Wireless Intel Speedstep® Technology Power Manager; System Bus Frequency Selection - Intel PXA270 Optimization Manual

The Intel® PXA27x Processor Family power modes are shown in
Table 6-1. Power Modes and Typical Power Consumption Summary
Power Mode
Usage
Estimated
Power
(Measurement
Pending)
6.2.3 Wireless Intel Speedstep® Technology Power Manager
Most embedded operating systems do not offer the same power modes that the PXA27x processor
has available. It is typical for embedded operating systems to include only two or three power
states. The result is that either only a subset of the PXA27x processor power modes can be used in
a system or there must be additional software to interact with the OS to map one of the OS power
modes to multiple Intel PXA27x processor power modes.
As part of the Wireless Intel Speedstep® Technology Intel has developed a sophisticated software
product called the Wireless Intel Speedstep® Technology Power Manager that integrates with the
targeted embedded operating systems to allow for all PXA27x processor power modes used by the
OS. Through the use of sophisticated system profiling and control software the power manager
places the PXA27x processor in the lowest possible power state for the current system state,
without any additional OS or application interaction. The effect is to map, through the power
manager software, multiple PXA27x processor low-power modes to single OS power modes.
The power savings realized through the use of Wireless Intel Speedstep® Technology Power
Manager can be substantial and are an important part of the Wireless Intel Speedstep® Technology.
There are some additional considerations and additions required by applications in order to take
advantage of the power manager, but these additions were minimal.
For details about Wireless Intel Speedstep® Technology Power Manager software, please contact
your Intel representative.
6.2.4

System Bus Frequency Selection

The system bus runs at a frequency equal to either the run mode frequency or half the run mode
frequency, depending on whether fast-bus mode is selected. Fast-bus mode is discussed in
Section 6.2.4.1, "Fast-Bus
Intel® PXA27x Processor Family Optimization Guide
Normal Idle
LCD
controller
Used for must update
normal the display
operation of but there is
the core and temporarily
peripherals. no processor
computing
work.
Refer to the Intel® PXA27x Processor Family Electrical, Mechanical, and Thermal Specification
Mode".
Deep Idle Standby
LCD
controller
must update Used for a
the display short-term,
but there is low-power
temporarily "suspend
no processor state" when
computing there is no
work. All processor
controllers computing
connected to work and
the system peripherals
bus use are stopped.
13MHz
clock.
Power Optimization
Table 6-1.
Sleep Deep Sleep
Typically used for
a long-term low- Typically used for
power "off state" a long-term ultra
when there is no low-power "off
processor state" when the
computing work main battery is
and peripherals low.
are stopped.
Typically used The RTC and
when device is power manager
"switched off" but operate from a
internal SRAM deeply
and external discharged,
dynamic memory unregulated main
must be battery or backup
preserved. battery
6-3