Avoid unnecessarily resetting the SMC or PMU for troubleshooting purposes
Summary
Special hardware in your Mac manages low-level tasks related to power management. On an Intel-based Mac, this is called the System Management Controller (SMC). On a PowerPC based Mac, this hardware is known as the Power Management Unit (PMU). You should not arbitrarily reset the SMC or PMU.
Products Affected
iBook, MacBook Pro, MacBook, PowerBook, Mac Pro, Power Mac, Mac mini, Mac OS
When should the SMC or PMU be reset?
You may need to reset your SMC or PMU only if you encounter issues that directly relate to one of these symptoms:
- Fans on high or system throttled when the system is not warm.
- Battery is not charging when it should be.
- LED on portable Mac's power adapter behaves incorrectly.
- Display/keyboard backlight adjustment does not work properly (for example, erratic behavior or no response) in response to ALS (Ambient Light Sensor).
- SIL (Status Indicator LED) behaving incorrectly on Macs that have a SIL.
- Incorrect response to power button press.
- Incorrect response to portable's lid open/close.
Note: On Intel-based Macs, resetting the SMC also will reset the contents of NVRAM.
Additional Information
For details about how to reset your Mac's SMC or PMU, click a relevant link below:
Intel-based Macs
PowerPC-based Macs
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