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An embedded controller (EC) is a computer microcontroller that handles system tasks. It is typically used on mobile computer platforms (such as laptops).
An embedded controller can have the following tasks:
As a core system component, the embedded controller is always on when power is supplied to the mainboard. To communicate with the main operating system, several forms of communication can be used, including ACPI, SMBus, or OEM-offered power management drivers.
The embedded controller has its own RAM, independent of that used by the main computer system, and often its own flash ROM on which the controller's software is stored. Many BIOS updates also include upgrades for the embedded controller firmware.
An embedded controller is sometimes known as a "Keyboard Controller BIOS", which comes from the fact that the embedded controller evolved from the keyboard controller and often continues as a keyboard controller. An ACPI embedded controller communicates with the CPU via the same I/O ports that keyboard controllers used in the past.
Although the embedded controller is "deep" in the system, it performs important functions for users such as fan control and thermal management. Laptops often produce large amounts of heat that must be discarded. This is typically done by activating a fan to blow air over the hot components; the fan is driven at variable speed by the EC. Such control schemes can be uncomfortable from an ergonomic point of view, as the change in fan speed is noticeable to the user.
Some embedded controllers are designed to run the fans at a relativey constant speed over a wider temperature range and increases fan speed only when the system is overheating. This allows the fan to operate more quietly.
