Sunday 9 August 2015

Is your Windows Laptop Working or Sleeping - G0 or G1?

Welcome to the World of the Hardware Software Interface on Windows. And how did we get here? How else, except through Device Manager.

Investigating your PC's Power Management Functions Via Device Manager

Anyone who has pulled up Device Manager on a laptop computer running Windows 98 or above, will have seen references to ACPI (Advanced Configuration Power Interface) which is the successor to APM. An example entry in Device Manager would be Computer defined as "ACPI x64 based PC".

The ACPI Specification and Involvement of Various Vendors

ACPI is a thousand page specification that allows Windows to communicate with the BIOS and instruct the BIOS to power down peripherals (the details of the specification are mainly of interest to Independent Hardware Vendors, or IHVs). 

ACPI is a joint effort between Hewlett Packard, Intel, Microsoft, Toshiba, and BIOS entrepreneur Phoenix Technologies Incorporated.

Four Basic States of a Component as Defined by ACPI

Working (G0), Sleeping (G1), Soft Off (G2) and Mechanical Off (G3). Within these global states are various sleep states.

Related Jargon like OSPM and AML

ACPI enables OSPM (Operating System-directed configuration and Power Management). AML is the machine language for ACPI.

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