ACPI-Advanced Configuration and Power Interface

ACPI indicates the Advanced Configuration and power management interface ).

 

For Windows 2000, ACPI defines a new working interface between windows, bios, and system hardware. These new interfaces include mechanisms that allow Windows 2000 to control power management and device configuration.

Advanced Configuration and Power Interface (ACPI) was jointly developed by Intel, Microsoft, and toshba in 1997 to provide all the power management interfaces for operating system applications. In August 2000, The ACPI 2.0 specification was launched. In September 2004, The ACPI 3.0 specification was launched. In June 16, 2009, The ACPI 4.0 specification was released. December
6 and 2011 are 5.0 specifications.

As the most widely recognized part of the standard, power management has undergone many improvements.

Previously, the advanced power management model (APM) allocated almost all power management to BIOS control, which greatly limits the operating system's ability to control power consumption.

Currently, the power management feature of ACPI previously only applies from portable computers (such as laptop computers) to desktop computers, workstations and servers. For example, the system may enter a very low power consumption state. These are "Sleep" and "Sleep" settings available on most desktop computers. Sleep and sleep statuses can be awakened by moving the mouse, pressing the keyboard, and receiving a message (if connected to a LAN) or a major system error from another computer.

Now, if ACPI is implemented in bios and other system hardware, it can be called (triggered) by the operating system ).

 

ACPI provides the following functions:

System Power Management)

Device Power Management)

Processor power management)

Device and processor performance management)

Configuration/Plug and Play)

System Event)

Battery Management)

Thermal Management)

Embedded Controller)

SMBus Controller)

 

Windows 98 is the first Microsoft operating system that supports ACPI. FreeBSD V5.0 is the first UNIX operating system that supports ACPI. Linux, NetBSD, and OpenBSD both have at least some ACPI support.

 

ACPI supports three power-saving modes

1. (suspend is suspended) the display is automatically powered off, but the host is powered on. At this time, you can press any key to restore the original state.

2. (save to Ram or suspend to ram is suspended to the memory) The system stores the current information in the memory. Only the memory and other key components are powered on, and the computer is in a high power-saving state, after pressing any key, the computer quickly restores the Information read from the memory to its original state.

3. (save to disk or suspend to disk is suspended to the hard disk) the computer will automatically shut down and store the current data on the hard disk before shutdown. The computer will not need to start the system the next time you press the key to start the system, read data directly from the hard disk to restore the original state.

 

ACPI provides the following functions:

1. You can enable the peripherals to switch at a specified time;

2. Users who use laptops can specify that the computer enters the low-power state at low voltage to ensure that important applications run properly;

3. The operating system can reduce the clock frequency when the application requires less time;

4. The operating system can allocate energy to peripherals and boards based on their specific needs;

5. When no one uses a computer, the computer can enter sleep state, but some communication devices can be enabled;

6. The plug-and-play device can be controlled by ACPI during insertion.

 

However, ACPI is the same as other power management methods. to enjoy these features, you must have software and hardware support. In terms of software, Windows 98 supports (but not all, STD is disabled, and parameters are forced to be enabled for setup.exe, but there are many bugs). Windows 2000 provides comprehensive support for ACPI; hardware is troublesome, in addition to supporting ACPI for peripherals such as the motherboard, video card, and nic, the power supply of the chassis is also required. When the power supply provides a 5 V voltage to the motherboard, it must also make the current stable at more than 720 mA, so that it can achieve computer "Sleep" and "wake up ".

 

There are six ACPI statuses

They are S0 to S5, and their meanings are:

S0 -- in fact, this is our normal working state. All devices are fully open, and the power consumption generally exceeds 80 W;

S1 -- also known as pos (power on suspend). In this case, in addition to disabling the CPU through the CPU clock controller, other components still work normally, and the power consumption is generally below 30 W; (In fact, some CPU cooling software uses this working principle)

S2-the CPU is stopped and the bus clock is disabled, but other devices are still running;

S3 -- this is the familiar STR (suspend to ram). At this time, the power consumption cannot exceed 10 W;

S4 -- also known as STD (suspend to disk), when the system's main power is off, the hard disk stores data information before S4, so S4 is more power-saving than S3.

S5 -- this state is the most simple, that is, all the devices, including the power supply, are shut down, and the power consumption is 0.

 

What we use most frequently is the S3 status, that is, the suspend to Ram (suspended to memory) status, STR for short. As the name suggests, STR stores all the operating status data before the system enters STR into the memory. In the STR state, the power supply continues to power the most necessary devices, such as memory, to ensure that data is not lost, while other devices are in the off state, and the power consumption of the system is extremely low. Once we press the power button (host power switch), the system will be awakened and the data will be immediately read from the memory and restored to the working status before Str. Memory read/write speed is extremely fast, so we feel that it takes only a few seconds to enter and exit the STR state; and S4 status, that is, STD (suspended to the hard disk) the principle is the same as that of STR, except that the data is stored on the hard disk. Because the read/write speed of the hard disk is much slower than the memory, it is not as fast as Str. The advantage of STD is that it can be implemented only through software. For example, Windows 2000 can implement STD on hardware that does not support Str.

 

ACPI mode FAQs

Computer sleep

This is mainly because the hardware does not support ACPI well. At this time, you should first read the motherboard and other hardware instructions to see if they fully support ACPI. Sometimes the USWC uncacheable speculative write combining mode of the video card is set in the BIOS. You can solve the problem by returning to the UC uncacheable mode.

STD mode failure

STD is a power-saving advanced application called "suspend to disk" (STD is the function to sleep to the hard disk. After saving the current system status to the hard disk, the hard disk stops rotating, the system enters the low-power state. When the system is restarted, the system will skip self-check and directly restore the original system state from the hard disk, instead of the default state of the normal system, thus shortening the boot time .) This mode may cause problems due to the compatibility of the hard disk file format. You can solve the problem by refreshing the BIOS.