Reset PRAM and NVRAM on a Mac

This page explains how to reset the PRAM (Parameter Random Access Memory) and NVRAM (Non-Volatile RAM) on Apple Macintosh computers.

Note: If your problem is that the Mac loses PRAM settings when it is turned off, this probably means that the battery is dead and needs replacing. See Macintosh Batteries & Parts.

1. Shut down the computer.
2. Locate the following keyboard keys and get ready to press them all down at once: Command, Option, P, and R.
3. Turn on the computer.
4. Quickly press and hold the Command-Option-P-R keys — ideally before the gray screen appears.
5. Keep holding the keys down until you hear the startup sound at least twice (some users recommend 3 or 4 times).
6. Release the keys.

After resetting the PRAM you should check the settings listed below using System Preferences.

What is PRAM anyway?

PRAM is an area of memory that stores various system-related settings. PRAM is is a sub-section of NVRAM and is retained when the computer is shut down. Exactly which settings are stored in PRAM depends on the type of Mac and the types of connected devices. Some or all of the following settings may be included:

• AppleTalk status
• Serial Port Configuration and Port definition
• Clock settings
• Application font
• Serial printer location
• Autokey rate
• Autokey delay
• Speaker volume
• Attention (beep) sound
• Double-click time
• Caret blink time (insertion point rate)
• Mouse scaling (mouse speed)
• Startup disk
• Menu blink count
• Monitor depth
• 32-bit addressing
• Virtual memory
• RAM disk
• Disk cache