Parameter RAM (PRAM) is a small area of non-volatile RAM (NVRAM).The PRAM stores specific system and device settings in a location that Mac OS X can access quickly. Exactly which settings are stored in the computer’s PRAM varies depending on the type of computer as well as the types of devices and drives connected to the computer.

apple os x welcome screen logo

apple os x welcome screen logo

Some information stored in PRAM includes:

  • Display and video settings such as refresh rate, screen resolution & number of colors
  • Startup volume choice
  • Speaker volume
  • Recent kernel panic information, if any
  • DVD region setting

FYI: Mac OS X stores the DVD region you chose in PRAM for easy access. Resetting PRAM however, does not allow you to change your DVD region.

Unlike prior versions of the Mac OS, Mac OS X does not store network settings in PRAM. If you experience a network issue, resetting PRAM will not help.

If PRAM is reset, you will want to verify the time zone you selected, your computer’s startup volume, and any volume settings. You can do this in the System Preferences.

Certain firmware updates may reset PRAM as a normal part of their installation process.

To Reset the PRAM:

  1. Turn off/Shut down your Mac.
  2. Find the Command, Option, P, & R keys (You will need to press these keys simultaneously in a later step!).
  3. Turn on/Boot up your Mac.
  4. Before the gray screen appears, press and hold the Command, Option, P, & R keys until you hear the Mac start-up sound for a second time.
  5. Release the four keys to allow your computer to start up normally.
  6. If this process does not work, disconnect any devices (except for the Monitor, Keyboard and Mouse), which are connected to your computer (I.E. Printer, Hub, iPod, or etc.), and repeat the first three steps again.

Some Information in this article was found here and here!