How to Reset PRAM and NVRAM in Mac OS X.
PRAM Stands for Parameter Random Access Memory and NVRAM Stands for Nonvolatile Random Access Memory. NVRAM is used in Intel based Macs. NVRAM is a type of random access memory which does not lose its information when power is turned off. PRAM is used in PowerPC based Macs. Parameter RAM is a small area of non-volatile RAM (NVRAM). PRAM stores certain 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.
Some information stored in PRAM / NVRAM includes:
* Time zone setting
* Startup volume choice
* Speaker volume
* Recent kernel panic information, if any
* DVD region setting
You may need to reset the NVRAM or PRAM if you experience issues related to the abovesaid 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 solve your problem.
Restore PRAM and NVRAM to Defaults :
- Shut down the computer.
- Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
- Turn on the computer.
- Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
- Hold the keys down until the computer restarts and you hear the startup sound for the second time.
- Release the keys.
- Your computer’s PRAM and the NVRAM are reset to the default values.