Full Form of APM:
Advanced Power Management
APM Full Form is Advanced Power Management. APM is an application programming interface developed jointly by Microsoft and Intel to achieve power management. It basically enables an OS (Operating System) that is running an IBM compatible PC (Personal Computer) to interact with (or) to work with any Basic Input/Output System (BIOS) to achieve this power management. The APM is designed to control the power usage of the system. Until the system is brought into suspend state.
Approach used by advanced power management:
A layered approach is used to manage the device. The application included device driver talk to OS specific APM driver. APM aware BIOS control the hardware. The driver communicates with this aware BIOS and power management is sent to APM driver from Bios. The driver sends information by the function call. APM driver works as an intermediator between BIOS and operating system.
States of power control:
Two states of power control include; (1) On the basis of device activity, APM BIOS manages power in the background. By OEM it supplies APM BIOS and it is hardware platform specific. (2) By calling a function to the APM software interface APM driver manages power.
There are 5 system power states-
States are created on the basis of latency needed to the system to power up to working state.
- Full On: Higher power consumption in this state. No power management is done in this state.
- APM Enabled: No power management is done in some unused device but the system is doing work in this state.
- APM Standby: System is inactive for a short period and comes into this state.
- APM Suspend: Inactive for a long period and system come into this state. Taking too much time to come into Enable state from the suspend state.
- Off: CPU clock is stopped in this state.