If your Mac is acting up and you can’t figure out why, you might try resetting the NVRAM or the SMC. I’ll show you how.
Modern Macs have a bit of NVRAM--the NV stands for “non-volatile”--and it stores information like your selected startup disk, speaker volume, screen resolution, and time zone.
If you’re having startup problems, you might try resetting it. Here’s what you do.
First, shut down your Mac.
Then, turn it on and immediately press and HOLD DOWN, these keys: Option, Command, P, and R.
You can let go after you hear the startup sound, and you’re good to go.
Why P and R? Well, Macs used to have “parameter RAM” that was simliar to the NVRAM in modern macs. So they just kept the shortcut.
NVRAM is not usually the cause of your problems. More often its the SMC, or System Management Controller
That’s the part of your Mac that deals with power management, charging, fan control, keyboard lights...stuff like that.
Resetting the SMC is done a little differently for different kinds of Macs. But you always start by shutting down first.
Then, if you have a desktop Mac or iMac, just unplug the power cord. Wait 15 or 20 seconds, plug it in, wait another 5 or 10 seconds, and power on the system again. On a desktop system, this power cycling is all you have to do to reset the SMC.
If you have a mac laptop, make sure it’s unplugged and powered down. Then hold down Shift, Control, and Option on the LEFT side of the keyboard. While holding those down, press and HOLD DOWN the power button. Hold down all these buttons together for 10 seconds, then release. The you can plug in your laptop and boot it up like normal.
If you have an old mac laptop that has a removable battery, just shut down, unplug it, and remove the battery. Hold the power button down for 5 seconds, and release. Then put the battery back in, plug the laptop in, and power it on.
Resetting the SMC or NVRAM is not a guaranteed fix. But it doesn’t take long and it doesn’t delete any data from your hard drive, so it’s usually worth a shot.