Whenever your Mac has some problems related to settings stored in NVRAM or PRAM, resetting it can help.
NVRAM (nonvolatile random-access memory) is really a small amount of memory that your Mac uses to save certain settings and access them rapidly. PRAM (Parameter RAM) stores similar information, and the steps for resetting NVRAM and PRAM are the same.
Actually, settings that can be stored in NVRAM contain sound volume, display resolution, startup disk selection, time zone and recent kernel panic information. The settings stored in NVRAM depend on your Mac and the devices that you’re using with your Mac.
If you face some issues related to these settings or others, you should reset NVRAM and it can be helpful. For instance, if your Mac starts up from a disk other than the one selected in Startup Disk preferences or a question mark icon temporarily appears before your Mac starts up, you may need to reset NVRAM.
How to reset NVRAM
Shut down your Mac, then turn it on and press and hold these four keys together immediately: Option, Command, P and R. You can release the keys after around 20 seconds, during which time your Mac may appear to restart.
- On Mac computers that play a startup sound, you can release the keys after the second startup sound.
- On Mac computers that have the Apple T2 Security Chip, you should release the keys after the Apple logo appears and disappears for the second time.
Exactly, when your Mac finishes starting up, you may want to open System Preferences and set any settings that have been reset, like sound volume, display resolution, startup disk selection or time zone.