编辑 How to reset NVRAM and PRAM on a Mac

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Nonvolatile random-access memory (NVRAM) is a small amount of memory that your Mac uses to store certain settings and access them quickly. Older Macs store similar settings in Parameter RAM (PRAM). The steps for resetting NVRAM and PRAM are the same.

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NVRAM stores peripheral data such as volume, display resolution and brightness, startup-disk selection, and time settings. Resetting the NVRAM is a quick, easy, way to troubleshoot a misbehaving Mac—it doesn’t delete any data from your storage drive, and it doesn’t require any tools or repair experience. If you are experiencing problems related to your speakers, display, or other peripherals, you can try resetting your NVRAM on your own with the directions below.

=== Common NVRAM-Related Issues ===

* A blinking question mark icon appears briefly before your Mac starts up.
* Your Mac’s display freezes or becomes unresponsive (without showing the spinning wheel icon.
* Your Mac’s speakers intermittently stop playing sound, even though the volume is turned up.
* Your Mac has difficulty connecting to an external display.

== How to Reset NVRAM ==

# Shut down your Mac.
# Press and release the power button, then immediately press and hold the following keys: ***option***, ***command***, ***P***, and ***R***.
# Hold those four keys for about 20 seconds, or until your Mac boots twice (after the Apple logo appears twice).

If you are holding the correct key combination and the Mac is booting normally, it may not be registering your key presses. Try using a wired keyboard (or the built-in keyboard on a laptop Mac), and disconnecting any other USB and bluetooth connections.

== Apple Silicon Macs ==

Macs with Apple Silicon processors will not perform an NVRAM reset since the architecture of the logic board is much different. Settings previously stored in NVRAM are now likely a part of the processor itself. Simply shutting down or restarting your Mac is sufficient in this case.

== More Information ==

* After the NVRAM has been reset, you may want to go into System Preferences and restore any settings that have been reset (such as volume and display brightness levels).
* Some Macs have a small battery that exclusively powers the NVRAM. If your settings are reset every time you unplug your desktop Mac or when your laptop Mac battery dies, you may need to replace your NVRAM battery.
* If you are experiencing sleep, wake, charging, or other power-related symptoms, you may need to reset your [[How to reset the SMC on a Mac|System Management Controller|new_window=true]].

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