Advanced Configuration and Power Interfaces
The term English Advanced Configuration and Power Interfaces (ACPI) (which means advanced interface of configuration and energy management ) indicates a standard which Co-was developed by Hewlett Packard, Intel, Microsoft, Phoenix Technologies and Toshiba which is very largely widespread in the modern personal computers.
The goal of this standard is to reduce the consumption of energy of a computer by putting not under tension certain elements (such as the readers CD-ROM, the Hard drives, the screen…)
For that, an interface was specified which allows the Operating system to send signals to these various material peripherals (it is necessary that these peripherals also support the ACPI). This interface also makes it possible the material to send signals to the operating system, for example when the user presses on the button of startup on the keyboard or that the Modem receives a call.
This standard is used as well on the laptops as on the recent desktop machines. The very last specification which dates from the 10 October 2006 carries the version 3.0b.
Presentation
The most important point of this specification is that it is the Operating system which is responsible for the management of the food of the components of the computer, it is a big change compared to the preceding standards as APM where BIOS was the software responsible for the management of food.Another important component is that the optimized management of the food (since always vital for the autonomy of the Laptops) is now a standard which is implemented in other computer materials (until the waiters) and makes it possible to optimize their electricity consumption according to the load.
ACPI functions only with the materials planned for and requires on behalf of the manufacturers the management of a specific data-processing language (AML) for the management of the events.
The first version of Microsoft Windows to have managed ACPI was Windows 98. The first version of FreeBSD to have managed ACPI was version 5.0. Linux, NetBSD and OpenBSD has a whole today a management at least partial of ACPI.
Concepts
The standard defines the states of the entire system (G0… G3 and S0… S5) and also of the peripherals (D0… D3) and of the processors (C0… C3). The rule being that the state x0 (G0/S0, D0 or C0) corresponds to a servicing equipment and consuming energy and the following states with equipment requiring more and more operations to be given in state x0.The standard also defines the management of the performance levels (P0…), of the configuration of the peripherals and discovered PnP, the events of the system, the energy of the batteries, the thermal zones…
Total states / Sleep states (states of the system and sleep)
These states are classified by the standard on the basis of that or the computer is completely in service and going towards situations where the computer takes more and more a long time at becoming usable.- G0/S0 in service: the computer is entirely in service.
- G1 sleep: no processor carries out instruction, however the user did not require a complete stopping of the computer. To leave this state the operating system does not have to re-execute all the sequence of starting but takes again its operation starting from the state where it was before this stop. This state is subdivided in several under states.
- G1/S1 power one suspends : no processor carries out instruction but no context of execution is lost and the computer will be able to leave this state very quickly. In this state, the food is always in service but the discs are stopped (as in all the following states).
- G1/S2 standby : state of major sleep, the processors will have to be re-initialized with the alarm clock, the operating system will have to then restore the various contexts of execution. This state is documented in seldom implemented specification ACPI but.
- G1/S3 suspends to RAM : in this state the computer extinguishes the principal food, but the state of the main memory is maintained by employing a permanent food (called 5VSB) thus it will restore its state more quickly than in G1/S4.
- G1/S4 suspends to disk : the state of the system (in particular contents of the memory and contexts of execution of the processors) was safeguarded (generally in a file of hibernation on an hard drive). The whole of the components of the computer is without food. With its start-up the operating system will have to reload this file of hibernation and will restore the state of the computer then.
- G2/S5 controlled stop ( software off ): electricity consumption is most reduced possible and no current state of the computer was safeguarded (the user asked the system to stop completely) however the food although stopped is always connected to an electric source and provides the permanent food 5VSB (moreover the keyboard remains often fed because the pressure of a key makes it possible to start again). During the start-up the operating system will have to carry out all the sequence of starting before being available.
- mechanical G3 stop: in this state a mechanical switch was operation and only a human operation can make it possible to start the computer. One could believe that in this state plus any component is not fed, but it is inexact : in a PC for example a pile (generally with the lithium) still feeds a small circuit CMOS and makes it possible to maintain some information of configuration as well as a clock.
Device states (states of the peripherals)
These states are classified more consuming energy (peripheral in the course of use or D0) until the least consuming (extinct peripheral or D3).A peripheral in D3 state will need a cycle of initialization supplements before becoming again usable (it can for example require the loading of a Micrologiciel carried out by its pilot before being used).
CPU states (states of the processors)
The standard also defines four energy levels for the processors graduated according to energy consumption. In C0 state, the processor is in service and carries out instructions then in the following states it does not carry out more instruction and sees its electricity consumption reduced to the price of one return to increasingly long the C0 state.The C1 state can be obtained on a processor of the family X86 while making him carry out instruction HALT. Starting from the C2 state, the clock does not need even more him to be provided. In the C3 state, the processor can be extinct electrically and will have to be re-initialized before carrying out instructions again.
Tables ACPI
These tables are used by the operating system to obtain information on the material which it controls.RSDP (Root System Description To point)
RSDT (Root System Description Counts)
DSDT (Differentiated System Description Counts)
XSDT (Extended System Description Counts)
FADT (Fixed ACPI Description Counts)
FACS (Firmware ACPI Control Structure)
SBST (Smart Battery Counts)
ECDT (Embedded Controller Boot Resources Counts)
MADT (Multiple APIC Description Counts)
SRAT (System Resource Affinity Counts)
SLIT (System Locality Distance Information Counts)
SLIC (Software Licensing Description Counts)
SSDT (Secondary System Descriptor Counts)
THRM (Thermal CPU)
See too
- Advanced Power Management
- Put in day before
External bonds
- Official site
- French Adaptation of handy guide ACPI