The CPU has several mechanisms to control temperature and consumption. In this tutorial we will show you how P-States and C-States work , in addition to explaining what they are. This way, you will have a clearer idea of everything about your team’s energy management. Before moving on to the P-States and C-States, it is first necessary to introduce what APM (Advanc Power Management) is , a programming interface or API that allowe the operating system to control power management on IBM PCs and compatibles. This system was along with the BIOS on these computers. This APM system was jointly by Intel and Microsoft , and was made public in It was a step forward. In order to manage power, especially in laptops where this was even more important.
What is ACPI?
APM became obsolete and was replaced by. ACPI (Advanced Configuration and Power Interface) , or power management interface. This new system goes beyond APM, with new functions to allow more comprehensive and efficient control of energy. Unlike the previous one, this system not only works for x. PCs, but has also been implement for other architectures such as ARM, etc. On the Japan Email list other hand, it should be that ACPI is capable of detecting shutdown button presses as an event, making the operating system aware of it, and without running the risk as in APM, in addition to assigning IRQs for the devices so that designers can Exploit the savings features as you. ACPI is a standard by Intel, Microsoft and Toshiba initially. They the first implementation in , although after that some new revisions would come to support -bit, multiprocessors (MP), and new interfaces such as SATA, PCIe, USB x, etc.
ACPI Power States
ACPI also accepts various modes or states like APM, but they are different and more numerous in this case. For example, we have the: G-States or Global States and S-States or Sleep States: they are global states as. Gx and Sx, and they are: G or Working (S) : The computer is running and the CPU is executing instructions. G or Sleeping (Six) : is a modern standby state, an idle state where Australia Phone Number List part of the SoC is sleeping. It works on both ARM and x Six means that there may be intermediate states by the manufacturer. S (Power on Suspend or POS) : The processor cache is idle, and the CPU has executing instructions. But the power supply to the CPU and RAM is . Some devices may be off. The CPU is off, and the contents of the cache are to RAM. S or Suspend : The RAM maintains power so as not to lose the data it contains, but the system will be. S or Hibernation : It is a special sleep state, since instead of keeping the RAM, it returns its contents to secondary memory so that it is not lost and the system is shut down.
