If you’re experiencing severe and/or persistent problems with your Mac (it won’t turn on, for example) and the usual tricks don’t work, there are some less well-known fixes you can try, such as resetting the SMC (System Management Controller).

The SMC stores settings related to power and temperature management, among other things, and if it starts to misbehave this can result in problems with both noise and performance. It’s therefore worth resetting it if more obvious solutions (such as force-quitting apps, restarting the Mac) don’t help.

The way you resort a Mac’s SMC depends on the kind of Mac you’re dealing with, and whether or not it has a removable battery.

Desktop Macs

Follow these steps to reset the SMC on an iMac, iMac Pro or Mac mini.

• Shut down the computer.
• Unplug the power cord.
• Wait 15 seconds.
• Reattach the power cord.
• Wait five seconds, then press the power button to turn on the computer.

Recent MacBooks (with non-removable batteries)

Follow these steps to reset the SMC on a MacBook if its battery is non-removable. That includes all MacBook Airs, and MacBook and MacBook Pros from 2009 or later. More details here.

• Shut down the computer.
• Unplug the power cord.
• On the built-in keyboard, press and hold down the (left side) Shift, Ctrl and Option (Alt) keys, and the power button at the same time. Hold them all down for 10 seconds.
• Release all the keys and the power button at the same time.
• Press the power button to turn on the computer.

Note: The LED on your MagSafe power adapter may change states or temporarily turn off when you reset the SMC.

Older MacBooks (with removable batteries)

Follow these steps to reset the SMC on a MacBook with a removable battery. If your laptop is from earlier than mid-2009, that probably applies to you, but check here for details.

• Shut down the computer.
• Unplug the power cord.
• Remove the battery.
• Press and hold the power button for five seconds, then release it.
• Put the battery back in.
• Reattach the power cord.
• Turn the MacBook back on.