System Management Controller

The System Management Controller (SMC) is a subsystem of Intel processor-based Macintosh computers. It is similar in function to the older SMU or PMU of non-Intel Macintosh computers.

Overview

The SMC has roles in controlling thermal and power management, battery charging, video mode switching, sleep and wake, hibernation, and LED indicators. It also enables enforcement of the Mac OS X End User License, allowing it to identify when it is running on non-Apple hardware.

Apple releases occasional model-specific updates to SMC firmware which correct bugs and defects in the system.

Corrupted SMC firmware, whatever the cause, is not entirely uncommon and may lead to operational problems. Resetting the SMC may resolve certain issues with:

Fans

• Cooling fans running at high speed.

Lights

• Keyboard Backlight Issues.
• Incorrect behavior with the Status Indicator Lights or Battery Indicator Lights.
• Backlight displays not responding to ambient light changes.

Power

• Non-responsive power button
• Unexpected sleep or shutdown
• Battery not charging properly
• MagSafe LED displays incorrect activity

System Performance

• Computer running slowly despite low CPU load
• Long "Bounce" times for application icons in the dock.

External displays and Ambient Light Sensing

• Unexpectedly switching into or out of target display mode for external displays.

Port Illumination

• I/O Ports on some late model 2013 Mac Pro's don't illuminate when the computer is moved.

Resetting the SMC is usually accomplished by removing all power from the system for a period of time (by unplugging the mains connector or removing the battery) or by operating the power button in a special way. Apple provides model-specific instructions for SMC reset.

See also

• Power management integrated circuit (PMIC)
• Power Management Unit (PMU)
• System Management Unit (SMU)

External links

• EFI and SMC firmware updates for Intel-based Macs