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    SubjectRe: PROBLEM: KB->KiB, MB -> MiB, ... (IEC 60027-2)
    >>>>> "David" == David Schwartz <> writes:

    David> The way RAM and flash are measured is correct.

    In my experience, RAM and flash *drives* are measured differently.

    I understand that individual flash chips come in powers of 2, but by
    the time they're packaged as a "flash drive", some of that has been
    used up -- yet they're still sold as the full capacity, and the
    manufacturers use the confusion between MiB and MB to defend the

    This "16Mb" drive doesn't really have 16 megabytes of capacity -
    it's really got 15.5. But that's just standard operating procedure
    for storage manufacturers. Non-volatile storage manufacturers,
    including hard drive companies, like to define a megabyte as
    1,000,000 bytes and a gigabyte as 1,000,000,000 bytes. They're
    actually two-to-the-power-of-20 and two-to-the-power-of-30 bytes,
    which is 1,048,576 and 1,073,741,824 bytes respectively. This is
    the main reason why a "20Gb" hard drive won't actually give you
    20Gb of capacity.

    In flash RAM devices, things can get a bit more complex again,
    thanks to the small amount of memory which may be used by the
    device itself for housekeeping. That can vary between device
    families; a CompactFlash card with a given nominal capacity may
    actually have a bit less space than a SmartMedia card with the same
    number on the label. And manufacturers may throw in some more
    memory to push the real capacity up closer to the stated one, which
    is what they've done with the USBDrive. It's still about three per
    cent shy of its claimed capacity, though.


    (E.g., my "512MB" CF card shows up as "487MB" in the camera -- a
    difference of exactly 5%, as would be expected by the MB-vs-MiB scam.
    I'd be happier if the camera said "487MiB", but we're looking at OSes
    we do have control over, not others.)

    And this cheat is getting better (for the seller) with every expansion:

    1 MiB is 5% bigger than 1 MB
    1 GiB is 7% bigger than 1 GB
    1 TiB is 10% bigger than 1 TB

    So when you go out to buy your 1TB drive this year, you're really only
    buying 0.9TiB or so.

    Since all the manufacturers do the same thing, it's possible to
    consider it "fair", at least for comparisons -- but when the customer
    gets home and formats their drive, I think they'd be happier if the
    number was the same as on the carton.

    Just last night I formatted some new "500GB" drives, and they
    eventually came back with 465GB as the displayed capacity. Wouldn't
    it make more sense to display that as "465GiB"?

    David> Talk about a cure worse than the disease! So you're saying that
    David> 256MB flash cards could be advertised as having 268.4MB? A
    David> 512MB RAM stick is mislabelled and could correctly say 536.8MB?
    David> That's just plain craziness.

    No, it sounds like he wants them advertised as 256MB and 512MiB,
    respectively -- packaged flash cards tend to use the 1000 multiples,
    while DRAM uses the 1024. One extra letter doesn't sound all that

    How fast is your Ethernet port? 100Mbps or 95.37Mbps?

    Somewhat archaic now, but how big was your common 3.5" floppy disk (PC
    "HD" format)? It actually used a basis of 1,024,000:

    And if two definitions of the megabyte are not enough, a third
    megabyte of 1 024 000 bytes is the megabyte used to format the
    familiar 90 mm (3 1/2 inch), "1.44 MB" diskette.


    What's likely is that the flash and drive manufacturers will either
    mark their products honestly, or they'll increase the capacity of
    their product to meet the given label.

    (Think about the CRT "diagonal" measurements -- it took a few
    lawsuits, but they eventually switched from measuring bezel-to-bezel,
    or total tube diagonal, to "viewable". Sure, everyone in technology
    "knew" that you had to chop off an inch or two from the advertised
    value to get the viewable; but that's not enough to meet the standard
    of truth in advertising.)

    David> Adopting IEC 60027-2 just replaces a set of well-understood
    David> problems with all new problems.

    Which are clearly solved in the standards document, and remove any
    ambiguity. Is one extra character really that painful to you?


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