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Level 1

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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

Best reply

Eustace Mendis

Level 7

25,416 points

Posted on Jan 7, 2013 5:00 PM

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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21 replies

japamac

Level 7

24,400 points

Jan 9, 2013 1:37 PM in response to Luski1

i am using 2700 or 3200, but never mixed,

OS X is picky about RAM, so is the G4's firmware.

That MDD uses PC2700 DIMMs and the DIMMs must have 256 Mbit structure for other than 256 MB DIMMs. 256 MB DIMMs can have 128 or 256 Mbit structure.

High density DIMMs will usually not show in a G4. PC value RAM is usually high density.

Value and other mainstream PC RAM also doesn't have the necessary EEPROM coding for Macs, which can also cause problems in a G4.

Luski1 Author

Level 1

0 points

Jan 9, 2013 2:06 PM in response to japamac

Hi japamac,

thank you for your help. I know about that density, i am using really old RAM modules, some of them was removed from other powermac machines. My 256 sticks have chips on one side, 512 on both sides. But why then diagnostic disk normally tested and recognized all of the memory sticks and ubuntu normally functioning on that machine with 2 1GB memory sticks? Tomorrow i am going to my friend which have similar G4 and i will test my memory sticks on his machine. I will let you know.

japamac

Level 7

24,400 points

Jan 10, 2013 2:22 AM in response to Luski1

OK. I'm glad that you know.

Kinda' figured that you did (had that air) but thought I'd throw it out there.... 🙂

Your machines behavior is a puzzler. I was even wondering if it were one of the old problem logic boards that never got back to Apple for replacement.

Not sure about the details, exactly, but some FW800 logic boards wouldn't accept CPU transplants properly. They were fab numbers 820-1308, 820-1440, or 820-1445, found by the #5 PCI slot.