When to reset your NVRAM (formerly PRAM)
No doubt, if you've called Apple for troubleshooting in the past, it is likely that someone has told you to reset your NVRAM (formerly known as PRAM). In our experience, this procedure is one of the most misused, and misunderstood steps in our troubleshooting arsenal. So what exactly is the NVRAM, and when should we reset it?
First, lets understand what the NVRAM is; it stands for Non-Volatile RAM, which is the Intel-based mac version of what used to be known as Parameter RAM (PRAM) on older Motorola-based Macs. The NVRAM and PRAM hold settings for your computer that needs to be held in storage independent of your operating system, and which are stored even when the computer is shut down. When your computer starts up, the volume the speakers are set to, your startup disk, and screen brightness are all determined by the values in your NVRAM. If you are having an issue with the screen brightness, computer volume or your startup disk not being found, resetting the NVRAM is a good troubleshooting step to try. Any other issues will not be resolved with an NVRAM reset, though performing one will not cause any ill effects.
How to do it:
1. Shut down or restart your computer
2. Turn the computer on, and immediately hold down all of the following keys:
3. Wait until you hear at least 2 chime noises from your computer
4. You're done! Hopefully your issue has been resolved.
5. If you hear only one chime, you didn't get to the keys fast enough, you'll need to start again