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    SubjectRe: floppy programming
    Leandro Bernsmuller wrote:
    >
    > Hi,
    >
    > some body know if exist or is possible to do one
    > driver
    > to makes floppy drive use some type of "balanced" bits
    > distribution?
    > The idea is simple: format a disk doing inner tracks
    > with less bits than
    > in external tracks.
    > Maybe is better think in sectors and not bits
    > banlancing?
    >
    > I want opinions about the idea, pleace.

    Go ahead. Note that ordinary floppies store
    the number of sectors per cylinder in the boot sector,
    and this is used for easy conversion from
    block number (from the fs) to head, cylinder
    & sector (for the hardware driver)

    You'll break this simple scheme, as you'll need
    a table in the driver for how many sectors in track 0,
    how many sectors in track 1, and so on up to
    the maximum track which usually is 80 although
    some floppy drives goes out to 83 or 89 or something.

    >I want opinions about the idea, pleace.
    >
    >Where can I find information about floppy drivers
    >programming, DMA setup,...?

    Look at the existing floppy driver. Note that
    you don't need info on DMA etc., as the driver
    already will do all sorts of weird sector layouts.
    (look at the manpages for superformat)
    The only limitation is that the current driver
    likes to use the same number of sectors per track
    for all cylinders, but you can change that
    using a lookup table.

    I am not sure this will help you though, as
    pc floppies have constant rotational speed
    and I bleieve a constant write rate too.
    So you cannot really squeeze more onto the
    outer tracks without some kind of hardware
    modification.

    Well, maybe your drive
    can gain a little extra on some cylinders if you
    take variable head drag into consideration,
    but you'll surely end up with a floppy that
    fits one drive only if you go too close
    to the rotational tolerances.


    Helge Hafting
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