In System-on-Chip, or SoC, circles, smaller is better. The smaller we can make a given processor, modem and other chips, the less voltage is needed to drive the unit. Power consumption for a silicon chip is proportional to the square of the voltage used; in other words, a small reduction in voltage can have a big reduction in power consumed. There are many advantages of reducing the power consumed by a processor core; one is that it’s kinder to the battery, another is that it reduces the heat output by the processor, which means we can either use thinner chassis for our devices or run them harder for longer and maintain the same performance. Ultimately, the cooler the chips are, the better. And ARM’s newly announced Cortex-A72 offers a reduction in die size to 16nm. Most processors used in devices built over the last 18 months use a 28nm die size, although Samsung have pushed into the 20nm zone with the Galaxy Alpha and some Note 4 models, plus the Snapdragon 810 uses 20nm die size processor cores.
Combining this reduced die size with the usual refinements that we see from processors, when ARM compared the Cortex-A15 processor core (which is used in say the Nvidia Tegra K1-32 processor, which we find in the Shield Tablet) the A72 promises three and a half times the performance. The Cortex-A72, which is set to arrive next year, is also significantly more powerful than the current champion core, the Cortex-A57, which is being used as part of the Qualcomm Snapdragon 810 processor. By significant, what does that mean? Almost twice as powerful, when ARM compares the 16nm A72 with a 20nm A57.
We’ve seen ten manufacturers licensing the A72 core including the mainstream processor manufacturers, MediaTek, Samsung and Qualcomm, plus other Chinese manufacturers such as Rockchip and HiSilicon. And we’re expecting the Cortex-A72 to be paired up with the existing Cortex-A53, which is the lower performance, high-efficiency part of the big.LITTLE processor cores. The reason why SoCs combine lower performance, high-efficiency processor cores with less efficient, but more powerful cores, is that for light workloads, the high-performance processor cores are inefficient whereas the less powerful processor cores use less power. There are many complex systems designed to integrate the two sides of the big.LITTLE equation and ARM will be introducing improvements with the Cortex-A72 that will further refine this process. It’s also in ARM’s interest for SoCs to use more cores, as they license their intellectual property based on the number of cores in a given device…
It’s an exciting time to be watching the SoC wars. ARM’s ongoing development will help reduce battery consumption and increase device performance, but their business model means that multiple SoC manufacturers can use this technology and so compete on price and other features. 2015’s processor lineup is already exciting, we’ve great things to look forward to!