NVRAM (nonvolatile random-access memory) is a small volume of memory used by Mac to store certain settings and to be able to access them quickly in generic operations. In NVRAM are stored information such as: the volume, display resolutionboot disk (startup disk), Time zone (time zone) and recent information about kernel. There may be other settings stored in NVRAM, depending on the model MacFor example, on models MacBook Pro 2017 and MacBook Pro 2016, in NVRAM settings such as “storedAutomatic start-up of the system after opening the lid (lid)”- you can find more in this tutorial.
If you encounter problems with these settings, NVRAM reset could be the saving solution. Writing some erroneous information on NVRAM or corrupting this memory space from various causes, can lead to settings errors previously announced. All this can be corrected by resetting NVRAM.
How to reset NVRAM (NonVolatile Random-Access Memory) on Mac / MacBook
1. Close Mac / MacBook. Shut Down...
2. Switch Mac then immediately press si keep the presses keys Option, Command, P si R.
3. While Mac gives signs to restart after approx 20 seconds release these four keys. On Macthe sounds that sound when the system is started macOS, you can release the four keys immediately after playing the sound. On iMac Pro you can release the keys after the logo Apple appears and disappears a second time.
After rebooting you may need to go to "Preferences" to restore the sound, boot disk, screen resolution and other settings that were stored by NVRAM.How to reset NVRAM (NonVolatile Random-Access Memory) on Mac - Solving Many Problems