Power (SMC / PMU) Resetting on Apple hardware

For more information of power reset please consult http://support.apple.com/kb/ht3964

Resetting the SMC for MacBooks

Note: Portable computers that have a battery you should not remove on your own include MacBook Pro (Early 2009) and later, all models of MacBook Air, and MacBook (Late 2009).

1. Shut down the computer.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if it's not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer. Note: The LED on the MagSafe power adapter does not change states or temporarily turn-off when you reset the SMC.

Resetting the SMC for Mac Pro, Intel-based iMac, Intel-based Mac mini, or Intel-based Xserve

1. Shut down the computer.
2. Unplug the computer's power cord.
3. Wait fifteen seconds.
4. Attach the computer's power cord.
5. Wait five seconds, then press the power button to turn on the computer.