ARM unveils Cortex-A7 chip for smartphones

ARM Holdings has introduced the Cortex-A7, a new microprocessor design that will be used in sub-US$100 smartphones, as well as in high-end smartphones alongside the more powerful Cortex-A15.

ARM designs the chips used in most of the world’s smartphones and tablets, including Apple’s iPad and iPhone. The A7 will be its most energy-efficient chip design to date, ARM said. Samples are due next year, and the A7 will appear in entry-level smartphones by 2013, ARM said.

But the A7 will also be used in high-end smartphones alongside the upcoming Cortex-A15, as part of a new power-saving architecture that ARM calls big.Little. With that design, high-performance tasks such as gaming and video playback are performed on the more powerful A15 chip, while tasks that require less power, such as posting a status update or making a phone call, are assigned to the A7 to conserve power, ARM said.

By combining two types of core on the same chip, and assigning different applications to each depending on their requirements, ARM said it can resolve the conflict between the need for both higher performance and longer battery life. It will reduce power consumption by 70% for many common tasks, compared to mainstream smartphones today, it said.

It’s a new approach for ARM but not an entirely new one for the industry.

For example, Nvidia disclosed recently that its quad-core chip for tablets and smartphones, code-named Kal-El, actually has a fifth core for performing tasks that require less processing power. It’s the same in principle as big.Little, except Nvidia is using a Cortex-A9 design for all five cores, and it developed its own technology for keeping the cores in synch.

The A7 will be manufactured on a 28-nanometer process, ARM said. The more advanced process, combined with architectural improvements, makes it one-fifth the size, with one-fifth the power consumption, compared with today’s Cortex-A8 processor, ARM said. But the A7 will still give a 50% performance boost compared to the A8, according to ARM.

It will have a die size of less than 0.5 square millimeters and draw less than 500 milliwatts of power, according to Nandan Nayampally, director of marketing for the ARM processor division.

“Other chips, such as Intel’s Core i7 laptop processors, ramp down the clock speed or disable cores to reduce power consumption. But there’s a limit to how much power can be saved using that technique,” said Nathan Brookwood, principal analyst at Insight64.

“There’s a dynamic range for which you have to optimise the processor design, and there’s a limit to how much you can power it down and still have it run at all. That’s why Intel had to go off and design the Atom processor very differently from the i3, i5 and i7 series,” he said.

ARM’s approach has “a lot of promise,” Brookwood said, “especially for devices where battery life is important, and where you’re running applications with very different power requirements.”

The A7 and the A15 will have “identical” feature sets, so software applications will run on both cores without modification. ARM designed a policy manager to determine on which core the application should run.

ARM has multiple processor designs and it’s getting hard to keep them all straight. The Cortex-A8, released in 2009, has one core and powers most of the smartphones in use today. The Cortex-A9, a more powerful design with up to four cores, came out this year and is being used in most new smartphones. The Cortex A-15, due out next year, will be more powerful still, and is aimed at servers and routers as well as phones and tablets.

ARM showed a sample A-15 processor, with two cores, running Android on a test board here at the event. It wasn’t much to look at but was intended to show that ARM is on track with its development.

The A7 emphasises low power over high performance, which is why ARM went backward with its version numbers, instead of calling it the A-10. It’s suitable for tasks such as music playback and casual gaming. The A15 cores will run rich Web applications, high-def games and augmented reality applications, ARM said.

ARM’s designs are licensed and manufactured by companies such as Texas Instruments, Broadcom and Freescale, who were all at its event along with Nokia, Samsung, Sprint and others. The chip makers are expected to produce the first A7 parts next year, so smartphone makers should have them in devices soon after that.

It may take chip makers a bit longer to implement the combined A7-A15 design, but that too could appear in smartphones by 2013, ARM said.

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