How to reset the MAC hardware

Reset Mac Hardware:-



NVRAM corruption is fairly uncommon, but if your Mac seems to take forever to figure out which disk to boot from, if it starts up with the wrong screen resolution, or if you have weird audio problems (like there’s no sound whatsoever, or the menu bar’s volume control is grayed out), it doesn’t hurt to reset the NVRAM—it’s quick and harmless.

To reset your NVRAM, you use exactly the same procedure you once used to reset PRAM.

-- Shut down your Mac.

-- Press the power button, and as soon as you hear the startup chime, hold down Command-Option-P-R.

-- Keep holding down those keys until you hear a second startup chime. Then let go and allow your Mac to continue starting normally.

-- Then check the Startup Disk, Display, and Date & Time panes of System Preferences to make sure they’re set the way you want them.