Responds to the press of the power button, including deciding whether the press is for a power off, sleep, or an accidental misstep by your cat.
Detects and responds to the opening or closing of the lid of a portable Mac.
Manages a portable’s battery performance, including charging, calibration, and displaying remaining battery time.
Thermal management of your Mac’s interior. This is primarily accomplished by sensing temperature at various places inside your Mac, and then adjusting fan speed to create or reduce airflow.
Uses the SMS (Sudden Motion Sensor) to respond to the sudden motion of a Mac portable and acts to prevent damage to various devices.
Detects ambient lighting conditions and sets appropriate lighting levels for various devices.
Controls SILs (Status Indicator Lights) that are present on or in your Mac.
Selects external or internal video sources (primarily for iMacs with video input capabilities).
Starts hard drive spin downs, as well as power up sequences.
Controls sleep mode functions (waking and entering sleep).
Display backlight not responding to ambient light level changes.How to Reset Your Mac’s SMCThe method for resetting your Mac’s SMC depends on the type of Mac you have. All SMC reset instructions require shutting down your Mac first. If your Mac fails to shut down, try pressing and holding the power button until the Mac shuts down, which usually takes 10 seconds or so.
Press and hold the power button for at least 5 seconds.
Connect the MagSafe power adapter to your Mac and to a power outlet.
On the built-in keyboard (this will not work from an external keyboard), simultaneously press and hold the left shift, control, and option keys while you press the power button. Release all keys at the same time.Press the power button to start your Mac.
If you have a Mac Pro that isn’t responding to the normal SMC reset as described above, you can force a manual SMC reset by using the SMC reset button located on the Mac Pro’s motherboard.
Unplug the Mac’s power cord.
Open the Mac Pro’s side access panel.
Just below the Drive 4 sled and adjacent to the top PCI-e slot is a small button labeled SMC. Press and hold this button for 10 seconds.
Close the Mac Pro’s side door.
Start your Mac by pressing the power button.Now that you have reset the SMC on your Mac, it should be back to operating as you expect. If the SMC reset didn’t fix your problems, you can try combining it with a PRAM reset. Although the PRAM works differently than the SMC, it can, depending on your Mac model, store a few bits of information that the SMC uses.