Intel-based Mac: resets the system management controller (SMC)

Summary

On Intel-based Mac, the system management controller (SMC) manages many low-layer functions. These functions include:

• Respond to power button pressing
• Responding to the opening and closing of the screen cover of a portable Mac Monitor
• Battery Management
• Thermal Energy Management
• SMS (Sudden Motion Sensor, emergency Motion Sensor)
• Environmental photometric sensing
• Keyboard Backlight
• State indicator light (SIL) Management
• Battery status indicator
• Select external (rather than internal) video sources for some iMac monitors

Sometimes, SMC may have problems, which may lead to abnormal system behavior. Such behavior is generally related to the symptoms described below. In some cases, resetting SMC may be the only way to solve the problem. However, you should try to reset SMC only after all other standard fault diagnoses are performed.

Affected Products

Portable laptop, desktop computer

Before resetting SMC

In the reset SMCBefore, Try the following steps in the following order. After completing the troubleshooting steps, perform a test to determine if the problem persists.

1. Press Command + Option + Escape to force exit any unresponsive application.
2. SelectApple ()Menu, and then selectSleepPut the Mac into sleep state. After the computer is sleep, wake it up.
3. SelectApple ()Menu, and then selectRestart, Restart the Mac.
4. SelectApple ()Menu, and then selectShutdownTo disable Mac.

If the Mac seems to be running normally but does not respond, press the power button for 10 seconds to force the computer off.Note: Any unstored data in any opened application will be lost.

For Mac portable computers, try:

1. Unplug the MagSafe power adapter from the Mac and wall power outlets and wait for several seconds.
2. Disable Mac. Remove the battery (if possible), re-insert the battery, and start the Mac.

If the problem persists after performing the preceding troubleshooting steps, you may need to reset the SMC.

After performing a regular fault diagnosis, if the following symptoms occur, it indicates that the SMC may need to be reset:

Fan
The computer fan quickly rotates and remains at a high speed.
Although the computer is not heavy and ventilated, the computer fan still rotates at high speed.

Indicator Light
The keyboard backlight is abnormal (on Mac computers with this function ).
Status Indicators (SIL) behave abnormally (on Mac computers with SIL ).
The battery indicator (if any) is abnormal (on a portable computer where the battery cannot be detached ).
The Display Backlight cannot properly respond to changes in ambient light (with this function on Mac ).

Power Supply
The computer cannot respond correctly when the power button is pressed.
Mac portable computers cannot respond correctly to the opening and closing of screen covers.
Abnormal sleep or shutdown on the computer.
The battery does not seem to charge properly.
The led of the MagSafe power adapter does not properly indicate the active status.

System Performance
Although the computer's CPU usage is not very high, the running speed is exceptionally slow.

Video
A computer that supports the target display mode cannot switch the Target Display Mode normally.
Allows an abnormal computer in the target display mode to enter or exit the target display mode.

Reset System management controller (SMC)

Reset SMC on Mac laptop with detachable battery

Note: Learn how to remove the battery of the MacBook and MacBook Pro.

1. Turn off your computer.
2. If the MagSafe power adapter is connected, unplug it from your computer.
3. Remove the battery.
4. Press and hold the power button for 5 seconds.
5. Release the power button.
6. Reconnect the battery and MagSafe power adapters.
7. Press the power button to open your computer.

Reset the SMC on a Mac portable computer equipped with a non-removable battery.

Note: Portable computers equipped with undetachable batteries include MacBook Pro (early 2009) and newer models, all models of MacBook Air and MacBook (late 2009 ).

1. Turn off your computer.
2. Connect the MagSafe power adapter to the power source and Mac (if not ).
3. On the Internal keyboard, press (left) Shift-Control-Option and power button at the same time.
4. Release all keys and power buttons at the same time.
5. Press the power button to open your computer.

Resets SMC on Mac Pro, Intel-based iMac, Intel-based Mac mini, or Intel-based Xserve.