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September 12, 2013
According to what we've seen so far, Apple's new 64-bit iOS will be faster than its 32-bit counterpart, but don't expect
that the CPU's speed and the phone's overall features will double in performance because they won't. But you will definitely see
a speed improvement, it's a given.
Apple did say that the chip is compatible with all the iOSs out there that are still 32-bit. For the moment, that is all third-party
programs and mobile apps.
For now, Apple hasnít said how much RAM the new iPhone 5S contains, but itís not going to be of the order that the new 64-bit
processor makes possible.
As things stand now, software running on the 32-bit ARM processor family used by Apple can access up to 4 GB of virtual memory, and
the chip can potentially access up to 1 TB of physical memory, thanks to a 40-bit physical address width, which is a cool improvement.
However, thereís still no sign that iPhones will gain that much RAM in the near future and certainly not the 256 TB of physical
memory the new A7 can easily address.
Although pointers into virtual memory can be 64-bit wide on that new processor, the chip's architecture defines a 48-bit physical
A lot of software could use some extra headroom with 64-bit pointers, although that may boil down to effectively 48 bits of useful
virtual address space per app. Keep in mind that the upper bits are being reserved for the operating system and some unmapped space.
So why throw in a 64-bit CPU if it won't improve the overall performance of the device in a meaningful way? The cynic might say
that itís nothing more than a marketing pitch.
Of course Apple is very keen to claim it was the first and the only phone maker to put a 64-bit chip in a smartphone, well at
least for now anyway. The company will probably make the same claim for its iPad when it upgrades the device to the A7 chip shortly.
Can you blame Apple for doing such gimmicks? Probably not, but then again, some might not agree with all the hoopla.
Nevertheless, Apple is pitching improved performance-- up to twice the performance of the 32-bit A6, it claims. To provide that
performance enhancement, the A7 chip contains twice as many integer and floating-point registers as its predecessors do.
That allows the processor to be loaded with more data all at once, in turn meaning there will be fewer subsequent cache or memory
accesses. The result is that the coreís arithmetic units spend less time standing idle awaiting numbers to crunch.
Apple is telling iOS app developers that focusing on the use of 64-bit integer maths is a particularly efficient way to take
advantage of the new processor.
Likewise, making use of ARMís NEON instructions is the architectureís long-awaited answer to Intelís SSE single instruction
Appleís new A7 chip is based on ARMís 'v8' design, which also incorporates instructions to accelerate the AES and SHA-1/SHA-256 cryptography
algorithms. Apple itself is likely to be using these in its Touch ID biometric control mechanism as well.
Those advantages are all well and good for 64-bit apps, but not for 32-bit code. Apple itself admits that 32-bit code wonít run
as quickly or as efficiently on the A7 as a 64-bit version of the software will.
Additionally remember that implementing 64-bit code has a downside as well-- when your data units are twice as big, a long integer
takes up four bytes on an A6-based iPhone, but eight bytes on an A7 device, for example, so you'll need twice as much memory to store
the same amount of data.
Appleís iPhone 5S tech specs donít reveal how much memory has been built into the 5S, but 2 GB, double the RAM fitted to the A6 and
A6X chips seems likely, especially given Appleís claim that the A7 has more than a billion transistors on board.
And using more bytes to store a specific value also means that the host chipís caches become less capacious as well, and that
can degrade performance on certain apps that are more CPU intensive.
Again, Apple hasnít revealed how big are the A7ís caches, though itís widely being assumed for the moment that the A7 contains
the same 32 KB instruction set and data caches, and a 1 MB L2 cache as the A6.
When the iPhone 5S launches a 32-bit app, iOS 7 has to load 32-bit versions of any system frameworks that the app uses. Thatís
in addition to the 64-bit versions of those libraries the operating system may already have loaded into memory.
Again, this increases the active appís memory footprint, meaning that the operating system needs to be more aggressive in
'parking' background apps out of RAM and into the Flash storage.
Having both 32-bit and 64-bit copies of all the system frameworks increases the amount of storage space the OS takes up as well, though
fortunately even on a 16 GB iPhone 5S, it shouldnít prove much of an issue to filling a phone with apps and content.
All of Appleís own apps have been recompiled to work with the 64-bit iOS runtime the company said, so it really will be third-party
apps that slow the system down.
No wonder Apple is keen for coders and app developers to begin upgrading their apps to include 64-bit code-Ė iOS app binaries
can contain both 32 and 64-bit versions, but that code very likely needs to be optimized for the 64-bit environment to make sure
it gets the most out of the performance advantages the A7 offers.
Given how many third-party apps are out there, itís going to take some time for a significant percentage to support the new 64-bit
runtime. There are many apps available today that were designed for much earlier versions of iOS and may not get iOS 7 makeovers, let
alone 64-bit conversions.
Even mobile apps that are updated in this manner may not show an immediate twofold performance increase of the kind Apple is
Thatís why users are unlikely to see any obvious increase in battery life. Faster performing apps get the work done more quickly than
they once did and that allows the processor to spend more time in a low-power state, reducing the drain on the battery.
But if those faster-performing apps arenít there to begin with, thatís not an advantage users will see, at least not for now.
Naturally, recasting iOS as a 64-bit operating system puts it on par with Mac OS X, which migrated to 64-bit more than seven years
That might suggest closer integration of the two operating systems, though thereís plenty of code in each thatís not relevant
to the usage model of the other, so we'll have to wait and see.
And what about iOS-based iBooks from Apple? Itís possible, but we don't think the company will make the same mistake Microsoft did--
trying to make the primary user interface of a keyboard-based device a tablet-centric one.
In other mobile news
In 2014, people in London England will get access to 72 MHz unlicensed radio spectrum, all in the prime sub-1 GHz band, as its wireless
country regulator Ofcom prepares to open some TV airwaves to anyone with a working database.
Ofcom's new plans on opening up White Space frequencies pinpoints London as the biggest winner thanks to the presence of
the Crystal Palace transmitter, which transmits TV frequencies to most of the capital, leaving the signals used by neighbouring
Less well structured is Glasgow, where the primary transmitter is too far from the town centre and leaves only about 60 percent
of its citizens with 27 MHz of shiny new radio spectrum that will be available to nine in ten British households sometime early next year,
if all goes according to plans.
The 2.4 GHz Wi-Fi band is 83 MHz wide and has changed how the British perceive mobility. Wireless provider 'Three' runs a national mobile
network with only 74.1 MHz, so the prospect of a similarly-sized chunk of radio spectrum falling into public hands early next year can be
viewed as exciting.
Overall, White Space radio uses frequencies which are being used somewhere else, but are locally empty, so some management
is necessary. The frequencies used to transmit TV in Slough are different from those used at Crystal Palace, to avoid interference,
so the Slough frequencies are empty in Islington where they can be used for short-range wireless or point-to-point links.
On booting up, a White Space access point contacts Ofcom to ask for a list of approved databases, then contacts another database
with its location and the radio protocol it would like to use.
The database then responds with a suitable frequency and power level which the access point passes on to connecting devices.
It may sound complicated but it works. White Space devices, and the associated databases, have been operating in the U.S. since early
this year. Britain is a lot smaller and more reliant on Freeview (digital terrestrial TV) which stands to lose most if it all goes
So the industry has been waiting to see just how conservative Ofcom would be in permitting the utilization of TV White Space, and it
turns out that Ofcom isn't feeling very conservative at all.
In its consultation, Ofcom outlines the power it's minded to permit, and how it will protect Program Makers and Special Events from being
PMSE users have been wandering in the TV White Space segment for several decades already, and are concerned of the newcomers, so
they'll get priority access.
That simply means that anyone living near Wimbledon should be aware that their White Space allocation will reduce significantly during
Ofcom says that the U.K. has 24 such events annually, so perhaps it's not the ideal technology for streaming sports coverage.
Additionally, White Space users will also be banned from approaching within 14 meters of a PMSE user. Their device will have to switch
frequencies, or switch off, which should keep them outside the studio or theatre.
You might reasonably ask what happens when someone tweaks their White Space equipment to use the whole band, knocking out TV
reception and radio mics alike, but in reality, that's already happening.
White Space equipment is required to be tamperproof and resistant to replacement firmware, which might make it more difficult to modify
than for example existing Wi-Fi routers.
Wi-Fi offers better range and capacity, but few people bother. Ofcom's more relaxed approach is down to the temporary nature of White
Over the next six months, Ofcom will be running some trials, in London and elsewhere, to see just how much interference these White
Space devices kick out, and Ė perhaps more importantly Ė whether anyone cares.
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