System Management Controller

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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.[1]


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.[2]

Apple releases occasional model-specific updates to SMC firmware which correct bugs and defects in the system.[3]

Corrupted SMC firmware, whatever the cause, is not entirely uncommon[vague] and may lead to operational problems. Resetting the SMC may resolve certain issues with:[4]


  • Cooling fans running at high speed.


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


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

System Performance[edit]

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

External displays and Ambient Light Sensing[edit]

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

Port Illumination[edit]

  • 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.[5]

See also[edit]


  1. ^ Apple general documentation on SMC Updates
  2. ^ "Interview with Andy Hall, Product Manager for Oracle VM VirtualBox". 
  3. ^ Search of SMC update information in Apple's knowledge base
  4. ^ Intel-based Macs: Resetting the System Management Controller (SMC)
  5. ^ Intel-based Macs: Resetting the System Management Controller (SMC)

External links[edit]