OSXFAQ Mac OS X Tip-of-the-Day  

You Mac stores a small amount of essential configuration information in PRAM (Parameter Random Access Memory), which is retained when the machine is switched off and used when the machine is booted. Some parameters are:

Display and video settings such as refresh rate, screen resolution,
number of colors
Time zone setting
Startup volume choice
Speaker volume
Recent kernel panic information, if any
DVD region setting

Network setting are not stored in PRAM, as they were in OS 9.

If this information becomes corrupt it can cause startup and operational problems. To reset it, restart holding down the four-key combination:

Command-Option/Alt-P-R

Hold the keys until the computer restarts and you hear the startup sound for a second time.

Replace the PRAM battery if you find that these setting are continually being lost between reboots.

If you have a RAID setup zapping PRAM may cause your Mac to not startup. In this case try starting with the Option/Alt key held down to launch the Startup Manager, and choose an appropriate boot volume. Alternatively restart holding down the four-key combination:

Command-Option/Alt-Shift-Delete

Zapping PRAM also resets the NVRAM (Non-Volatile RAM) which contains the Open Firmware (OF). OF is code that initiates the boot sequence, for example, determining the startup volume. An alternative method of resetting PRAM and NVRAM is to restart holding down the four-key combination:

Command-Option/Alt-O-F

At the open firmware prompt '> 0' type:

reset-nvram (press return)
reset-all (press return)

and you Mac should reboot with a clean PRAM and NVRAM.

Here is some further information on Open firmware:

Quick reference:

Detailed information:

Enjoy !! :-)

Panther 10.3.8

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