight oddity of the Apple A7 processor is that it appears too fast for the iPhone and iPad Air devices at the moment. There are very few applications that truly take full advantage of the power provided by the Apple A7 processor. Apple itself has not produced first-party apps that truly use all the power of the Apple A7 processor, although this could be because running it at full tilt uses too much power. It's also an oddity to have a 64-bit processor paired with a device featuring 1GB of RAM (one of the key advantages of 64-bit processing is the ability to access a block of RAM larger than 8GB).
It may be that Apple is future-proofing its internal components to have a technical edge on its competitors down the line, when the kind of performance offered by the Apple A7 is commonplace across mobile devices. It may be that the Apple A7 hints at Apple developing a SoC to replace the Intel processors used in its Mac OS X range of computers with ARM chipsets (it would not be the first time that rumour has done the rounds). It may be that Apple has a software feature in mind; one that requires short bursts of extremely high processing power. What that is, we can only speculate (although Siri offline functionality would be a good guess).
"Cyclone is incredibly forward-looking," says Shimpi. "It's very likely that you'll run into memory limits before you hit CPU performance limits if you plan on keeping your device for a long time."