How to Reset the PRAM in an iMac
Occasionally it may become necessary to reset certain aspects of your computer, such as the PRAM (parameter random access memory) to fix certain issues that may occur. Resetting the PRAM of a Macintosh computer is generally the solution to many issues such as a faulty monitor display, drives failing to mount, boot issues and other things that cannot be solved with a simple restart. Resetting the PRAM in an iMac is simple to do and shouldn't take more than a few minutes to complete.
Shut down your computer completely. If you cannot access the shut down menu, you can hold the power button down until the machine shuts down. If this does not work, you can unplug it from the wall, but this is not recommended unless there is no other way to shut it down.
Locate the "Command," "Option," "P" and "R" keys on your keyboard. The Command and Option keys are generally located directly to the left of your space bar. You will need to press these keys all at the same time, so be prepared to do so.
Turn on the iMac. Immediately press and hold down the "Command," "Option," "P" and "R" keys on your keyboard. This must be done before your computer displays the gray startup screen, otherwise it may not work.
Continue holding the keys down until the computer restarts itself again, and you hear the startup chime. You may then release the keys, and your computer will boot up to your login screen or desktop.
Tips & Warnings
- Many basic issues can be solved by resetting your PRAM, and it won't cause any adverse effects if it is successful. The PRAM simply resets certain features and options like speaker volume, autokey rate and other basic functions.
- This way of resetting PRAM works on all versions of Mac OS 9 and above.