Zapping the PRAM-NVRAM in OSX

What’s in the PRAM?

PRAM in OSX stores user specific system and device settings. The exact settings stored in your computer’s PRAM varies depending on the type of computer as well as the types of devices and drives connected to the computer.

Some information stored in the PRAM includes:

  • Display and video settings such as refresh rate, screen resolution, number of colors
  • Startup volume choice
  • Speaker volume
  • Recent kernel panic information
  • Status of AppleTalk
  • Serial Port Configuration and Port definition
  • Alarm clock setting
  • 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
  • DVD region encoding

Note: Mac OS X stores your preselected DVD region choice in PRAM. Resetting PRAM does not allow you to change the DVD region.

Unfortunately, Mac OS X does not store network settings in the PRAM anymore so if you’re trying to alleviate a network issue zapping the PRAM will not be of much help.

You may need to verify your time zone, startup volume, and volume settings using System Preferences after you’ve zapped the PRAM.

Resetting PRAM and NVRAM

  1. Shut down the computer.
  2. Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
  3. Turn on the computer.
  4. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
  5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
  6. Release the keys.

Your computer’s PRAM and the NVRAM will be reset to the default values. On some models you may also notice the clock settings reset to a default date and time. This is normal.

For more information on resetting your PRAM visit

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