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correction - hard drive analysis

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  • B. Degnan
    For the IBM XT you need to use the reference disk to format the hard drive if it s from an alien system. I should have thought of that being an ex IBMer...but
    Message 1 of 3 , Jul 2, 2006
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      For the IBM XT you need to use the reference disk to format the hard drive
      if it's from an alien system. I should have thought of that being an ex
      IBMer...but it's been a while. In the process of formatting a drive now.
      Bill
    • Herb Johnson
      ... drive ... an ex ... now. ... Bill, as I remember XT s and MFM controllers, many of those controllers had a low level format routine in their BIOS ROM.
      Message 2 of 3 , Jul 3, 2006
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        --- In midatlanticretro@yahoogroups.com, "B. Degnan" <billdeg@...> wrote:
        >
        > For the IBM XT you need to use the reference disk to format the hard
        drive
        > if it's from an alien system. I should have thought of that being
        an ex
        > IBMer...but it's been a while. In the process of formatting a drive
        now.
        > Bill
        >
        Bill, as I remember XT's and MFM controllers, many of those
        controllers had a "low level format" routine in their BIOS ROM. That
        routine was accessed by using DEBUG and starting at a ROM address,
        something like C300:0005. A Web search on those terms should find this
        info. POWER THE DRIVE FOR SEVERAL MINUTES before doing this, so it's
        "warm".

        A low level format will rewrite all tracks and sectors. I recommend it
        so that any marginal tracks can be recovered. However this may also
        wipe out any info about "bad" tracks found by previous use.
        Consequently a reasonable next step is to use a program to test and
        mark bad tracks, perhaps the program you mentioned.

        The problem is that relative to drives today, the old MFM drives had
        limited self-diagnostics. Also becuase of their advanced age, they
        will be marginal and have physical errors, probably. For any serious
        use of such drives, they should be reformatted and tested THROUGHLY.

        Can you format under MS-DOS and use on DEC or other OS's? Low level
        formats are not OS dependent; they CAN be controller-dependent. High
        level format which determines drive partitioning IS OS dependent.
        Features like "bad blocks" may or may not be OS dependent. Best
        practice is to low level format and partition on the destination OS
        and controller - but testing on a more demanding controller and OS is
        a good idea!

        Other MARCH associates know more about MFM drives than me and can
        probably advise you, or more likely remind you of tricks you learned
        and forgot.

        Herb Johnson

        Herbert R. Johnson, New Jersey USA
        <a href="http://retrotechnology.com/herbs_stuff/"> web site</a>
        <a href="http://retrotechnology.net/herbs_stuff/"> domain mirror</a>
        my email address: hjohnson AAT retrotechnology DOTT com
        if no reply, try in a few days: herbjohnson ATT comcast DOTT net
        "Herb's Stuff": old Mac, SGI, 8-inch floppy drives
        S-100 IMSAI Altair computers, docs, by "Dr. S-100"
      • Jim Scheef
        Bill, True XT-style controllers had the drive geometry in ROM and thus each controller would only support a very limited number of drives (as many as three -
        Message 3 of 3 , Jul 3, 2006
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          Bill,

          True XT-style controllers had the drive geometry in ROM and thus each controller would only support a very limited number of drives (as many as three - sometimes selected by jumper!). The initial AT controller was a little better in that the drive geometry tables moved to the computer's ROM BIOS. This allowed support for more drives but the tables were obsolete before the first machine was sold. The present situation came about when the BIOS manufacturers realized that a complete table was impossible and allowed for two "user defined" drive types. These are still with us but the BIOS and the drives have become smart enough to fill in the blanks for us.

          So back to your XT era drives... a drive that come up 'bad' simply may not be supported by your controller. I would move to an AT-style motherboard and controller where you can enter the drive geometry into the BIOS settings.

          Herb is correct that most (perhaps all) MFM and RLL controllers had a low level format built into the adapter ROM. I believe this was usually found at C800:xxxx (hey I remembered all this so far). Your favorite search engine, an old book, or some documentation can fill in the exact address, however, once you have the controller talking to the drive with the correct numbers of heads and cylinders, SpinRite will recognize the drive and you're on your way.

          As to moving a drive from one system to another... A fresh low level format (remember when it was the rage to reformat your drive to change the interleave from 3 or 4 to 1?) would erase any remnants of an incomptible partition table.

          Jim

          ----- Original Message ----
          From: Herb Johnson <hjohnson@...>
          To: midatlanticretro@yahoogroups.com
          Sent: Monday, July 3, 2006 11:51:29 AM
          Subject: [midatlanticretro] Re: correction - hard drive analysis

          --- In midatlanticretro@ yahoogroups. com, "B. Degnan" <billdeg@... > wrote:
          >
          > For the IBM XT you need to use the reference disk to format the hard
          drive
          > if it's from an alien system. I should have thought of that being
          an ex
          > IBMer...but it's been a while. In the process of formatting a drive
          now.
          > Bill
          >
          Bill, as I remember XT's and MFM controllers, many of those
          controllers had a "low level format" routine in their BIOS ROM. That
          routine was accessed by using DEBUG and starting at a ROM address,
          something like C300:0005. A Web search on those terms should find this
          info. POWER THE DRIVE FOR SEVERAL MINUTES before doing this, so it's
          "warm".

          A low level format will rewrite all tracks and sectors. I recommend it
          so that any marginal tracks can be recovered. However this may also
          wipe out any info about "bad" tracks found by previous use.
          Consequently a reasonable next step is to use a program to test and
          mark bad tracks, perhaps the program you mentioned.

          The problem is that relative to drives today, the old MFM drives had
          limited self-diagnostics. Also becuase of their advanced age, they
          will be marginal and have physical errors, probably. For any serious
          use of such drives, they should be reformatted and tested THROUGHLY.

          Can you format under MS-DOS and use on DEC or other OS's? Low level
          formats are not OS dependent; they CAN be controller-dependen t. High
          level format which determines drive partitioning IS OS dependent.
          Features like "bad blocks" may or may not be OS dependent. Best
          practice is to low level format and partition on the destination OS
          and controller - but testing on a more demanding controller and OS is
          a good idea!

          Other MARCH associates know more about MFM drives than me and can
          probably advise you, or more likely remind you of tricks you learned
          and forgot.

          Herb Johnson

          Herbert R. Johnson, New Jersey USA
          <a href="http://retrotechnol ogy.com/herbs_ stuff/"> web site</a>
          <a href="http://retrotechnol ogy.net/herbs_ stuff/"> domain mirror</a>
          my email address: hjohnson AAT retrotechnology DOTT com
          if no reply, try in a few days: herbjohnson ATT comcast DOTT net
          "Herb's Stuff": old Mac, SGI, 8-inch floppy drives
          S-100 IMSAI Altair computers, docs, by "Dr. S-100"


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