G5 256mb ram sticks not recognized

Discussion in 'PowerPC Macs' started by jwjsr, Oct 30, 2012.

  1. macrumors 6502


    Mar 15, 2012
    Fairhope, Alabama
    Why did I lose .5gb? Memory was 2.5gb as shown below. Then I popped in 2 more 1gb sticks for a total of 4.5 gb and now it shows 4gb instead of 4.5gb. It no longer recognizes the .5gb in J11 and J12.

    Before adding another pair of 1gb sticks--

    Hardware Overview:

    Model Name: Power Mac G5
    Model Identifier: PowerMac7,3
    Processor Name: PowerPC G5 (2.2)
    Processor Speed: 2 GHz
    Number Of CPUs: 2
    L2 Cache (per CPU): 512 KB
    Memory: 2.5 GB
    Bus Speed: 1 GHz
    Boot ROM Version: 5.1.8f7
    Serial Number (system): RM428ZHSQPM
    Hardware UUID: 00000000-0000-1000-8000-000A95D4C0D2
  2. macrumors regular

    Aug 1, 2009
    Probably a compatibility issue, either the type of ram or because of the size of the ram and the way the mac buss is addressing it.
  3. macrumors 65816


    Dec 18, 2010
    If that's the PCI version it can only take a maximum of 4GB. The PCI-X version can take 8GB. If it has 4 RAM slots, it is the PCI version, if it has 8 slots, it's the PCI-X version. They both have the same model identifier number, PowerMac7,3.
  4. thread starter macrumors 6502


    Mar 15, 2012
    Fairhope, Alabama
    To clarify, I did not touch the 4 sticks compromisising 2.5 gb, only after I added the 2 1gb sticks did it stop recognizing the 2 256mg sticks, mine is thePCI-X
  5. Guest

    May 29, 2012
    I had a similar issue but after much trial and error realised the sticks had to be placed in certain slots (no doubt how the dual channel works) which I wrongly assumed was next to each other. Mine is a Late 2005 G5 DC 2.3.

    I have two bank of 4 slots.
    Each slot has a number (1-4 on both banks)
    When adding memory in pairs they must be added as follows :-

    Bank 1 Slot 1
    Bank 2 Slot 1
    Bank 1 Slot 2
    Bank 2 Slot 2
    etc etc

    I added RAM recently by just putting them in the next two available slots and had less than before - took me a while with a torch and trial and error to work out what was happening...
  6. thread starter macrumors 6502


    Mar 15, 2012
    Fairhope, Alabama
    Well, it dosen't make a lot of sense but I fixed by moving the 2 original 256mb sticks to the third slots of each bank, and moving my 2 1gb sticks to the 1 -or inside slot of each bank
  7. macrumors newbie

    Oct 16, 2012
    Winnipeg, MB, Canada
    Glad to hear you figured it out. I am having the same issue with mine. But keep an eye on it. I did manage to figure out how to get it to recognize the extra ram in my PM G5 but it lead to random crashes and random ram sticks failing during the boot diagnostic and the amount of ram the computer recognized kept changing. I think the fact that I am using several different brands and they are not all the same size even though they are matched pairs so I am still working things out on mine. I hope you don't run into the stability issues I did. I am back to it only recognizing 2gbs after some re-arranging but at least the computer is stable now.

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