The System Management Controller (SMC) is a chip found in Intel Macs, responsible for maintaining various power, thermal, and firmware-related tasks.
The SMC is mostly equivalent to the Embedded Controller (EC) found in traditional x86-based PCs. It replaces the Power Management Unit (PMU) found in earlier Macs, and the System Management Unit (SMU) found in Macs with the PowerPC G5 processor. The SMC chip was merged to become part of the iBridge SoC in later Intel Macs, and finally, into the main SoC in Apple Silicon Macs.
Being a key way that Intel Macs differ from any other x86 PC, the SMC has the effect of being a de-facto method for the operating system to detect whether it is running on Apple hardware or not. Hackintosh projects FakeSMC and VirtualSMC overcome this by emulating a SMC device in software, translating the proprietary SMC functions to standard functions of the EC and other chips.
The SMC is responsible for:
- SMBIOS data: Acts as the source of truth on model/serial numbers for the hardware it has been installed in.
- Power: Responding to ACPI power state changes, managing turning on and off the computer, moving into or out of sleep and hibernation modes, waking up on scheduled alarms (such as PowerNap), and on Wake-on-LAN packets.
- Battery: Managing charging and discharging of the battery, in addition to monitoring battery charge and total capacity, regularly updating the OS with the current battery state.
- Thermals: Monitoring thermal sensors, adjusting processor power and fan speeds according to available thermal capacity.
- Real-time clock: Continual maintenance of the system clock, even when the operating system is shut down.
- Inputs/outputs: Management of the built-in keyboard, trackpad, and Touch Bar of MacBooks, including display, keyboard, and Touch Bar backlight level.
- LEDs: Management of power and battery capacity LEDs, on Macs with these features.
- Sensors: Monitoring of the ambient light sensor, and the hard drive sudden motion sensor on earlier MacBooks.