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Thread: MacPro RAM

  1. #1
    Join Date
    Jul 2001
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    Confused MacPro RAM

    No big deal here, but wanted to share this with you.
    My 3,1 MacPro came with 2GB of RAM - two 1GB sticks originally supplied by Apple.
    Since then I added 8GB from MacGurus (four 2 GB sticks)
    During last year the original Apple sticks started malfunctioning: sometimes after boot they show 1GB each (correct), other times 512MB each (incorrect) - the total switching back and forth between 9 and 10 GB.
    The MacGurus sticks never failed. Just ordered two more today to replace the ailing ones.

    Puzzle1: how can RAM stick fluctuate from its nominal value to exactly half that?

    Puzzle2: MacGurus says 3,1 will not boot into 64 kernel. Yet much of my Snow Leopard is running at 64 bit (from Activity Monitor). Or does the comment apply only to the original OS: 10.4?

  2. #2
    Join Date
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    Default

    I am led to understand that a MacPro3,1 CAN boot into a 64 bit kernel. (of course, when I wrote that I was following an Apple article that said differently) The current knowledgebase article defining this.

    To boot a 64 bit kernel you need to either hold the 6 and 4 keys down during boot. Or put the following command into your Terminal to make it persistent:

    sudo systemsetup -setkernelbootarchitecture x86_64

    In Snow Leopard you can check whether you are in 64 bit kernel in Profiler under Software. It will state whether 64 bit is running or not.

    Rick
    molṑn labe'
    "I am a mortal enemy to arbitrary government and unlimited power. I am naturally very jealous for the rights and liberties of my country, and the least encroachment of those invaluable privileges is apt to make my blood boil."
--Ben Franklin

  3. #3
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    I have always had good luck with this app It's called StartUp Mode Selector. It has a very simple interface and will tell you what your running and what you are capable of running and let you switch to whichever you want.
    Damien,

  4. #4
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    Default

    Thanks Damien and Rick. Was just curious about the 64 bit comment on Macgurus site. As I recall someone tried to compare speeds with 32 and 64 bit booting, and didn't find anything fantastic; maybe didn't have the software then which can take advantage of 64.

    And of course still curious why a RAM stick can show its full or half capacity, on and off. Oh, I will replace them, but this incident baffled me.
    marrand

  5. #5
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    This is a wild guess based on half remembered info, but aren't dual inline memory modules basically 2 independant memory systems on the same physical stick? If so then one side has failed and you get half capacity
    Damien,

  6. #6
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    RAM - 2 independent memory systems on the same physical stick? I didn't know that.

    Well, that of course would explain reduction by exactly half. Instead of two 1GB sticks, I often read two 512MB sticks. This decrease is random.
    marrand

  7. #7
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    again that is hazy half remembered info don't believe it until someone confirms it
    Damien,

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