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Thread: Hard Sector Floppy: Revisited

  1. #1
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    Default Hard Sector Floppy: Revisited

    Hello Folks,

    Being a fan of obsolete technologies, I would like to know about
    problems with the hard sector floppies. They had their own
    simplicity!

    ziloo

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    The biggest problem is finding enough media to make a system useful. Mike Douglas has a very useful little board that generates correctly timed hard sector pulses for soft-sector media:

    http://deramp.com/vsg.htm

    I've got one for my North Star MDS single-density system, which works fine.

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    Thank you glitch for your response!

    What I meant was: at the time of its use...back when....what were
    the problems/shortcomings of the hard sector disk?

    ziloo

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    Quote Originally Posted by ziloo View Post
    Thank you glitch for your response!

    What I meant was: at the time of its use...back when....what were
    the problems/shortcomings of the hard sector disk?

    ziloo
    Shortcomings.
    1) Had to buy the matching hard sector disk for the drive purchased. Expensive. There were multiple designs of hard sector disks with different numbers of sectors and, in the 8" models, different placement of sector holes.
    2) Limited storage capacity.
    3) Very inflexible format.

    Advantage:
    With the extra holes signaling the start of a sector, the drive motor did not have to be able to maintain the exact rotation rate range needed to do soft sector formats.

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    A little background...

    The first floppies were, in fact, hard-sector--they had a sector hole punched at the beginning ef each sector. All you needed to locate a sector was a counter that was reset every time the index passed by. You included enough of a preamble to sync up the data separator circuitry and bob's your uncle. Soft-sectoring, on the other hand requires that special synchronization and ID fields be included before each sector's data, which, of necessity requires more complicated electronics. You also need to leave sufficient gap or "splice" postamble to take into account any speed variation between drives.

    8" HS floppies are all 32-sector, but for some very early Memorex and IBM ones that were 8 sector, with the sector holes punched on the outer area of the cookie.

    If you want fewer sectors for longer data blocks you can divide the sector pulses by 2, 4, 8... But that's it.

    5.25" HS floppies are a little strange--they come in both 10 and 16 sector configurations and the two are not interchangeable.

    Basically, the hard-sector floppy affords a higher sector packing density with simpler electronics than soft-sectoring, but is more expensive to produce--and is not very flexible in terms of format. Not that hard-sector hardware implementation ensures any interchangeability--there are about as many schemes as there are manufacturers. The end of hard-sectoring gradually happened when IBM standardized on soft-sector media with the 3740 and System/3 floppies.

    I do recall that early LSI soft-sector controller ICs were very expensive--but again, silicon is cheap and keeps getting cheaper for a given functionality, so that consideration disappeared also.

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    Thank you kerbizfan and Chuck for the thorough explanations!

    Some people have made a jig sort of set-up for
    punching precise holes in soft sector floppies to
    make their own hard sector ones.

    ziloo

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    If you've got a drive that's reasonably stable in terms of RPM (e.g., a 3.5" drive), you can synthesize the sector pulses using a small MCU. I suspect that a more accurate version could use a photocell and markings on the drive hub mechanism, but that would entail modifying the drive.

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    Does anybody have a picture of an actual hard sector floppy?

    ziloo

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    What size? Really, it's hard to tell the difference, but for the label.

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    Quote Originally Posted by Chuck(G) View Post
    ..........it's hard to tell the difference, but for the label.
    so the holes must be very small?

    ziloo

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