Power Optimization; Introduction; Optimizations For Core Power; Code Optimization For Power Consumption - Intel PXA270 Optimization Manual

Power Optimization

6.1

Introduction

Intel® PXA27x Processor Family (PXA27x processor) includes many features designed for low
power consumption including: five power modes, 1.8 V memory support, and SDRAM auto power
down. This chapter provides a description of how to design applications for low-power
consumption and the tradeoffs between power consumption and performance.
The major topics covered in this section include considerations for reducing the power
consumption of the Intel XScale® core and memory. The power savings and performance tradeoffs
vary depending on the user's system configuration.
Refer to the Intel® PXA270 Processor Electrical, Mechanical, and Thermal Specification and the
Intel® PXA27x Processor Family Electrical, Mechanical, and Thermal Specification for detailed
information on power consumption.
6.2

Optimizations for Core Power

This section lists optimizations that may help to reduce power consumption consumed primarily by
the Intel XScale® core.
6.2.1

Code Optimization for Power Consumption

In most cases, optimizing the operating system (OS) or application for performance also optimizes
the code for power consumption. Increasing the caching efficiency and reducing the external
memory traffic are the keys to reducing power. Different assembly level- and high-level language-
optimization methods mentioned in previous chapters in this document should be implemented to
reduce power consumption.
6.2.2

Switching Modes for Saving Power

The PXA27x processor offers multiple power and frequency modes. This enables the system to
switch between modes, optimizing the system performance and power usage. The operating system
needs to develop a power management strategy based on the system's state at different points. In a
highly optimized system the OS can continuously profile the system activities and make decisions
based on this.
6.2.2.1

Normal Mode

All internal power domains and external power supplies are fully powered and functional. In this
mode, all clocks within the processor can be enabled.
Intel® PXA27x Processor Family Optimization Guide
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