0.5mm2 ARM chip offers 5X energy efficiency, jacks up performance

big.Little extends Moore's Law

ARM's new energy efficient Cortex-A7 processor will bring computing to a billion more people, its CEO claimed yesterday. Which may or not be a good thing.

For the rest of us, harnessed to one of their most powerful processors, the A15, it will also form the basis for a System on a Chip that will make two processors work as one and enable additional power gains and energy savings.

ARM CEO Warren East claimed on Wednesday in London that at both five times more energy efficient and twice as powerful as current mainstream smartphone chips, the A7 will enable the manufacture of $100 smartphones designed for the developing world, when it hits the market around 2013. Combined with the A15, it allows what he called "big.LITTLE processing" to address one of the key problems in mobile technology – the demand for greater power with less energy consumption.

It achieves this feat by linking two processors together so they work as one. It pulls together the energy-efficient A7 – which is built on a 28nm process, and measures in at under 0.5mm2 – and the powerful A15 and allocates different tasks to each depending on what's needed.

"We take a very efficient processor like the A7 and very powerful processor like the A15 and deploy the right processor for right task at the right time," East said.

Low intensity tasks such as playing music, sending texts and making phone calls will use the A7, while the A15 will kick in when needed to boost power (up to 5x the oomph that is available in this year's smartphones) on high intensity tasks like gaming, or navigation.

The switch will, ARM says, be as quick as opening a webpage – which will call on the A15 – and then scrolling the loaded page which will flick you back to the A7.

This switching between processors is almost completely invisible to the software, said East, appearing to apps and the OS as if it were running on a single processor. It will be backwards compatible with all ARM-friendly software.

ARM say demos with the new chip showed that it gave a 60 per cent energy savings on casual gaming, and a 70 per cent savings on simple tasks like checking email and other general OS/UI activity.

ARM already have eight public partners for the licence, including mobile giants Samsung, LG and QNX. The other partners are Broadcom, Compal, Freescale, Linaro, OK Labs, Redbend, ST-Ericsson and Texas Instruments. The A7 will be shipping at the end of 2012.

Chips based on ARM cores are already the most energy-efficient in the market – hence their dominance in the mobile arena, and the basis for ARM's soaring profit sheet.

However, the main energy cost on any smartphone will almost always be the display, which consumes around 80 per cent to 90 per cent of a handset's available power depending on usage, meaning that energy savings on chips, while beneficial, will have minimal battery impact from a consumer perspective. ARM will be reliant on its hardware and software partners to come up with answers to the battery too.

A Samsung representative at the event said:

We believe that our customers would like to enjoy more PC-like features, higher display resolution, rich graphics ... at same time they want the same or better battery experience which is actually very challenging for us. We will need not only traditional ideas but also innovative ideas like the big.Little processor.

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