Let Sleeping CPUs Lie — S0ix
Summary
The article explains the evolution of laptop power management from SMI-based approaches to ACPI S0ix, detailing S0i1-3 states and the suspend-to-idle workflow. It describes how devices and CPUs are turned off and how the OS hints to firmware to enter S0ix, with AMD-specific PMFW/SMU considerations and USB4/GPU caveats. The piece also covers how FreeBSD is implementing suspend-to-idle and hibernate, and notes ongoing limitations and future work along with a technical reference link.