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 of non-Intel Macintosh computers.[1]


The SMC has roles in controlling thermal and power consumption, 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 and may lead to operational problems. Resetting the SMC may resolve certain issues, such as:

  • Cooling fans running at constant high speed
  • Computer running slowly despite low CPU load
  • Failure to recognize keyboard or trackpad
  • Failure to recognize add-on hardware or peripherals
  • Failure to recognize battery
  • Failure to wake from sleep, or unexpected sleep
  • Sudden unexpected power loss
  • Non-responsive power button
  • Poor battery performance
  • Non-operational LED indicators
  • Bluetooth Failure

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.[4]

See also[edit]

External links[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)