We have come a very long way in Mobile Technology! The very early Mobile Phones were capable of only processing voice, then came the mobile phones that had both voice and data capabilities. Very quickly we moved through the era of smart-phones and today we have super-phones that are capable of processing very complex tasks such as voice & gesture controls, seamless content delivery, HD audio/video, gaming with highly advanced user interface, multitasking capabilities & 24X7 internet connectivity.

In order for mobile phones to process such complex functionalities, there is a need for very fast Central Processing Unit (CPU) for your phones. CPU technology has evolved at a very fast pace, so today we have very high performance CPU available for mobile phones but the challenge remains that these CPU should be power efficient; means they should give maximum performance while operating on small mobile power (mobile batteries). Also the fact remains that the battery technology has not evolved at a same rate as the CPU technology, hence this is one reason why the size of your mobile handset & the size of your mobile battery is almost the same! Thus, the future mobile phones require high speed CPUs with very low power consumption so that they can operate on small mobile battery and give maximum power efficiency.

ARM big.LITTLE Technology is designed for future generation mobile phones with CPUs featuring a heterogeneous processor architecture that uses two types of processors - "Little Processor" designed to give maximum power efficiency and "Big Processor" designed to give maximum CPU performance. Both processors are coherent and share the same instruction set (ISA). With this technology, any computing task or function can be dynamically allocated to the big or little processor core depending upon the processing requirement of the task.

The first big.LITTLE processing pair consists of the ARM Cortex®-A15 (big) & Cortex-A7 (LITTLE) processors. Since both processors have same instruction set architecture (ISA), same programs or functions can run on both processors in consistent manner. Differences in the internal micro architecture of the both processors allow them to provide the different power and performance characteristics and this is the fundamental concept. Now different tasks or functions have different and constantly changing performance and power requirements. In a typical system, most tasks can be carried out perfectly by LITTLE processor. If the performance requirement for a task goes above, big processor turns-on to service that task. In this way performance hungry tasks can then be migrated to big processor. Thereafter, when the performance requirement reduces, tasks can be re-allocated to LITTLE processor and big processor switches off there by quickly reducing power consumption. The ARM big.LITTLEb technology has been well qualified with Android. Also 98% of all mobile phones use one or more of ARM processors in them. Apple use ARM processors for its iPhones.

Our world today is dominated by mobile phones, and the mobile processor (CPU) technology is evolving or changing very fast owing to the pressing requirements of the market as discussed above. Mobile CPU Architecture are different from Computer CPU Architecture in so many different ways as Mobile CPUs run on small portable batteries, have communication functionalities GSM, GPS and other different types of sensor interfacing like Bluetooth, Near Field communication, Temperature, Altitude, Medical Sensors etc. It is estimated that by 2017 over 2.8 billion people will own a smart-phone. This is the reason some of the global multinational companies like ARM, QUALCOMM, Imagination Technologies are focusing on building advanced mobile CPUs.

By Sagar Juneja, Research Associate, Chitkara University.

References

www.arm.com