Answer to Question #162929 in Assembler for Muhammad Ahsan Sohail

Question

A smartwatch is a very useful device developed by several companies these days including Apple, Samsung, Motorola and several others. It has a touch screen interface providing features like GPS tracking, heart rate and sleep monitoring etc. with power efficient batteries. The ARM Cortex processors are used in smartwatches providing several benefits.

 

Suppose we have to choose between ARM Cortex-A or Cortex-M series architecture for our next generation smartwatch. Which one would you select between the two and why? Support your selection of either architecture with solid reasoning considering memory management, cost, performance and chip size.

Answer 1

Both.

    The biggest design considerations for wearables are energy efficiency, battery life, and heat. Consumers don’t want to have to charge up their devices every couple of days, let alone every few hours. Therefore, manufacturers must reduce the power consumption of their processors to help developers create devices that can last a week on a single charge.

    ARM Cortex-M designed for low-cost, low-power microcontroller situations. The Cortex-M have sufficient performance. It based on the ARM v7-M architecture, support the ARM Thumb2 instruction set, and comes with digital signal processing capabilities and an optional floating point block for math calculations.

    The most basic smart watches can get away with a simple MCU but the more features it has, the higher the requirements will be in terms of processing power.

    The other option is to use entry-level Cortex-A chips .The Cortex-A’s modular design allows developers to target other use cases for wearables. Some components, such as the CPU’s memory caches, can be scaled down, and a few can be omitted completely to save on power and space. Low-power fabrication techniques can also lead to greater efficiency, at the expense of peak performance, which is not required in a wearable setting.

    Cortex-A chips that can be used in wearable devices are not necessarily as powerful as the Cortex-A chips used in smartphones or tablets. This is a necessary compromise.

   The right balance needs to be found: Cortex-M chips for simple smartwatches and a combination of Cortex-A and -M cores for higher-end products.

    For basic devices, which typically require extended battery life and little user input, the Cortex-M series is perfect for the job, due to its low power requirements and efficient instruction set. However, devices that are required to work with more advanced user inputs and richer software would benefit from the optimized Cortex-A design, as it offers a better balance of performance and power consumption, and the full ARM 32-bit instruction set found in smartphones.