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What is 64-bit? iPhone 5S A7 chip explained


A7 64-bit

The arrival of Apple’s first 64-bit smartphone has been overshadowed by the iPhone 5S’ updated camera and the colourful iPhone 5C, but it’s a big deal that has huge ramifications for every future Apple device – as well as Intel, Google, Samsung and ARM. Mike Jennings explains the technical side and the implications for future iPhones, iPads and their Android competitors.

SEE ALSO: iPhone 5S features: killer or just full of filler?

What is 64-bit and how does it work?

The term “64-bit" refers to the way processors handle calculations. It concerns the maths performed by computers at their most basic level: “bits” are tiny units that have values of either 0 or 1, and these are manipulated by the processor and written to a PC’s memory in order to complete tasks.

Smartphones that use older 32-bit processors can only work with data strings that consist of 32 characters – so they have a maximum range of just over 4 billion numbers. A 64-bit processor has a much larger range because of the increased number of digits available – data can be processed 64-bits at a time, rather than in 32-bit chunks.

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Imagine it this way: a team of 32 codebreakers at Bletchley Park try to crack the same code. It’s slow work – but double the codebreakers and it’ll be finished faster.

Or try this: you send 32 assistants to collect 128 items from the same shop. The 32 assistants will require four trips – but if you’ve got 64 assistants, they’ll only need two.

A 64-bit architecture is faster, gets more work done and is more efficient.

The 64-bit A7 processor in the iPhone 5S uses the ARM v8 architecture. It’s the first time this new chip has been used in a smartphone, and Apple claims it’s got twice the power as the A6 chip in the iPhone 5.

A 64-bit chip brings the iPhone 5S into line with the rest of the computing world. AMD and Intel have made 64-bit PC processors since the turn of the Millennium. The PS4 and Xbox One consoles both use 64-bit AMD chips.

SEE ALSO: Xbox One vs PS4

Does 64-bit bring real benefits?

The main benefit concerns the speed of mathematical calculation, which we’ve detailed above. The other big improvement concerns memory: a 64-bit chip can address more than 4GB of RAM, which 32-bit chips just can’t manage. It’s not an issue now, as no iPhone or iPad has more than 1GB of RAM, but it could be a few years down the line.

The added power of 64-bit will improve iPhone 5S performance in a number of areas. The encryption used by the phone’s fingerprint sensor will be satisfactorily fast, and the camera’s new features will also work smoothly with the chip’s improved computational ability.

These high-end applications – as well as photo and video editing and encoding, for instance – are faster with 64-bit. Games, too, benefit – at the iPhone 5S launch Apple demonstrated Infinity Blade 3, which likely wouldn’t be possible on 32-bit.

Apple’s iOS 7 has been re-engineered to work with 64-bit, and that means the OS will feel butter-smooth. But, given the simplicity of many smartphone apps, it’s a fact that many just don’t need the added power of 64-bit right now.

Most developers won’t have advance access to Apple hardware, so it’ll take time for 64-bit apps to arrive. Thankfully, the new processor is backwards-compatible with 32-bit software.

Future Apple processors, whether in iPhones or iPads, could have enough power to run console-quality games and PC-quality apps. The shared architecture could even make it easier to port software to iOS devices.

One of the key benefits right now is marketing – Apple’s the first firm to us a 64-bit smartphone processor, and that brings plenty of kudos, even if the real benefits won't arrive for a little while yet.

What are the long-term implications?

Despite the immediate performance boost, the move to 64-bit is more important in the long-term.

In a year or two, Apple’s phones and tablets – and every competitor – should have 4GB of RAM alongside a 64-bit processor, and Cupertino’s software teams and third-party developers will have had more time to get the most out of this new architecture – an important head-start over Samsung and Google.

That expertise will have big implications: the iPhone may use more efficient chips with better battery life. The iPad could become even more powerful. Apple may have ARM processors with enough grunt to power laptops.

It ties in to Cupertino’s long-term vision for “platform convergence” – a strategy that may see phones, tablets, laptops and other devices share hardware and software.

The Apple A7 chip means the iPhone and iPad now share the same 64-bit system as Intel, and iOS and OS X already share the same kernel and developer environment. Apple claims the A7 is a “desktop-class” chip, so it’s no stretch to imagine more powerful parts inside laptops.

Apple has also taken charge of graphics: previous iPhones and iPads have had PowerVR GPUs, but this time it’s described as Apple’s own chip.

It’s not just hardware. Its OS X desktop system borrows features from iOS in every new version now and if Apple can use ARM-based 64-bit hardware across more devices, a universal store and unified software could follow.

What about demanding tasks that need Intel power? That’s where the cloud could take over. It’s a long way off, but Apple has already worked on hugely upgraded cloud facilities: in 2010 it built a data centre in North Carolina for iCloud, and reports indicate the facility only opened with 20,000 servers – despite that location having room for about one million servers.

While its data centres use Intel Xeon hardware, it should be noted that ARM-based servers already compete with Intel in some benchmarks, and AMD has ARM-based 64-bit server chips on its roadmap.

The bottom line

Apple’s move to 64-bit will make the iPhone 5S more powerful, but an obvious impact won’t be felt until developers begin to release apps that make use of the new A7 chip.

The 64-bit ARM chip and its successors will ensure that the next iPhones and iPads are barnstormers, and they could help console-quality games and PC-quality applications become more prevalent on these devices.

It’s bigger for Apple’s long-term future, though: a 64-bit processor signifies another step in the convergence strategy that could see iPhones, iPads, laptop and even desktops sharing hardware, operating system and software.

Apple is the first smartphone firm to make the jump to 64-bit but, now, everyone else will follow suit – and that’s only good news for consumers. It might look like overkill, but Apple’s move to mobile 64-bit is a crucial step for proper progress – and could point towards an ARM-based future.

Mike Jennings is a freelance tech writer. He spent five years as senior staff writer at PC Pro, and now writes about components, PCs, smartphones, tablets and laptops. He tweets from @mikejennings.

Next, read our iPhone 5S vs Galaxy S4 comparison

Chris M

September 12, 2013, 8:55 pm

What a load of made up rubbish. The Apple A7 does not share the same 64 bit system as Intel, and the following quote is a complete fabrication: "Future Apple processors, whether in iPhones or iPads, could have enough power to run console-quality games and PC-quality apps. The shared architecture could even make it easier to port software to iOS devices."

There is no shared architecture. The important part, the ISA used by the CPU is utterly different and completely incompatible. A 64 bit A7 is no more able to run Intel x86-64 instructions than a 32 bit A6 or a cabbage for that matter. Software cannot be shared across desktop and mobile CPUs without recompilation to take the differing instruction sets into account. Consoles and iPhones will not run the same code. ARM CPUs for all their benefits do not compete with Intel CPUs in the data centre - they have vastly different performance characteristics and compete in different market sectors.

In terms of its use within a phone, 64 bit will have no impact on the end users or the performance of the user interface. *Some* mathematically complicated calculations performed on large chunks of data may run a bit quicker, but with the volumes of data processed on a phone there will be no discernable benefit outside some very niche applications.

Apple only moved to 1GB RAM with the iPhone 5 and hasn't seen fit to expand upon that in the 5S. The 4 and 4S had 0.5GB RAM. I can't see Apple suddenly expanding to 5+GB of RAM any time soon, so again the benefit won't be felt for years.

Just about the only factual statement was the one that says that the immediate benefit is one of marketing. Clearly that is having an impact with ridiculous fluff pieces like this tarring the once *Trusted* Reviews.


September 12, 2013, 9:09 pm

Pretty poor discussion of 64 bit benefits. Moving to 64 bit has no inherent performance advantage which this article suggests it does.


September 13, 2013, 8:04 am

A 64 bit cpu versus 32 bit generally have twice or more registers available for the compiler to optimize code with and the increase in data locality given by more registers has a first order effect on performance.

For example on UNIX, due to more registers being available, when a function is called more of the parameters being passed can be copied to a register rather than being copied to memory. You will not see the effect of this optimization on windows as the number of register available for function calls being the same on 32 and 64 bit systems.

More registers also helps with having better data locality with local parameters within functions as well.

etc. etc...

The upshot is just by switching from 32 bit to 64 bit will give you a performance increase of 80 % for c++ code. Java and c# don't seem to follow this rule last time I looked.

Mike Jennings

September 13, 2013, 9:31 am


Thanks for your comment - sorry that you disagreed with some of the points I made in the article.

It's an article that in part looks at the potential future for Apple, so of course there's some speculation there. I'm sorry that I wasn't clear enough when talking about the shared 64-bit system now used by both Intel and ARM chips. I didn't mean that iPhones and iPads would be able to run console games and PC software without any headaches - only that it will be a little easier for that to happen in the future.

Regarding the performance boost from the new 64-bit chip to the existing iPhone 5s, I agree that performance boosts right now will be limited to high-end applications and games rather than simpler apps.

And, again, the move to 64-bit isn't about iPhone, as you're right - it'll be a long time before it moves to 64-bit. It's a change that will be felt across a much bigger selection of Apple products.

Thanks again,


Ryan Kramer

September 13, 2013, 3:00 pm

Not true in this case.

"The A7 CPU has 31 general purpose registers instead of 15, 32 128-bit vector registers instead of 16, and can perform double precision floating-point arithmetic on vectors, which previous CPUs can't do. That will make most code a lot more efficient."


September 13, 2013, 9:31 pm

can't believe how aggressive people on this forum get.


September 14, 2013, 11:25 am

.. and here i was thinking the the one real reason they went for 64bit was the fingerprint scanner and security reasons..


September 15, 2013, 7:48 am

AFAIK 32 bit OSes CAN access more than 4GB of RAM (through PAE), eg Windows Server 2003 DataCentre (32 bit) supports 128GB RAM.
Isn't the key difference the ability of programs in a 64bit environment can access more than 4GB?


September 15, 2013, 9:41 pm

Chris, both architectures are indeed different, one is a complex instruction set, and the other is a reduced instruction set for starters. But I think Mikes point is that it should make things easer to port. eg. in programming you have to deal with lots of what are called structures/types, knowing that you can always do Int64 etc, is very nice. 64bit is not just for memory access, what about accessing Storage, at the moment to access storage greater than 4Gig, Apple must be implementing a Sector/Offset algorithm when accessing this, having a simple 64Bit reference just makes the code cleaner. Also from what I can remember of RISC processors the 64Bit is a mixture of Op Code & Address & Register all in one, so this meant that most operations could be done in 1 clock cycle, so having a wider 64bit access should also mean more operations could be made to use 1 clock cycle, having benefits on performance. Intel processors use CISC so this advantage wasn't seen as much. But it's not all good news going to 64bit, as Windows users found out when first going from 32bit. 64bit instructions / addressing means more data going into the pipeline/bus, and moving more bits of information inside CPU/pipeline can be expensive, this is were a good CPU cache helps.


September 16, 2013, 5:41 pm

You seem to be overall unclear on the concept. Registers are not persistent storage, all user data has to be brought to the registers to be read or written to, and then back to memory in order for the changes to be preserved.

More registers are useful in the context of inlining, which is translating functions to linear code rather than calling the actual funciton, which is more expensive.

I work with a lot of heavy duty HPC code, and I can assure you 64bit C++ compiled code is not even noticeably faster than the same code compiled 32bit, despite the fact it has twice the registers available. There is a very limited set of workloads which can noticeably benefit from more registers , none of which are ran on ... mobile phones. Floating point numbers use special registers, so increasing the width of general purpose registers to 64bit will not benefit the performance of floating point number crunching, not to mention most of the performance sensitive code is executed on SIMD units, so the only potential benefit from switching to 64bits is for 64bit integers, which are numbers way too big to be practically useful in an application, running on a mobile phone. What kind of a mobile phone application requires 19 digit numbers? This is Quintillion range, or a billion billions. Certainly an overkill for 99.99999999% of apple users, which need a phone to mostly take duck face photos in front of bathroom mirrors.

In the case of apple, it is completely a PR stunt to impress people who don't know any better than comparing numbers. If anything, 64bit code will consume more memory because pointers will take up twice the memory. There is no point of switching to 64bit if you are not going to make use of its main benefit - more addressing space. I've seen quite a lot of people for which the PR stunt worked, people who literally bought it that 64bit is twice as fast as 32bit. 64bit machines can be twice as fast, or even way faster than 32bit machines in a single context - where a lot of memory is required, which helps avoid swapping, since virtual memory is TREMENDOUSLY slower than ram. But outside of that narrow context, 64bit doesn't offer much improvement. Unless you count vanity of course.


September 19, 2013, 11:27 am

Anything above 4gb on a 32 bit os that uses PAE is slower than an OS using over 4gb that is 64 bit. Whether this actually provides any meaningful performance gains I do not know, just thought i'd mention it.


October 27, 2013, 6:58 pm

Which has nothing to do with being 64-bit, you could add all those things to a 32-bit version too.

Ryan Kramer

October 28, 2013, 8:17 pm

Read up at the very least on the apps that use video. 32-bit wouldn't be the same.

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