Resetting PRAM and NVRAM

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.

After resetting NVRAM or PRAM you may need to reconfigure your settings for speaker volume, screen resolution, startup disk selection, time zone information. If issues persist, your Mac’s logic board battery (not a portable Mac’s rechargeable battery) may need to be replaced. The logic board battery helps retain NVRAM/PRAM settings when your computer is shut down. You can take your Mac to a Mac Genius or Apple Authorized Service Provider to replace the battery on the logic board.

Contents of PRAM

  • 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

Your Mac stores certain settings in a special memory area even if it is turned off (unless there is a battery issue as described below).  On Intel-based Macs, this is stored in memory known as NVRAM; on PowerPC-based Macs, this is stored in memory known as PRAM. Information stored in NVRAM or PRAM may include:

  • Speaker volume
  • Screen resolution
  • Startup disk selection

You may need to reset the NVRAM or PRAM if you experience issues related to these functions.
For example, if your Mac starts up from a startup disk other than the one you’ve specified in Startup Disk preferences, or if a “question mark” icon appears briefly when your Mac starts up, resetting NVRAM or PRAM may help.

Case: If you have a problem with internal sound cannot switch to headphone/earphone. Maybe you can try this method.
Source: http://support.apple.com/kb/HT1379

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Posted in: Mac

This entry was posted on Tuesday, February 28th, 2012 at 2:59 am and is filed under Mac. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.