reset-all and zap PRam

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Level 4

2,312 points

reset-all and zap PRam

What is the difference between zapping PRam and giving the following commands in open firmware?

reset-nvram
set-defaults
reset-all

MBP 15, MBP C2D 17; iMacG5, TiBook, G4 MP500; G3 beige333, iMacs 333, 180C, more, Mac OS X (10.4.8)

Posted on Feb 5, 2007 11:22 PM

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Answer 1

Kappy

Level 10

362,007 points

Feb 5, 2007 11:55 PM in response to Judy

One is done at startup using the COMMAND-OPTION-P-R keys and the other is done through Open Firmware.

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Answer 2

baltwo

Level 9

62,386 points

Feb 5, 2007 11:57 PM in response to Judy

IIRC, the Open Firmware commands replicate the PRAM zap, but do more things. See http://docs.info.apple.com/article.html?artnum=60285 for details—they're applicable to nonserver machines.

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Answer 3

Judy Author

Level 4

2,312 points

Feb 6, 2007 12:14 AM in response to Kappy

Too little info.

Once the commands are invoked, is the same result accomplished? Or is one method better than another?

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Answer 4

Judy Author

Level 4

2,312 points

Feb 6, 2007 12:15 AM in response to baltwo

Too much info, but interesting.

Once the commands are invoked, is the same result accomplished? Or is one method better than another?

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Answer 5

Kappy

Level 10

362,007 points

Feb 6, 2007 12:23 AM in response to Judy

Yes, the same result is accomplished.

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Answer 6

baltwo

Level 9

62,386 points

Feb 6, 2007 12:30 AM in response to Judy

Not enough info—too much info? WOW. You asked, I answered that they both zap the PRAM. I'm sorry if you think there's too much informatiion to digest WRT to the Open Firmware article. I guess you'll not find out.

Cheers

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Answer 7

Judy Author

Level 4

2,312 points

Feb 6, 2007 12:51 AM in response to baltwo

Why is it advised to hold Command-option-PR for 3 or more chimes worth?
Do the open firmware commands accomplish the resetting just by giving the commands one time?

WRT the article, what will I not find out?

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Answer 8

Kappy

Level 10

362,007 points

Feb 6, 2007 7:15 AM in response to Judy

As far as I am aware Apple's instructions state you only hold the keys until you hear the chime for the second time (the first being the startup chime.) There's no difference between this and using OF unless you don't restart the computer, but then there would be little point in that.

As for the article reference you can read it and learn more or not read it. It's up to you. It has nothing new with respect to resetting the PRAM.

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Answer 9

Judy Author

Level 4

2,312 points

Feb 6, 2007 11:21 PM in response to Kappy

This has been interesting.
I had the problem of my G4 Mac going to sleep and not being able to wake it up after I installed 10.4.8. I had to reboot.

I deleted com.apple.PowerManagement.plist. That did not help.
I zapped the PRam. That did not help either.

Only after I went into open firmware and ran those 3 commands was my Mac working correctly again.

Yet you have said the zapping and the commands accomplish the same thing. I think there must be a difference somewhere.

BTW, I did read the article but did not digest all of the details yet.

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Answer 10

Judy Author

Level 4

2,312 points

Feb 13, 2007 9:12 PM in response to Kappy

Someone said that zapping the PRAM does not reset nvram on Power Mac systems.
But resetting nvram is not needed on Intel Macs.

Is this the distinction?
So I only need to remember to zap PRam for an Intel Mac?

Perhaps this is why zapping did not work on my G4 PowerMac.

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Answer 11

Kappy

Level 10

362,007 points

Feb 13, 2007 9:17 PM in response to Judy

I'm certainly not aware of that being the case for PowerMacs. Zapping PRAM has been long a recommended procedure by Apple for clearing out data corruption in the permanent RAM. I have read claims that allowing three consecutive chimes would clear out parts of PRAM that one cycle would not. But I've not seen anything from Apple to that effect (not that there may not be.)

A guaranteed way to completely clear the permanent RAM area is to simply remove all power to the computer or remove the PRAM battery if the computer has one.

Zapping PRAM is not a cure all. It only does specific things. It removes the data that the OS stores in the permanent RAM.

This document: http://docs.info.apple.com/article.html?artnum=2238 details what is stored in PRAM on Macs using OS 9.

This document: http://docs.info.apple.com/article.html?artnum=86194 details what's stored on Macs using OS X.

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