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False capacity of Hard disk !

  1. Sep 18, 2003 #1
    40GB? 60GB? 80GB?
    I long time ago had found that the hard drive i bought contains less space that what it claims.
    look at this:

    Are we cheated by the manufacturers?
  2. jcsd
  3. Sep 18, 2003 #2
    Well, it depends on what base you are using to count with, base 2 or base 10.
  4. Sep 18, 2003 #3
    The change comes when the disk is formatted for use by the operating system, I'm not exactly sure why, but I hard drive will come up as 20 GB, but once a formatting system is put on the disk, that would, I assume take up some of the space and leave less space for the usuable information.
  5. Sep 20, 2003 #4


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    Staff: Mentor

    To expand, when using base-2, a kilobyte is 2^10 or 1024 bytes. Same rules for mega and giga. Hard drive manufacturers for some reason (marketing?) all use the standard base-10: 1,000 bytes per kilobyte. When hard drives were a couple of hundred megabytes, the math didn't make too much of a difference. Today, a 100 gigabyte hard drive actually has 100,000,000,000/1024/1024/1024=93.1GB of real capacity.
  6. Sep 23, 2003 #5


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    Science Advisor

    Its the same thing when you buy a car stereo amplifier. The wattage power in big type on the front is the peak power, or the maximum that it can perform. Your RMS power is actually what is important.

    Same deal, slightly different. The advertisement departments are behind this one I'd bet. They could sale you a 93.1gb hd, and tell you its that size, but for one, it would take steps in confusing the general publix, and 2, switching notations and saying its bigger means a larger pricetag.

    I suppose that its getting out of hand with the current sizes, but I've learned that pretty much anything is not what it seems.
  7. Oct 8, 2003 #6
    this figure is arrived at by the manufacturer by multiplying the total numbers as follows: tracks x sectors/track x bytes/sector x number of heads, or for drives larger than 8.4 Gb it is calculated as the number of addressable sectors x 512 bytes/sector. when the drive is detected & configured by the system's BIOS and then partitioned, it shows it to be less. remember 1 Mb = 1024 Kb. the manufacturer's rating is derived by using the Fdisk size x 1.07 (for drives >1 Gb) or by using the Fdisk size x 1.05 (for drives <1 Gb).

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