Power management is a extensive topic, some basic elements need to understood be we go deeper.
In Linux if we click on shutdown 4 options will be provided
1. Shutdown
2. Standby
3. Suspend
4. Hibernate
Standby mode: LCD and display back light are turned off, CPU clock speed is reduced. Power saving will be less but latency will be less. Here latency refers to the time taken to resume.
Suspend mode: Suspend to RAM, CPU in sleep state which means power is turned off in most of the devices and parts of CPU. But DRAM puts itself in self refresh mode to preserve the machine state. CPU will be wake up from sleep state by some preprogrammed event.
Hibernate: Suspend to disk, is like powering down a system by retaining its state into disk, active pages in RAM will be moved to disk (persistent storage), power to RAM is also turned off. Hibernate needs a swap partition or swap file space to swap the RAM contents. Latency will be more.
In Linux if we click on shutdown 4 options will be provided
1. Shutdown
2. Standby
3. Suspend
4. Hibernate
Standby mode: LCD and display back light are turned off, CPU clock speed is reduced. Power saving will be less but latency will be less. Here latency refers to the time taken to resume.
Suspend mode: Suspend to RAM, CPU in sleep state which means power is turned off in most of the devices and parts of CPU. But DRAM puts itself in self refresh mode to preserve the machine state. CPU will be wake up from sleep state by some preprogrammed event.
Hibernate: Suspend to disk, is like powering down a system by retaining its state into disk, active pages in RAM will be moved to disk (persistent storage), power to RAM is also turned off. Hibernate needs a swap partition or swap file space to swap the RAM contents. Latency will be more.
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