System management controller

The system management controller (SMC) is responsible for managing the power-related features of Intel-based Macintosh computers. On models that have an Apple T1 or T2 security chip, the SMC is managed by the chip to maintain startup security and prevent unauthorized access.

Managed features

 * The power button.
 * Battery and charging.
 * Fans and thermal-management features.
 * Power to the USB ports.
 * Sensors, such as the sudden motion sensor, the ambient light sensor, and keyboard backlighting sensor.
 * Sleep behavior when opening and closing the lid of a notebook computer
 * Status indicator lights, such as sleep status and battery charging status.

Resetting the SMC
If there are power-related issues with a noteook Mac managed by a SMC, the controller can be reset by shutting down, holding down      for at least 7 seconds, and then also hold down the power button for at least 10 seconds. The SMC can be reset on a desktop Mac by shutting down, unplugging it from power for at least 15 seconds and then plugging it back in for at least 5 seconds before turning it back on. This process does not affect data stored in NVRAM or PRAM.

Newer Macs based on the Apple M1 processor do not contain a SMC that can be reset in this manner.