What does Command + Option + P + R actually do?

Question

Level 1

101 points

What does Command + Option + P + R actually do?

I was having my first ever startup issue with an Apple computer after 10 years of flawless performance ... now I'm scared 😟

I found the startup button combination mentioned in the troubleshooting guide, Command + Option + P + R and lo and behold it worked. Can anyone share with me what that does to help it start up? And possibly, more importantly, what problem is that showing or foreshadowing if I needed to use it?

The issue started last night I plugged in my shuffle to let it sync and charge, came back to my computer this morning and iTunes hung up (beachball), then iPod showed 2 icons in iTunes (one mine, one generic), then after a couple minutes of mroe beachball said iPod may be corrupt and I could not Force Quit anything.

Powered down, and when I powered up, I got a grey screen, no apple icon, no spinning line, no folder/question mark, nothing. I tried to start up from the restore CD ... and would only allow me to try and install. There was no hard disk that could be located at all to select or try to repair? I'm fearing for the life of this laptop, and it isn't that old. I'm curious what the button combination assisted with so I can be aware, or know if there is something I need to do now that it finally started back up and "appears" normal. Thanks for any more info, sorry for the long post, but thank you for reading.

Very nervous,
Mark

12 Powerbook G4, 1.33GHz, Mac OS X (10.3.x)

Posted on Nov 12, 2008 6:36 PM

Reply

Answer 1

Best reply

Kurt Lang

Level 9

57,692 points

Nov 12, 2008 7:08 PM in response to melange

Hello melange,

That key combination is know as "zapping the PRAM". The PRAM is a programmable chip that holds various bits of information about your computer's hardware along with other items. It's role is similar to a BIOS chip in a typical PC.

If the PRAM information gets mangled, your Mac can become anywhere between slightly and completely confused as to how your Mac is configured. If the info is corrupted enough, the Mac's firmware can't figure out how much RAM is installed, what type of video hardware, drives installed, etc.

Zapping the PRAM clears that data so the firmware can reexamine the Mac for installed hardware and put the correct information back in the PRAM.

More information on it here.

Reply

Answer 2

melange Author

Level 1

101 points

Nov 12, 2008 8:25 PM in response to Kurt Lang

Thanks Kurt for the explanation. Well, it worked once, and then I got the spinning beachball and couldn't get it to go away again. I now cannot get my computer to restart no matter what I try (I am writing from my wife's computer). It won't restart as before if I try the PRAM trick, I can't even boot from the restore disc, it hangs up and won't let me access disk utility ... I am unfortunately at a total and frustrating loss of what to do next. I cannot even access the hard drive when linking to my wife's with mine as a target firewire drive ... it just beachballs and can't read my drive. Short of taking it in I suppose. 😟

Do you (or anyone) happen to recommend a 3rd party authorized Apple repair service over taking it to the Genius Bar at an Apple shop?

Reply

Answer 3

Kurt Lang

Level 9

57,692 points

Nov 13, 2008 5:48 AM in response to melange

Try this.

First, unplug all peripherals except the keyboard and mouse. Then reset the Mac from Open Firmware, which is a more thorough wipe of the PRAM than zapping it.

Resetting the Mac from Open Firmware.

Restart the Mac and immediately hold down the Command Option+OF keys. This will boot you into open firmware. When it stops, you will be looking at a ">" prompt. At the prompt, type each of the next three lines, followed by pressing the Return key. Type each line exactly as show (without the (press Return) part), no capital letters or spaces.

reset-nvram (press Return)
set-defaults (press Return)
reset-all (press Return)

The Mac should restart after pressing Return on the third command.

Reply

Answer 4

melange Author

Level 1

101 points

Nov 13, 2008 1:35 PM in response to Kurt Lang

I will definitely try that tonight Kurt, thank you for another attempt so I can give the old college try. Can I ask, how do you determine if a hard drive is "dead" and needs to be replaced? Because all things I have encountered have me thinking that way, but I am not a computer expert by any means. Are there some specifics that would pinpoint that is the issue where replacing it would be the correct and only fix?

Thanks again if you have another moment.
Mark

Reply

Answer 5

Kurt Lang

Level 9

57,692 points

Nov 13, 2008 1:59 PM in response to melange

Can I ask, how do you determine if a hard drive is "dead" and needs to be replaced?

There are various ways. Sometimes you can feel the drive running when you grab the casing (don't touch the circuit board on the bottom). The ol' automotive shop trick works, too. Put a metal rod on the casing and put the other end next to your ear. You should be able to hear it running.

Spinning doesn't mean it's working though. The drive could be going around, but the actuator arms that move the read/write heads may have failed. Or something on the circuit board, such as a resistor, may have blown.

You could remove the drive and place it into an external drive case to see if it's working. Or connect it to an open EIDE cable and power connectors in another Mac. I'm assuming a G4 Powerbook is going to be EIDE, not SATA.

If you do want to try the hard drive in another Mac, make sure to turn the Mac off before disconnecting the drive. Also make sure the Mac you're connecting it to is off first. EIDE is not a hot connector like FireWire or USB. You could fry something trying to remove or connect the drive with the Mac still on.

Reply

Answer 6

melange Author

Level 1

101 points

Nov 14, 2008 11:04 AM in response to Kurt Lang

Well Kurt, the Open Firmware attempt was the only thing that got my Mac to startup. It was shaky, full of hangups, made a lot of extra noise, etc. But worked, so I was able to backup a few last minute things I needed.

I was then able to boot from the install disk, run disk utility, and repair hard drive. I ran it twice, once said it repaired part of it, the second took care of the rest. I was pretty excited. So I proceeded to try to restart.

It took a real long time, hung up at a few stages of the startup process, but started. As soon as I launched an application, i was able to use it for about 5 minutes, and then more and more beachballs. Finally, deja vu, I could not Force Quit anything. Had to manually power down, and try to restart and grey screen again ... not sure if that gives anymore indication of anything? But it seems the Open Firmware worked temporarily which helped me try a few things. But maybe to no prevail.

Your assistance has been great thus far.
I'm debating if it is time to try a new hard drive, but I don't know if that is the only issue going on, or if I would just invest in that only to be still stuck here.
Mark

Reply

Answer 7

Kurt Lang

Level 9

57,692 points

Nov 14, 2008 12:01 PM in response to melange

It sounds to me at this point that the hard drive is pretty much dead. At least you had it going long enough to back up the files you needed.

Reply

Answer 8

fugnug

Level 1

4 points

Nov 15, 2008 9:10 PM in response to melange

cmd + pr is not how you do it on a Powerbook.

I have a Titanium Powerbook myself and, the shortcut does not work.

Instead there is a tiny little button to zap the pram, hidden under the keyboard. I'm not sure why, but here is a pic that I just found on Google.

http://www.sonosphere.com/Doug/Archives/2003/06/PBG4_PMUResetButton.jpg

It's tiny, but when you press it you can tell it's a button. To lift the keyboard, pull the two triggers one between the Escape key and F1 and the other in between F11 and F12.

Message was edited by: fugnug

Message was edited by: fugnug

Reply

Answer 9

eww

Level 9

53,028 points

Nov 16, 2008 6:29 AM in response to fugnug

Hi, fugnug. What you're talking about is the Power Management Unit reset button. Resetting the PRAM is different from resetting the PMU, and is done on a Powerbook — as on any other Mac — by starting up while holding down the Command, Option, P and R keys.

Resetting PRAM and NVRAM
Resetting PMU

Reply