How Apple's A7 64-bit chip gives iOS plenty of headroom for the future

How Apple's A7 64-bit chip gives iOS plenty of headroom for the future

Summary: Apple's new processor looks set to give Cupertino many more options than just more memory in a phone.


Much has been made of Apple's A7 processor's 64-bit support, and if it's built around ARM's latest architecture as that seems to imply, then there's a lot there's a lot more to the next generation Apple processor than we're seeing.

Because when you drill down into the silicon, ARM's v8 architecture does a lot more than just increasing the addressable memory.

16-09-2013 08-57-19
Apple's latest silicon: more than meets the iOS?

Perhaps the most significant change in ARMv8 is support for Type-1 hypervisors — something that's essential as it uses a virtual machine to run 32-bit code.

Like Intel's and AMD's x64 processors, a Type-1 Hypervisor lets you run virtual machines directly on the silicon, with separate partitions for each VM and no need for resource-hogging emulation layers. There's also support for common cryptographic algorithms in silicon, with instruction set calls that speed up access to the functions needed to deliver secure encrypted file systems.

So what can Apple do with a virtualisation-ready processor that can handle encryption very fast indeed, coupled with a biometric sensor?

One big problem facing mobile devices in the enterprise is how to separate the secure and the public.

BlackBerry has chosen to handle it in software using features of its QNX to build secure encrypted partitions for work and for home, but that required throwing away an entire OS and the ecosystem that had been built on it.

With WinRT (and Windows Phone) Microsoft has started the migration to an architecture that supports separate partitions for each application, by introducing deep sandboxing for WinRT apps with cross-sandbox contracts for inter-application communication.

With a virtualisation-ready processor in its new phone, Apple can now start to move iOS in the direction of a hypervisor-controlled sandbox environment, perhaps using a technology like Microsoft's research OS Drawbridge.

Here the operating system component of a VM is tailored to the application it is hosting – minimising the attack surface of each secure partition. Combined with a fingerprint sensor to identify users, Apple has the tools it needs to deliver biometric access control, allowing devices to support multiple users, with files and apps for one user hidden from another using hardware encryption.

While iOS doesn't support this approach currently, it's a logical extension of the current iOS security model, which uses selectively encrypted sections of the file system to secure application-specific data. It's also an approach that would allow apps written for an older version of iOS to continue to run, in their own dedicated partition, without the security features that newer apps, in their individual partitions, could use. That way there'd be backward compatibility, allowing Apple to deliver a more secure, enterprise-friendly, iOS without destroying its existing ecosystem.

ARMv8 is a powerful platform, and Apple's silicon designers will be adding their own features to their silicon alongside ARM's own technologies. That means there are many more options for Apple to deliver a next-generation operating system on its silicon beyond what we know about ARM's roadmap and technologies. Controlling its own silicon gives Apple a distinct competitive advantage, even when building on the same foundation as its competitors in the Android, Windows Phone, Windows RT and BB10 camps.

Whatever Apple is planning with the A7, don't expect to see any real benefits until iOS8, if then. What the iPhone 5s (and any future A7-based iPads) is, is a "get the hardware out there" play. Apple needs a critical mass of virtualisation-ready iDevices before it makes any significant changes to the OS – much like Microsoft had to wait for a critical mass of Xeon servers before making its server OS 64-bit only.

But when that critical mass is there? Apple will be able to quickly roll out massive changes to its OS with the minimum of disruption to users – especially with many of them upgrading their devices every two years. Until then, well, you're getting a faster SOC, with more features and improved graphics performance.

And further in to that future? As ARMv8 can be used to build "desktop-grade" processors, could we see Apple stepping back from Intel to its own ARM-based Macintosh hardware? It's certainly easier to use ARMv8 to emulate x86, and x64, instructions, so Apple could deliver an ARM OS X that could run existing code in a VM, with new ARM compiled code running in its own sandboxes. And that could be a very, very interesting tomorrow.

Further reading

Topics: Apple, iOS, ARM

Simon Bisson

About Simon Bisson

Simon Bisson is a freelance technology journalist. He specialises in architecture and enterprise IT. He ran one of the UK's first national ISPs and moved to writing around the time of the collapse of the first dotcom boom. He still writes code.

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  • The future??

    Meh... by the time phones need to access apps and the ram necessary for this Apple will discontinue support for this phone.. They want you to get a new one every year anyway.
    • Not Sure Where The AUthor Was Trying To Go

      I can sort of see this in a tablet (maybe at best?) but in a smartphone?
      So in agreement. Going to 64 makes no sense at all in a handheld device and is actually more of a detriment than anything.
      Not sure what Apple's game plan is.
      • Don't get me wrong

        I could care less if they went 64bit and it is probably the right thing to do but the way these bloggers praise it like it will give the smartphone so much better computing and how they can add more ram is just ridiculous. What so they can update their Facebook and Twitter a microsecond faster and have an edge on playing Candy Crush.

        Like you said maybe in a tablet but even then the tasks those are used for are fairly light with many people having remote services that connect to an actual computer or virtual computer of some sort remotely for their computing needs.
        • Think of other Apps

          While facebook and candy crush probably won't see anything noticable from going to 64bits, many other apps will.

          Camera apps will be able to chew through data much quicker, this should make real time effects more efficient as well as stuff like face recognition, or automatic photo selection, etc. Same with videos. Compressing and editing 1080p video or even future 4K video will benefit from the jump to 64 bits.

          The same with security with encryption, decryption, hashes etc.

          There is a real use for this technology today.
          • RE: Think of other Apps


            People seem to focus mostly on the >4gb memory addressing and ignore the rest of the new features of the chip (hypervisor thing is nice, but there was also virtualization support in ARMv7).

            The additional (and 64bit) general purpose registers (31 up from 14) and 32 128bit registers in the SIMD (NEON, up from 16) can be a pretty big deal, as is the AES encryption functions added to the SIMD .

            There are also a bunch of other enhancements over the previous ARMv7. Its more then just being able to address more then 4gb (which is more of a side effect of going 64bit then the primary reason).
          • People seem to focus mostly on the >4gb memory addressing

            That's because that is the primary advantage of a 64 bit architecture by orders of magnitude over any other aspect of a 64 bit architecture. The other advantages do not factor outside of arena of encryption.

            The chip has other features which surely will give better performance, but making it 64 bit as opposed to 32 bit without adding the extra RAM will not cut the mustard.

            So not exactly. On the contrary, completely the opposite. Photo apps will have to be rewritten to take any small advantage of the 64 bit architecture. Recompiling without rewriting will make apps slower.
          • I see your point

            You're right for those things but I guess I do not see many professionals using their phone for their pictures and movie shooting. To me the lenses the can fit into these small devices (even with attachments) are the biggest drawback of achieving anything of great quality to achieve the image/video requirements of these high quality photos and videos
          • Professional use of a smartphone

            It is very unlikely any professional will use any smartphone for anything other than auxiliary device.

            The number of professional photographers is much less than the number of "other" people, who will prefer the convenience of the smartphone camera and being always connected --- instead of an high-end camera. Most "normal" people will never agree to spend the time and effort (not to say the money) involved in learning to use professional tools. The iPhone camera is for these people. Not for "professionals".
          • Pros and semi-pros can play....

            First, I know several pros doing much of their less demanding shooting on their mobiles.

            Second, the new Sony "Lens Cams" that can be a good distance from the phone points to a future of more serious photography being done on (or via) mobile platforms. Meanwhile the hardware/software combos of the Lumia 1020 and iPhone 5s are, at least as single focal length cams, innovative in their own ways and "good enough" for the ultimate (non-printed) destination of more and more photography: the web.

            It's really quite amazing how individual prints and magazine pages - kings of the imaging output hill for over a century (longer for individual prints) - are increasing niche markets.

            Third, with Android migrating into cameras, allowing more post-processing and digital posting/sending on cam, only a matter of time until a major smart phone maker returns the favor and crams an optical zoom into a smart mobile's innards. Casio demonstrated this could be done in small form factors by redirecting the optical path by 90 degrees something like 20 years ago.

            I'd def consider a phone with this feature - including paying another hundred and toting an extra oz around, e.g., to get it. Best cam being the one you have on you, "device converge" and all.

            Finally, much of photojournalism IS increasingly be done on smart phones. Sometimes brilliantly - remember that talented photogs can still make great images with nearly any gear and learn how to mine any platform for all it's worth.

            And sometimes badly and out of necessity, e.g., when an old-line Chicago paper (sadly) sacked its 20+ photographers, it announced it was offering "training in iPhoneography" (or some term like that) to its print reporters, expecting them to get photos for the story themselves.

            Whatever, we're nowhere near the ceiling for "real" photography on pocketable smart mobiles (however surreal it gets).
            Ice Cowboy
          • Re: Pros and semi-pros can play....

            The difference between the "professional" and "enthusiast" is very pronounced, but is not in the gear they use. Using the same equipment as an "professional" does not make you one.

            The professional's primary goal is to do the job, for which they are hired. Each time. Every time. Because of this, professionals tend to pick up tools that are reliable and produce repetitive results. The professional targets the predictable, "good enough" result. Or they don't get paid. They absolutely do not care about the "bells and whistles" of the stuff, only if it is reliable, they know it well and it does the job. If someone cares about the bells and whistles, then that person is not a professional.

            The enthusiast on the other hand, it set to "achieve" something. Be it the greatest photo of that eagle, or the most detailed picture of the forest where you can count leaves, or that wonderful (no one can explain why) sunset. An enthusiast can at times achieve "greater" results than a professional. But sometimes the result is mediocre or bad. Enthusiasts target the peaks. There is a category of enthusiasts that fail in love with the technology they use, and those are commonly known as fanboys, or techno-masturbators -- because they are so excited what a particular tool can do.

            The smartphone cameras are still awful for some tasks, such as anything that moves. Even compact cameras are still not good enough for this (except special purpose built ones, that are not generally popular, because they "suck" big time otherwise). Those who need to make such photos, will never use a smartphone, if they are professional, because well... the result is unpredictable. There might be cases of course, or tasks, or assignments that might be shoot with a mobile phone camera, but those are few and no sane professional would go without a reliable gear to be sure they did the job. Or, they don't get paid!

            While the above discusses photography, it equally applies for other areas where technology is used, including computers. In any of the cases, you are not a professional if you are a fanboy. Now, fanboy and fan are different things, but.. that's for another topic.
          • Well, no

            Very little about photo and video benefits from 64-bit processing. Faster processing, sure. Better floating point, better vectors, in some cases. But long integers are not a part of this. More memory, sure, once that's actually available.

            As well, no mobile devices are using the CPU for video compression/decompression anyway. Not that you couldn't, but it's a terrible way to spend your battery, since the on-board hardware AVC encoder/decoder does this with a tiny fraction of the electricity.

            Same with security... these are hardware functions. Or they are on other people's SOCs. There is mention of some crypto support in the A7 hardware; if they didn't have it before, they're behind much of the industry on this. That's AES, DES, SHA, RC4 etc. in hardware these days.
          • Well yes

            integer pointer math, caching along with significantly faster data streaming. As far as addressable memory. The stack and the heap are 48 bits apart instead of 24 bits. All these other coprocessors and signal processors and the new M7 need addressable memory and now they can have as much as they need for beyond the foreseeable future.

            It gives Apple incredible room, latency, and bandwidth. There are so many processors working asynchronously not to mention the GPU processors who are also part of that unified memory model. And who knows if they haven't implemented the heterogenous unified memory model that AMD has been pushing for general adoption and that we are seeing in the newest gaming consoles just coming out. It appears they are, based on the demo we saw at the processors introduction.

            It's a beast of a SOC and it got legs.
            Jack Zahran
          • Re: Very little about photo and video benefits from 64-bit processing.

            This is not even partially correct. Consider the following examples:

            1. You have an 32bit CPU, with no SIMD instructions (like ARM without NEON). You can only do 32bit calculations between registers and you usually have few of these. If you had 64bit CPU, then you would be able to process larger chunks of data at once, for the same time and power spent and thus will do the job quicker. You will also likely have more registers and this will further speed up the processing.

            2. You have 32bit CPU with SIMD (for example, Apple's A6). You won't do anything using the 32bit registers. You will instead use the 128bit NEON instructions. Thing is, the A7 now has double the number of NEON registers and this further speeds up processing. Because it already has 32 NEON registers, it might be possible to do a more of the processing (matrix operations, common in photo processing) in CPU registers, which will increase performance much, much more.

            Of course, you can argue that some media decoding/encoding functions are "hardware functions". Correct -- those are in the CPU. You make the CPU faster, with faster memory bus etc, and those other functions speed up as well. As for AES, SHA etc -- yes, some processors do it in hardware. The new A7 in particular, by virtue of using the ARMv8 instruction set has these in the SIMD registers, which lets it work on larger chunks of data "in hardware" == faster. You can always have several other chips that do special-purpose tasks -- but if you can fit it all in the CPU SoC, you achieve the same task, faster (common cache, memory bus etc) and consume less energy.
          • Camera apps will be able to chew through data much quicker

            No. They will not.

            All apps will have to be recoded from the ground up to take whatever minor advantages they can get from a 64 bit architecture without a relevant amount of RAM to address and take advantage of.

            Since the 5S will have 2GB of RAM there is no advantage whatsoever in a 64 bit vs 32 bit version of this processor.

            Marketing spiel from the iTards again, making something out to be a massive advantage when it patently is not, and will continue to disappoint the iTards until any phone has the RAM to address more than 32 bit can handle.
        • Don't fall into that trap

          "640K is all a PC will ever need" or something to that effect.

          A corollary to Moore's Law is "What is fast today will be slow tomorrow."

          Very few people can envision a future beyond 4-5 years (I can't), but I do think that uses for technology will be surprising and exciting. A mobile 64 bit chip is an enabler to that future.
        • I don't understand either

          Arm comes up with a reference standard for 64 bit, and all the Arm players are currently developing 64 bit. Apple's solution has always been a bit slow compared to competitors, so this is sorta a catch up in speed. OK so Apple came out about 3 months ahead of the competitors with a slower implementation, and the others will come out with optimized ones in 6 months to a year.

          Don't understand the fuss. Not like Tomb Raider is going to play any faster anyhow.
          • Still not seeing why

            What does 64bit buy us in a smartphone?
            We aren't doing hidef compressible video or running a server. Apple isn't going to gift us with >3gb of RAM. The avg dev is not going to recode to take advantage of 64 bit and just recompiling for 64bit just bloats an app potentially eating mem, slowing an app down and impacting battery life.

            So, where is the benefit?
          • Re: What does 64bit buy us in a smartphone?

            Better user experience.
          • Better user experience.

            Absolute BS. The Samsung Note 3 is processing 4K video with a 32 bit processor. You are full of specs, but short on knowledge Bambi.
        • I could care less if they went 64bit...huh?

          Do you mean:

          "I couldn't care less if they went 64bit"?