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Thread: Memory query - 16gig machines shows 15.7 in Ubuntu 12.04

  1. #1
    Join Date
    Nov 2006
    Beans
    35

    Memory query - 16gig machines shows 15.7 in Ubuntu 12.04

    Hi everyone,

    I have a 16gig RAM systems that under Windows is listed as 16gig but under Ubuntu is listed as 15.7 gig machine. I am guessing the OS is pinching 300mb for a crash kernel or similar but I would really like to know for sure from the experts

    As an experiment I created a 8gig Ubuntu 13.x machine in Virtualbox that listed itself as 7.8gig so I am guessing there is a logical explanation rather than hardware fault

    Brilliant OS by the way, I've been using Ubuntu now as my sole OS for over a year, and made a donation accordingly on downloading the latest 12.04 ISO for my new build.

    Thank you in advanced,

    Adrian

  2. #2
    Join Date
    Nov 2006
    Beans
    35

    Re: Memory query - 16gig machines shows 15.7 in Ubuntu 12.04

    free -m

    total used free shared buffers cached
    Mem: 16048 1276 14772 0 34 452
    -/+ buffers/cache: 788 15259
    Swap: 16379 0 16379

    I believe 16 gig of RAM is 16384mb

  3. #3
    Join Date
    Nov 2007
    Location
    London, England
    Beans
    5,793
    Distro
    Xubuntu 15.04 Vivid Vervet

    Re: Memory query - 16gig machines shows 15.7 in Ubuntu 12.04

    I have read before (can't remember where) that free doesn't list the memory occupied by the kernel, and as such will always show around 300M less than is physically present (it can never be free).

  4. #4
    Join Date
    Jan 2009
    Location
    ::1
    Beans
    2,481

    Re: Memory query - 16gig machines shows 15.7 in Ubuntu 12.04

    If you want to see the RAM that Windows is reporting, do this:

    Code:
    sudo dmidecode | egrep -A8 -i -e "Memory Device" | grep -i MB | grep -vi range
    Example:
    Code:
    $ sudo dmidecode | egrep -A8 -i -e "Memory Device" | grep -i MB | grep -vi range
    	Size: 2048 MB
    	Size: 2048 MB
    HTH

  5. #5
    Join Date
    Sep 2013
    Beans
    28

    Re: Memory query - 16gig machines shows 15.7 in Ubuntu 12.04

    Well I have 4 gig ram and it says i have 3.2 gigs because my system has dedicated some to graphics, and other, etc
    HP Workstation xw6000
    4GB ram
    80GB + 250GB Western Digital Caviars
    2x Intel Xeon @ 2.66GHz

  6. #6
    Join Date
    Nov 2006
    Beans
    35

    Re: Memory query - 16gig machines shows 15.7 in Ubuntu 12.04

    Hi everyone,

    In the first instance, many many thanks for taking time to reply I really appreciate it!!

    I agree with everyone above that this is standard Linux behaviour as today on a really big machine, I created a virtual machine with 16384mb then ran Ubuntu from the live CD and again it reported the machine as having 15.7gig. I am relieved, it means my hardware is ok

    Thank you everyone - I bet the kernel has it!

    Adrian

  7. #7
    Join Date
    Apr 2011
    Location
    Maryland
    Beans
    1,461
    Distro
    Kubuntu 12.04 Precise Pangolin

    Re: Memory query - 16gig machines shows 15.7 in Ubuntu 12.04

    Color me learned! I never realize that the system did this, and just assumed that what it needed would show up in as buffered memory. Sure enough, though, it's true:

    Code:
    $ free -m
                 total       used       free     shared    buffers     cached
    Mem:         32151      31372        778          0       3122      23967
    -/+ buffers/cache:       4282      27868
    Swap:        15258          0      15258
    
    $ bc <<<32*1024
    32768
    This is good to know for future reference!

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