XO-1/Software specification
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Power Management
Introduction and Related Material
Careful stewardship of battery power is critical.
This page is a work in process, collecting information related to power management on OLPC.
- Hardware Power Domains
- Power Management Software
- XO Power Management Tips and Tricks
- Misc. Papers on Energy Efficiency in Computing and Networking
In addition to effectively managing the power that is in the battery. The Battery and power page discusses many alternate power sources that could be used to supplement the existing charger.
Linux's Approach to Power Control
Linux is highly cross platform, running on just about all significant architectures, including many that are used for battery powered embedded systems. The infrastructure for power management has therefore become quite sophisticated over the last years, though it is still maturing. This means that the facilities are general, and not tied to any particular architecture. The generation one OLPC system, being from the x86 part of the world, is therefore similar and fundamentally different from other x86 based systems, for reasons that will become clear in the discussion below.
Linux is not dependent on ACPI or the older APM power management systems, which are x86 specific. As such, Linux's design has always done its power control in the operating system, and ACPI and the like are considered "platform dependent".
OLPC's Innovations
The DCON chip lets us take over refresh of our very low power flat panel and therefore completely power off the processor board. Given our flat panel is usable in gray scale mode at .1 watt, you can see that the leakage currents and power supply power consumption of the system board can dominate power consumption easily.
We are also able to leave the Marvell wireless module to operate independently, forwarding packets in the mesh while possibly everything else is powered down.