A glance at Apple's next iPad, iPhone chip

This morning's hottest Apple rumor claims the company will introduce new iPads with a much faster processor early next year. Apple is also expected to deliver the much-discussed iOS-wielding Apple TV in January, when a new metal-backed CDMA-model iPhone 4 will reach Verizon in the US and also China Telecom abroad.

News that Apple will finally move to embrace the multicore ARM Cortex-A9 processor is hugely important. Apple had originally been expected to field this reference design in its first-generation iPad.

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It didn't.

Instead, it is thought Apple deployed its version of the ARM A8-based processor (called the A4 by Apple) in the iPad, and later inside the iPhone 4.

I imagine we'll see this also appear in the future iPod touch.

Some speculate it could even end up becoming the brains inside the next-gen Apple TV when that is revealed.

Look at the past, see the future

So, Apple's decision to field a processor based on the ARM A9 is important because it is likely the chip will power most Apple mobile devices in future.

When Apple developed its A4 processor it took pains to tweak the best battery life it could from the device. On the iPad, it sips power at a nice and low 2.5 Watts, which is why you can get all that battery life (ten hours) from the processor.

Otherwise, the A4 is a single 1GHz processsor, with memory and graphics chips sandwiched inside the same die as the processor itself, with a nod to Intrinsity, which handled some of this work and was later purchased by Apple.

So, what Apple did with the A4 was push for as much speed and graphics power as it could in exchange for low power demands. It also weaved whatever magic it could into the basic ARM design to focus the processor for the job in hand (running Apple mobile devices).

Because it integrates all these tasks: main processor, graphics and memory/memory controller, we call the A4 a System on Chip (SOC). It was code-named 'Hummingbird'.

So these were Apple's key requirements for A4:

  • Power demand must be low
  • Speed must be high
  • Optimized to run iOS, including SoC (graphics, memory).

Apple has its processor manufactured by Samsung. That company seems so impressed with the base ARM design used it went on to adopt that base processor for use in its own mobile products.

There's a very good account on the development of the A4 here. It points out that the chip produced benefited from lots of custom tweaks.

A caveat: Apple hasn't made a public statement on its A4 processor. iFixIt wrote in an April A4 teardown, "It's clear from both hardware and software that this is a single core processor, so it must be the ARM Cortex A8, and NOT the rumored multicore A9."

However, as noted below, the A9 can be created as a single core alternate. At present, industry consensus is that this is not the A9.


What about the A9?

So, what do we know about the basic ARM A9?

The ARM A9 will be capable of carrying multiple cores.

There's four officially described in ARM's reference designs, but an article at IT Portal confirms it is possible to tweak the basic design to deliver up to 16 cores.

"The Cortex-A9 MPCore processor provides the ability to extend peak performance to unprecedented levels while also supporting design flexibility and new features to further reduce and control the power consumption at the processor and system level."
Source: ARM.

I don't anticipate Apple will move beyond four. That's partially to maintain power demand. The A9 is available as a single core version too, giving you up to 2GHz speed for less power drain.

ARM's own website also tells us that,"Supporting the configuration of 16, 32 or 64KB four way associative L1 caches, with up to 8MB of L2 cache through the optional L2 cache controller, the scalable multicore processor and the single processor provide the broadest flexibility and are each suited to specific applications and markets."

Choices, choices

Should Apple opt for a single core model, it could field an A5 (as it is likely to call it, for continuity's sake) processor with a top speed of up to 2GHz (this will be a trade-off between power required and speed) with an 8MB L2 cache, also with built-in graphics and (chancing my arm) I'd anticipate double the memory.

"The Cortex-A9 power-optimized hard macro implementation delivers its peak performance of 4000 DMIPS while consuming less than 250mW per CPU when selected from typical silicon."

Should Apple go multi-core for the new processor, it could deliver a huge leap in performance speed, while still demanding little power.

You can even watch and make movies in HD on your iPhone -- that's a big testament to the multimedia power of the A4 chip.

That's essential of course because at some point even mobile devices will be handling 3D.

With this in mind, I've seen very few if any complaints at app performance (beyond instances in which an app is itself bad) on an iPad or iPhone 4. The only strong criticism I have come across is against the virtual multitasking in iOS 4.

Given this, I feel happy to speculate that the future ARM-based processor will also see Apple introduce us to a far less limited form of multi-tasking than the current iteration, as multi-core devices are intrinsically more capable of handling multiple concurrent tasks -- and demand little power to do so, (less than you'd expect.)

To exploit this, I'd anticipate next-generation iPads will field 512MB of memory, double its existing 256MB. The iPhone 4 holds double this.

Here's a link to ARM's own white paper regarding the Cortex-A9. It makes interesting reading.

Among other claims, ARM says the processors gets a near "25 percent processing power boost, even at same processor speed, from the use of a new instruction pipelining system." (MobileBurn).

The third way

Also worth noting is that the follow-up device to the A9, code-named 'Eagle' is also close to prime time, with Texas Instruments (TI) today announcing it has become the first licensee of that Cortex-A series processor core.

TI will produce processors for its Open Multimedia Application Platform device families using ARM's design. You'll find previous implementations of TI's ARM-based OMAP chips inside mobile devices from Nokia, inside the Motorola Droid, and so on.

That competitors will be leaping to a more recent processor design opens all kinds of new opportunities for Apple. Will it leapfrog A9 altogether, or is the company favoring a steadier approach to the base processor?

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