Why is the Capacity less than advertised?

Discussion in 'iPod touch' started by zerolight, Mar 11, 2008.

  1. zerolight macrumors 6502


    Mar 6, 2006
    I realise that everyone is in the same boat, but why does a 32GB Touch have 29.96GB Capacity? iPods have always been like this, true, but HDDs sizes are generally more fluid, with say an 80GB HDD varying from 75GB to 85GB from manufacturer to manufacturer, so itmakes sens that on such iPods, you see a deviation in actual size. But flash memory is always pretty accurate, certainly to within a few mb. The 2GB difference is pretty shocking... that's space for 10 TV shows, or 350 songs. Why wasn't it called a 30GB Touch, 15GB Touch, and 7.5GB Touch. And how on earth have they managed to lose 2GB from chips that come in multiples of 8GB? Surely impossible?

    Is it something sensible, like they reserve a portion of memory as a swap file? Seems unlikely since it already has 512mb of ram. Or have they just ordered custom flash memory, perhaps in a cheaper non standard size, then rounded it up to a standard size?

    I wouldn't mind so much if all models had lost the same amount - 7.3GB, 15.3GB, 31.3GB. I dunno, seems a bit off.

    Is there a technical reason that Apple have chopped off the capacity? Or is it just cheapness?

  2. andybno1 macrumors 68040


    Nov 6, 2007
    Liverpool, UK
    I'm no technical whizz here but bear with me.

    its not just apple that do this all hard drives advertise one size but the actual amount available is less. The missing space from what I have understood is for when you get corruption on the disk they use part of the missing data to use in its place.......... I may be wrong but that is kinda my understanding of it all
  3. rdowns macrumors Penryn


    Jul 11, 2003
  4. zerolight thread starter macrumors 6502


    Mar 6, 2006
    I agree, makes sense for HDDs. But the touch uses flash memory where the same rules don't apply.

    I guess this kinda applies...

    here is the math
    8 bit = 1 byte
    1 kb = 1024 byte
    1 gb = 1024*1024*1024

    19,709,083,648/(1024*1024*1024) = 18.35551452636719 GB

    18.3 GB
  5. I3eXa macrumors 6502

    Aug 24, 2004
    because you need to 'format' the drive with itunes, disk utility (for hard drives) it creates a reference table if you will and that takes up space. For hard drives on top of that it needs to create a partition and such, and can suck almost 60GB from my western digital 500GB hard drive. That's why everything is listed as 'approximate.'
  6. gnasher729 macrumors P6


    Nov 25, 2005
    See the small print on Apple's web page. 1 GB = 1,000,000,000 bytes. And of course 1 GB is not 1024 * 1024 * 1024 bytes. That is one GiB.
  7. aethelbert macrumors 601

    Jun 1, 2007
    Chicago, IL, USA
    The formatted capacity is proporitionate to the "advertised" capacity. They can't all lose just .7GB. It's not Apple's fault, it's just math.
  8. dejo Moderator


    Staff Member

    Sep 2, 2004
    The Centennial State
    They don't? Why not?
  9. TEG macrumors 604


    Jan 21, 2002
    Langley, Washington
    Advertised Capacity is based on the premise that 1KB = 10^3, 1MB = 10^6, 1GB = 10^9 (which are based on decimal values). Formatted capacity is based on 1KB = 2^10, 1MB = 2^20, 1GB = 2^30. As a result, you still have the same capacity, it is just reported differently. The best solution is to indicate what a formatted capacity is by placing an 'i' inbetween the K/M/G/T and the B to prevent someone from using the SI definations of those letters.

    So KiB, MiB, GiB, etc.

  10. tacofreak macrumors member

    Feb 28, 2008
    Have you ever thought about the memory being used for the apps??? Since its a touch..????????And maybe its being used for newer things like updates with apps?
  11. aidanpendragon macrumors 6502a

    Jul 26, 2005
    There's also an "invisible" ~300MB or so OS partition, apparently. This also comes off the top, before your "available space" stat in iTunes.

    Note that the January applications, at least on Touches where they didn't come standard but were downloaded later, add ~80-100MB to the "Other" stat within available space - i.e., they aren't put into the OS partition.

    If the OP or anyone else has either a 32GB model, or a 8/16GB model that came with the apps as standard, please report on your "Other" size, and your top formatted/available capacity. I'm curious if those that shipped with the apps have a bigger OS partition, or continue putting them in "Other."

    For reference, my Sept/Oct 16GB Touch has 14.84GB total capacity; 18.4MB "Other" under 1.1.2; and ~105MB "Other" under 1.1.4.

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