Difference Between ACPI and APM

ACPI (Advanced Configuration and Power Interface) and APM (Advanced Power Management) are both power management systems used in computers to control power consumption and maximize energy efficiency.

ACPI is designed to handle power management tasks other than basic on/off functions, such as managing system resources, devices, and processor performance. APM is an older and simpler system that provides fundamental power management functions.

Read this article to find out more about ACPI and APM and how they are different from each other.

What is ACPI?

The ACPI (Advanced Configuration and Power Interface) standard was created by Intel, Microsoft, and Toshiba. It gives the operating system an advanced and flexible technique to control the power consumption of a computer's hardware components

ACPI is designed to perform power management tasks other than simple on/off functions. It specifies a collection of interfaces and protocols that allow the operating system to handle system resources, devices, and processor performance. This means that ACPI gives the operating system more power management control than previous power management systems such as APM.

ACPI specifies a number of power states in which a computer's hardware components can be. The following are some of the states −

• G0 (S0) − Fully On State

• G1 − Sleep State

• G2 − Soft Off State

• G3 − Mechanical Off State

These power states allow the system to conserve power when not in use while still responding quickly when required.

ACPI also allows the operating system to communicate with the BIOS (Basic Input/Output System) in order to configure power management settings. This provides the operating system with more power management control than earlier power management systems.

What is APM?

APM (Advanced Power Management) is an older power control system that was introduced in the early 1990s. It is a simpler system than ACPI and offers basic computer power management functions.

APM provides a way for the operating system to control the power state of the computer, monitor battery status, and control the behaviour of the computer when the battery is low. It defines several power states that a computer's hardware components can be in, including −

• On

• Standby

• Suspend

• Off

These power states allow the system to conserve power when not in use while still responding quickly when required.

APM's ability to manage battery usage is another important feature. It allows the operating system to monitor the battery level and determine how much battery life is left. It also allows the operating system to regulate the computer's behaviour when the battery is low, such as switching to a power-saving mode automatically.

The limitations of APM are that it is a proprietary system, so it is restricted to specific manufacturers and operating systems. This can make using APM on newer hardware or operating systems difficult.

APM is still used in some legacy systems, despite its disadvantages. It offers a basic collection of power management functions that can assist in power conservation when the system is not in use. Newer power management systems, such as ACPI, offer more advanced and flexible ways to manage power consumption and are more commonly used in modern computers.

Difference between ACPI and APM

The following table highlights the major differences between ACPI and APM −

Characteristics	ACPI	APM
Open Standard	ACPI is an open standard.	APM is a proprietary system.
Stands for	Advanced Configuration and Power Interface (ACPI)	Advanced Power Management (APM)
Age	A Newer Power Management System	Older Power Management System
Hardware and Software Support	It supports a wide range of hardware and software platforms.	It is limited to certain manufacturers and operating systems.
Power States	ACPI defines several power states such as fully on, sleep, soft off, and mechanical off.	APM defines the several power states such as power on, standby, suspend, and off.
Compatibility	It has compatibility with newer hardware.	It has compatibility with legacy devices.
Dependent	ACPI is dependent on BIOS.	APM is dependent on the operating system.
Invented By	It was invented by Microsoft and Intel.	It was invented by Toshiba, Intel, and Microsoft.

Conclusion

In conclusion, ACPI and APM are both power management systems used in computers, but they differ in several aspects. ACPI is a more advanced and sophisticated system that provides greater control and more sophisticated power management functions, whereas APM is an older and simpler system that provides fundamental power management functions.

Furthermore, ACPI is an open standard, whereas APM is a proprietary system, which means that ACPI is supported by a wider range of hardware and software platforms. While APM is still used in some legacy systems, ACPI is the more commonly used and modern power management technology in modern computers.