Home Business IT Technology Just what is a 64-bit Apple A7 chip?
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Apple's A 7chip remains an enigma despite many journalists' best attempts to get Apple to reveal its secret sauce architecture.

Apple remains tight lipped - "It is a 64-bit ARMv8 based chip that runs a 64-bit version of iOS which in turn runs both 32-bit and 64-bit apps.".

The ARM v8-A is the basis of the Coretex-A53 and A-57 family – these go under the code name X-Gene, Denver and now Apple A7. The only licensees of the 64-bit processor are AMD, Broadcom, Caixeda, HiSilicon, Samsung, and STMicroelectronics. 9to5Mac reports Samsung is supplying this system on a chip (SOC) to Apple.

And, for your imformation, current 32-bit ARM processors in use by competitors are based on the V7-A architecture, and go under the code names Krait, Scorpion and Apple A6/6X, as used in the iPhone 5 and now 5C.

A little more digging shows that the A-53 and A-57 in full 64-bit mode will deliver up to three times the speed of the V7 SOC, while Apple’s claim is twice the speed.

The speed claim is highly suspect in a mixed 32/64-bit app environment - 32-bit instructions are executed under the control of a 64-bit hypervisor. Simply put, it creates a 32-bit virtual machine that runs 32-bit software in a virtual operating system. This has significant memory and processing overhead for 32-bit software, and Apple is a very long way - years at best - from having every app converted to 64-bit.

The A-53 operates in big.LITTLE mode (where lower and higher speed cores load share for maximum battery efficiency). The A-57 is a single thread, multicore, processor, where high-speed cores do everything at the expense of battery efficiency. We assume that it is an A-57, unless its M[ysterious]7 processor is actually a big.LITTLE processor. If that was the case, however, Apple would have shouted that from the rooftops.

The A-5X series central processor units (CPU) support:

  • Cryptographic acceleration that speeds up authentication (hence the fingerprint recognition is possible)
  • Integration with the Mali based graphics processors units and OpenGL ES 3.0
  • Improved image signal processing (better camera specs like image stabilisation, colour correction and light balance)

Opinion

Apple has been guarded about this SOC, but we don’t know why. It is safe from competitors trying to emulate it.What it is not safe from is that any competitor can use an ARM v8 processor and do the same thing. Android does not yet support a 64-bit OS or dual 32/64-bit processing. Maybe next year.

The main issue is in comparing ‘horsepower’. There are few real-world benchmarks, and performance tests, that can compare one smartphone to another. The ARM world has hidden behind this. At best, we understand that a V7 (previous generation) was about 20 times less powerful than an entry level Intel Atom, so a V8 may be 10 times less powerful. Who knows?

ITProPortal states that the chip reaches 20,500 MIPS in full 64-bit mode. That is a long way from the Samsung Exyons 5 Octa that reaches 30,000 MIPS (pre its big.LITTLE announcement).

To finish my critique, I suspect that the specifications are as follows:

  • 1.7GHz, dual core, A-57. It could be a quad core but battery life becomes an issue. I don’t think it is a big.LITTLE implementation.
  • 1GB of DDR3-1333 RAM on the SOC – it is unlikely to have more for power consumption and cost reasons.
  • Power VR Series 6, G6400, four-core, 28nm, as Apple has a licence to use this tech.

Unfortunately the M7 (M for mysterious) has even less public information, so all I know is that it is part of the SOC, and probably not a Core processor at all, but just a marketing name for an accelerometer, gyroscope and compass. It apparently has context awareness and apps will need to develop specific uses for this co-processor.

Do we really care? Apple simply says that you do not need to know what is under the bonnet but that it simply works. Call me old fashioned but I want to know.

ITProPortal states, and I concur:

None of this means that the A7 won’t be faster than A6, but it does mean that the 64-bit status of the A7 is a marketing tool, not a genuine performance boost. The major reasons for adopting 64-bit architectures simply aren’t present in mobile devices. It’s not clear that a phone with 4-8GB of RAM ever makes sense given current constraints on battery life.

The blend of 64-bit and 32-bit software means the A7 will offer strong performance in both categories (which is good), but won’t automatically have a clear benefit from doing so until the entire application stack has switched over. That’s not going to happen for years yet, given that iOS7 supports all iPhones going back to iPhone 4.

For all the noted new features of the iPhone 5S, this 64-bit switch is almost entirely marketing fluff. It’s not going to be the key to the SoC’s higher performance. That’ll come from architectural improvements Apple integrates into the phone’s handling of 32-bit code for at least the next 6-12 months.

Having made it this far have a look at a few parodies of the new iPhone here – it may give you a laugh (particularly the 5C promo). PS - Don't believe that these were done by Microsoft.

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Ray Shaw

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Ray Shaw ray@im.com.au  has a passion for IT ever since building his first computer in 1980. He is a qualified journalist, hosted a consumer IT based radio program on ABC radio for 10 years, has developed world leading software for the events industry and is smart enough to no longer own a retail computer store!

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