PowerMac G4 FW800 not recognize more than 256MB RAM

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PowerMac G4 FW800 not recognize more than 256MB RAM

I have older PowerMac G4 FW800 1,25 DP and i have issue with ram. When i putting 256 stick into first slot (near cpu) everything is ok, i can install and run os x. But when i am putting other else size i cannot run or install os x. But i can boot Apple Diagnostic DVD and make some tests, everything passed with any size and amount ram. I tryed 256 sticks, 512 sticks and 1G sticks. Tests in AHT are good. But what is very funny, i tryed install ubuntu 10.04 for powerpc and everything runnig perfect with 2 1GB memory sticks in first two slots. Where is problem? Please help.

P.S. Sry for bad english

PowerMac, Mac OS X (10.4.11)

Posted on Jan 7, 2013 3:11 PM

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Answer 1

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Eustace Mendis

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25,416 points

Jan 7, 2013 5:00 PM in response to Luski1

How old is your PRAM battery? The FW800 G4 I owned worked best when the battery was new.

But before you go there (i.e. replacing the battery), try resetting the PRAM. With all the RAM installed, boot and immediately hold down the command + option + p + r (all four at the same time) keys. Keep holding the keys down for at least 2, better three sets of chimes. Release the keys after the third time it chimes.

Now check what RAM is recognized.

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Answer 2

Luski1 Author

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Jan 8, 2013 9:09 AM in response to Eustace Mendis

Hi Eustace

thank for your advice, i bought today a new battery but before replacing i reset PRAM 3 times. But no success. When i start booting from OS X Tiger CD, boot start and then freeze. In machine is installed not original RADEON 9000 but 9600 PRO. Maybe this is problem, i dont know. Ubuntu still functioning without problems, but i can not install os x when more sticks and bigger than 256 are inside. I dont know what next i must do. Please help.

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Answer 3

Jan 8, 2013 9:18 AM in response to Luski1

I would start by testing the RAM slots. Put the 256 in each of the slots in turn and see if the G4 boots. If all the slots are ok with that module, try a different module, by itself. And test the slots again.

You may be the victim of incompatible RAM modules, viz. modules that work alone but do not when paired with a different type. Only way to test that is by trial and error.

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Answer 4

Luski1 Author

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Jan 8, 2013 1:02 PM in response to Eustace Mendis

Hi,

ok, that was lot of testing. What i done: one stick 256 in random position is ok, os x boot and functioning normally. But when i put second 256 stick into memory slot (2x256) system can not boot and freeze (sometimes on wheel, sometimes gray power off window). When i putting into any memory slots bigger stick than 256, os x not boot. Curiosity is none of that memory issue appear in ubuntu. Hmm, it will be a strange problem. Actually tests in AHT passed, all sticks are recognized (any size, any position). I have lot of memory sticks at home (256, 512, 1G from random manufacturer) Whats next?

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Answer 5

Jan 8, 2013 1:29 PM in response to Luski1

Do you have two hard drives in the G4? I have no ubuntu experience, so I must ask do 10.4 and ubuntu reside on the same drive?

If only one drive, what is the jumper setting, main or cable select? Same question, if two drives what are the jumper settings?

One more question, what cards are in the pci slots?

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Answer 6

Luski1 Author

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Jan 8, 2013 1:36 PM in response to Eustace Mendis

Yes, i hawe two hard drives, one for ubuntu (clean install) and second for os x (clean install with 256 MB RAM). When i testing, hard drives not connected together. One is on ATA66 channel second on ATA 100 channel and when i am testing os x, UBUNTU hard drive is not powered and connected.

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Answer 7

Jan 8, 2013 1:41 PM in response to Luski1

Suggest you try switching the OS 10.4 drive to the other bus? And set the jumper on that drive to Cable Select.

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Answer 8

Luski1 Author

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Jan 8, 2013 1:52 PM in response to Eustace Mendis

Hi,

that all i tryed before, but still the same. Wherever the hard drive is, not booting with more RAM. It is something special on firmware or somewhere to reset? I can not imagine differencies between communication with ram on os x and ubuntu. I am lost now 😟

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Answer 9

Jan 8, 2013 1:58 PM in response to Luski1

Yes, I agree this is most frustrating. To my knowledge there was no firmware update to the G4 FW800. (I owned one some years ago.)

http://support.apple.com/kb/HT1395

If I have any other ideas, I will certainly get back to you. But in the meantime, like you I am at a dead end.

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Answer 10

Jan 8, 2013 2:03 PM in response to Luski1

Another thought / question:

What is your graphics card - the original AGP or an add on pci?

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Answer 11

Luski1 Author

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Jan 8, 2013 2:07 PM in response to Eustace Mendis

AGP Radeon 9600 pro, nomal recognized in 256MB installation of Tiger. But i think it is not original Apple. Thank you for your help, when you will have some other ideas i will be appreciated. 🙂

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Answer 12

japamac

Level 7

24,400 points

Jan 9, 2013 5:34 AM in response to Luski1

I don't know what DIMMs you are using, but if you mix PC2100 and PC2700 DIMMs, the PC2700 will allow the machine to start, but the PC2100 DIMMs will be invisible to the Mac OS.

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