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ARM unveils Cortex-A7, 'big.LITTLE' design

HardwareNews
, 20 Oct 2011News

British chip design giant ARM has officially unveiled its Cortex-A7 MPCore processor, which it claims is the most energy efficient design yet, along with a concept it calls 'big.LITTLE processing.'

The Cortex-A7, designed for use as a secondary processor or in low-end smartphone devices, takes up just one-fifth the footprint of the Cortex-A8 chip while offering five times the energy efficiency, the company claims.

Measuring around 0.45mm² in a single-core version, the teeny-tiny chip is built on a 28nm process size and offers surprisingly powerful performance and the same feature set as ARM's latest Cortex-A15 'Eagle' design.

Running at 1GHz yet drawing the same power as the Cortex-A5 chip, the Cortex-A7 packs an FPU, NEON multimedia acceleration, 32KB of L1 cache, an integrated L2 cache, improvements to the branch prediction engine, a 64b Load Store path and 256-entry TLB - both double that of the Cortex-A5 - and 128b AMBA 4 buses to improve bandwidth in multi-processor implementations.

The Cortex-A7 is available in single- to quad-core configurations, with ARM claiming that the chip will allow sub-$100 smartphones in 2013 that offer the same processing performance of today's high-end $500 smartphones.

The launch of the Cortex-A7 MPCore was joined by ARM's announcement of the 'big.LITTLE' architecture, which bears an uncanny resemblance to the 'companion core' concept seen in Nvidia's upcoming Tegra 3 'Kal-El' chip.

In a 'big.LITTLE' implementation, the low-power Cortex-A7 is used as a secondary processor on the same system-on-chip layout as a more powerful chip - namely the Cortex-A15.

The idea is to allow the low-power Cortex-A7 chip to run the operating system and background tasks, allowing the more power-hungry main cores to power down completely until required by a more demanding application - with the switchover taking as little as 20 microseconds.

"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. The challenge for our industry and the ARM ecosystem is how to deliver on this,” explains Mike Inglis, executive vice resident of the processor division at ARM.

"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."

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