NVRAM (nonvolatile random-access memory) represents a small volume of memory, used by the Mac to store certain settings and to be able to access them quickly in generic operations. NVRAM stores information such as: the volume, display resolution, the boot disk (startup-disk), Time zone (time zone) and recent information about kernel. There may be other settings stored in NVRAM, depending on the model of your Mac. For example, on MacBook Pro 2017 and MacBook Pro 2016 models, in NVRAM settings like "Automatic start of the system after opening the cover (lid)" - you can find more in This tutorial.
If you encounter problems related to these settings, reset NVRAM could be the saving solution. Writing some incorrect information on NVRAM or corrupting the memory space for various reasons, it can lead to setting errors previously stated. All of these can be corrected by resetting the NVRAM.
Cum resetam NVRAM (NonVolatile Random-Access Memory) pe Mac / MacBook
1. Shut down the Mac / MacBook. Shut Down…
2. Start Mac then immediately press and keep apasatele keys Option, Command, P and R.
3. While the Mac shows signs of restarting, after approx 20 seconds release these four keys. On Macs that have sound at macOS startup, you can release the four keys immediately after the sound plays. On the iMac Pro, you can release the keys after the Apple logo appears and disappears a second time.
After restarting, it may be necessary to go to "Preferences" to restore the sound settings, boot disk, screen resolution and other settings that were stored by NVRAM.
