ACPI power management
ACPI compliant operating systems like Windows implement system power states S0-S5:
Notes:
- The wakeup latency should be <2 seconds from S1, and increasingly more for S2-S4.
- The computer never transitions directly between states S1 and S4 since they require code execution that is not possible when the CPU is turned off (Windows Internals 7th ed. part 1, p.592). All transitions therefore goes through S0.
- This figure does not cover device-specific power management, such as dimming the display or stopping the HDD after X minutes of inactivity.
Docs:
- Driver: System Power States
- Win32: System power states
- System Sleeping States - mentions system wakeup latency requirements
Modern standby was introduced in Win10 to reduce wakeup latencies. Not sure how exactly it related to ACPI modes.
Docs:
- HW: What is Modern Standby
- Prepare software for modern standby
- Prepare hardware for modern standby
- Modern Standby States
PnP compatible devices have power states D0-D3:
HW vendors expose which of the D0-D3 states are supported for a given device, as well as the respective wakeup latencies.
Docs:
- Device Power States
- Device Low-Power States
- ACPI Device Class Specifications - mentions HW wakeup latency requirements
Device drivers are responsible for mapping system power states S0-S5 to associated device power states.
For a webcam:
For a network card:
For a sound card:
For a monitor:
