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  1. #1


    Member Since
    Oct 16, 2009
    Posts
    15
    Drives have different sizes on dif OS's. Why?
    Hello folks,
    I hope this is in the right forum heading.
    I will start with the setup.
    I have 2 drives hooked up to an Airport Extreme.
    I have 1 MacBook 10.6.2, 1 iMac 10.3.9 and 1 PC XP accessing the drives through the network.
    Drive 1 is a WD elements. 640gb
    On the PC it shows as total size 596gb
    On the MacBook it shows as total size 640gb
    On the iMac it shows as total size 596gb

    Drive 2 is in an iomega case. 20gb
    On the PC it shows as total size 18.9gb
    On the MacBook it shows as total size 20.35gb
    On the iMac it shows as total size 18.9gb

    Have apple changed the formula for the way it reads the size of drives? And is this why when everyone who installed 10.6 saw their drive space increased?

    Any thoughts?

  2. #2

    vansmith's Avatar
    Member Since
    Oct 19, 2008
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    2012 13" MBP (2.5 i5, 8GB)
    Quote Originally Posted by nevyn68 View Post
    Have apple changed the formula for the way it reads the size of drives?
    Yes they have. Windows and OS X pre-10.6 measure hard drive space using base 2 notation (1MB = 1,024KB) while OS X 10.6 and HD manufacturers use base 10 notation (1MB = 1,000KB). This is why your HD shows up as "the correct size" in Snow Leopard. My 320GB HD is reported to be 319.73GB while in Leopard, it was ~298 (I think).
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  3. #3

    Slydude's Avatar
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    Specs:
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    This was indeed changed for Snow Leopard. Drive manufacturers report their drive capacities in base 10 (the numbers we are all familiar with). Until Snow Leopard the OS reported drive capacities in Binary (base 2). The resulting "loss" of size is due to differences in these number systems. One GB binary is not exactly the same as one GB decimal. Windows is still using base 2 unless that changed with Win 7. How Mac OS X reports drive capacity
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  4. #4


    Member Since
    Oct 16, 2009
    Posts
    15
    Thanks folks

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