How to reset the PRAM on your Mac

TerminalIconXThe Parameter RAM, or PRAM, on your Mac is a small amount of non-volatile memory (ie, persistent memory that is not cleared when the power is off) that is used by the system to hold hardware configuration settings such as the audio volume at startup, the default boot disk, and various boot arguments to pass to the default operating system.

Sometimes specific problems your Mac may encounter are a result of corruption in the PRAM, where variables are not stored properly.

In these cases, the system may take a long time to boot as it searches for an appropriate boot volume instead of having a default one to use, or may always boot to Safe Mode or similar mode.

How to Reset

To reset the PRAM on your system, just follow these steps:

  1. Restart the computer
  2. Immediately hold down the Option-Command-P-R keys after hearing the boot chimes
  3. Hold the keys until the system resets and sounds the boot chimes again
  4. Release the keys when you hear the boot chimes sound, and allow the system to boot normally

If you continue to hold the keys down in step 3, then if you have a wired keyboard (such as a USB one, or that in a laptop), then the system will continue to receive the instruction to reset the PRAM, and will cycle through resets and restarts until you release the keys.

After Resetting

With the PRAM reset, your system will now populate it with default settings, but sometimes these may not be desired ones. When the OS loads, many such as system audio volume will be reset to stored values in the system preferences; however, to be sure, go to the system preferences and toggle the relevant settings. These include the following:

  1. The appropriate boot drive in the Startup Disk system preferences
  2. The volume of the system
  3. Location services being enabled or disabled (in the Security & Privacy system preferences)
  4. Display resolution and brightness
  5. iCloud settings
  6. Mouse cursor speeds

8 thoughts on “How to reset the PRAM on your Mac

    1. Douglas Thom

      Not true… When I worked in Tech Support at Apple, this was a common mis-conception, and many of my fellow support people repeated this notion. Only one cycles of the boot chime with Command-Option-P-R was ever required. This was true from the beginning.. Amazing how the propagated over the years.

  1. MissMac (@missmacmac99)

    for fix this audio issue on os x yosemite you can try

  2. Sietse

    So am I totally ****** when after following these steps still getting a apple logo and progress bar not getting any fuller than 40 to 50% and the mac shutting down?

  3. Claude Meunier

    To Sietse…I own a late 2009 model Imac 27 and I have the exact same thing as you since jan 26 ! I ran the hardware troubleshooting tool and found 3 codes all related to HDD : 4MOT/4/40000003:HDD-1242 , 4MOT/4/40000003:HDD-1235, 4MOT/4/40000003:HDD-1238. I opened my machine and thoroughly cleaned inside, especially at both fans (because MOT in my three codes refer to fan speed) and re-ran the short test and this time I did not find a single error! Re-started and same as beginning! Pretty frustrating. Thinking of replacing my Seagate 1TB freshly replaced by Apple last year by a 1TB Samsung SSD

  4. W

    I’m not sure if this is good advice — but after trying all of this stuff nothing worked for me. Then after scanning some processes I saw that the airportd was acting erratically with CPU fluctuating all over the place. I executed
    sudo launchctl unload -w /System/Library/LaunchDaemons/
    and things /seem/ to be fine now. Not sure of any potential side affects but at least I can use my wifi now.

  5. darapuce


    I found a temporary solution. Attached the HDD to external usb and start the computer. Press ALT/Option choose the attached hard disk. It works for me to save my files.


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