Ubuntu 64bit only sees 2GB out of 8GB RAM on mac pro

Discussion in 'Mac Pro' started by Gomff, Jun 10, 2010.

  1. Gomff macrumors 6502a

    Joined:
    Sep 17, 2009
    #1
    Hi all
    Hope this is the right place for this thread.

    I've recently installed Ubuntu 64 bit on my mac pro (for various reasons) and found that despite having 8GB RAM in the system, Ubuntu only sees 2GB.

    My RAM configuration is 4 sets of 2GB sticks, 2 sticks in each memory board. There's 2GB in the first slots, then nothing in the second, then another 2GB in the third slots, then the fourth is empty. I spaced them out like this in the hope they might stay cooler....Dunno if it works or not. Anyhow, OS X and Windows 7 has no problems accessing all 8GB, it's just Ubuntu that can only see 2.

    Does anyone have any ideas?

    Thanks.
     
  2. Lord Vader macrumors 6502a

    Lord Vader

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    Apr 26, 2010
    Location:
    Death Star
    #2
    Try first and second slot to see if it will change to 4 GB.
     
  3. Gomff thread starter macrumors 6502a

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    Sep 17, 2009
    #3
    Yep, tried that....2 sticks in first 2 DIMM slots on both memory boards and still just get 2 GB showing up.

    Any other ideas?
     
  4. Vylen macrumors 65816

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    Jun 3, 2010
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    Sydney, Australia
  5. Lord Vader macrumors 6502a

    Lord Vader

    Joined:
    Apr 26, 2010
    Location:
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    #5
    32 bit version should see at least 4 GB, right?
     
  6. Lord Vader macrumors 6502a

    Lord Vader

    Joined:
    Apr 26, 2010
    Location:
    Death Star
    #6
    I'm no Linux professional, but simple logical step would be to download different 64 bit Linux distribution.

    For example: http://software.opensuse.org/112/en

    There is live option so you won't have to install anything to test.
     
  7. Gomff thread starter macrumors 6502a

    Joined:
    Sep 17, 2009
    #7
    Thanks everyone for the advice....I've finally got to the bottom of it and feel pretty daft. Despite being certain I'd downloaded the 64 bit version, I was running the 32 bit somehow.

    I then tried to install the 64 bit version which is confusingly labelled AMD 64bit but supposedly works on intel systems as well. This would not boot at all on my system, so I've opted to stay with 32 bit but have installed some pae packages which allow Ubuntu to see all 8GB, so I guess I'm almost where I wanted to be.

    Even with Ubuntu, it seems there's a steep learning curve!
     
  8. DualShock macrumors 6502

    Joined:
    Jun 29, 2008
    #8
    That's because AMD invented the 64 bit standard currently used by AMD and Intel. Intel ripped it off when Itanic went nowhere. Hence, 'AMD64'.
     
  9. Gomff thread starter macrumors 6502a

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    Sep 17, 2009

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