Blog by an Apple Certified Tech

What is PRAM or NVRAM

Any person using Mac OS X machine might have heard of the term PRAM or NVRAM. These both are similar things, the only difference is that in Power PC based Mac machines it was termed as PRAM which stands for Parameter Random Access Memory and NVRAM is Non Volatile Random Access Memory which is in iMacs.

What is the purpose of PRAM or NVRAM?
The main purpose of PRAM or NVRAM is to save some settings related to hardware or software related to the system. In iMacs these are Screen resolution, display settings, video and screen refresh rate, recent kernel panic information (if there is any recent one), DVD region settings.

How PRAM or NVRAM works?
In an intel based MacBooks NVRAM takes power from the backup battery, however in other models it takes little (trickle) power from the main source to store data.

The information saved in PRAM or NVRAM are:

  • 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

So if there is any issue related to the above listed items, you can go for PRAM or NVRAM reset, hopefully it should fix the issue. Other issues where resetting PRAM or NVRAM would work are: Mac freezing or is not booting up after the grey screen.