ARM Unveils Big.Little, Low-Power Cortex-A7 Plan


ARM’s new Cortex-A7 is a key part of the company’s new Big.Little load-sharing mobile architecture

ARM Holdings, whose low-power chip designs dominate the booming smartphone and tablet markets, is unveiling its most energy-efficient chip yet, as well as a new processing model for its future system-on-a-chip designs.

ARM has announced the Cortex-A7 MPCore chip during an event in San Francisco, where officials called it the most energy-efficient application-class chip the company has ever developed. The Cortex-A7 offers five times the energy efficiency of the current Cortex-A8 – which is widely used in mainstream smartphones – and is a fifth of the size of its larger brethren, according to ARM officials.

Entry-level smartphones

The Cortex-A7 offers greater performance than the Cortex-A8, which officials said will bring a better overall user experience to low-end, entry-level smartphones that come in below $100 (£63). The 28-nanometer chip will start appearing in sub-$100 smartphones in 2013, and will offer the same level of performance that is found in current $500 (£317) high-end devices, according to officials.

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ARM does not make processors, but instead designs them and then licenses those designs to chip makers such as Qualcomm, Texas Instruments, Freescale Semiconductor, LG Electronics and Broadcom.

The Cortex-A7 announcement comes a day after ARM and manufacturing partner Taiwan Semiconductor Manufacturing (TSMC) had taped out the first 20-nanometre multicore Cortex-A15 chip, which the company first introduced a year ago. ARM officials have said they expect the Cortex-A15 to enable their designs to not only continue to dominate the market for smartphones and tablets, but also move up the ladder into PCs and low-power servers in the data centre.

The Cortex-A7 and Cortex-A15 also will be the key players in ARM’s new Big.Little architecture for higher-end devices. According to ARM officials, the Big.Little design is a way of addressing users’ seemingly conflicting demands for greater performance and longer battery life with lower power consumption.

The idea behind the architecture is to have both a Cortex-A7 and a Cortex-A15 reside on the same SoC. The lower-power Cortex-A7 would be used for basic tasks like social media, audio playback and calling, and for running the operating system. The Cortex-A15 would be used for the more compute intense workloads, such as navigation and gaming. Power management software would select the right processor for the right jobs in a fashion that would be transparent to the user.

ARM officials put the migration from one chip to another at 20 microseconds. ARM technology, such as AMBA 4 ACE Coherency Extensions, enables the switching of workloads between two processors and ensures full cache, I/O and chip-to-chip coherency between the two processors and across the system.

The result is highly optimised processing for each workload and increased energy savings.

Answering performance demands

“As smartphones and tablets continue to evolve into users’ primary compute device, consumers are demanding performance as well as the always-on, always-connected service they expect,” Mike Inglis, executive vice president of ARM’s Processor Division, said in a statement. “The challenge for our industry and the ARM ecosystem is how to deliver on this. The introduction of Cortex-A7 and Big.Little addresses this challenge and extends ARM’s technology leadership by setting a new standard for energy-efficient processors and redefining the traditional power and performance relationship.”

Freescale officials said they have licensed the Cortex-A7 chip design, and had previously licensed the Cortex-A15. The designs will be used for Freescale’s i.MX applications processors for such industries as embedded, automotive infotainment and smart mobile devices.

“As the market advances, there is an increasing need for low-power, higher-performance processing to deliver optimal user experiences across a broad range of markets,” Bernd Lienhard, vice president and general manager of Freescale’s Multimedia Applications Division, said in a statement. “ARM Cortex-A7 technology, coupled with Big.Little processing and Freescale’s multicore expertise, will enable us to innovate and deliver exciting new products to our customers.”

ARM is moving toward a full competitive scenario with chip giant Intel, which is looking to become a larger player in the mobile device arena. At the same time, ARM officials have been vocal about moving into such areas as PCs and low-power servers, which currently are dominated by Intel products.

The competition promises to ramp up next year, when not only will both companies be rolling out new products, but also Microsoft will release Windows 8, which will support both x86 and ARM architectures.

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