The following is an exerpt from a text file written/complied by one
A.D. Longton of Rockville, MD. I have omitted the discussion of how
to make a 1.44M disk from a 720K disk with a soldering iron since I
don't want to be a party to furthering that practice. I did, however,
find the remainder of the information quite interesting and have 
included it here. As You can see, it comes directly from the 
'brain trust' at Big Blue and may tend to lend some measure of credibility
to what I've been saying all along. The original file was dated 5/10/89,
I'm not sure when the information spewed forth from Boca Raton.
-[Steve]- (tm)

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                           3.5" DISKETTE FORMATS
                                Kevin Maier
                              IBM Corporation
                            Boca Raton, Florida
                      "Reprinted by permission of the
                  IBM Personal Systems Technical Journal."
                           Page 42, issue 2, 1989

     "The  original recommendations about the proper formatting and use
     of  PS/2 diskettes have undergone revision.  This article explains
     why the recommendations have changed.

                            THE ORIGINAL CAUTION

     Personal  System/2 shipping cartons include a sheet of paper  that
     cautions  users not to format a 2.0 MB diskette to 720 KB, because
     the diskette becomes unusable and should be discarded.

     This  caution was issued because of the physical properties of 720
     KB  diskettes versus 1.44 MB diskettes.  The 720 KB format uses  a
     higher  write current, and the  1.44 MB format uses a lower  write
     current.   To  accommodate  the  higher write current,  the  oxide
     coating on a 1.0 MB (720 KB formatted) diskette is denser than the
     oxide coating on a 2.0 MB (1.44 MB formatted) diskette.

     When  you format a 2.0 MB diskette to 720 KB, you apply the higher
     write  current  to  the  less dense oxide coating.   The  hardware
     developers  originally felt that this meant the 720 KB  formatting
     pattern  is  written too  deeply  into the 2.0 MB  oxide  coating,
     causing intermittent data errors and unreliable use.  Furthermore,
     the developers felt that if you attempted to reformat the diskette
     to 1.44 MB, which uses the lower write current, the 1.44 MB format
     would  not  completely  write  over  the "deeper" 720  KB  format.
     Therefore  the developers' recommendation was to discard a 2.0  MB
     diskette that was formatted to 720 KB.

                          THE SUBSEQUENT FINDINGS
                             [aka a RETRACTION]

     Since  the time that this caution was issued, the developers  have
     performed  additional testing, and have concluded that there is no
     need to discard a 2.0 MB diskette that was formatted to 720 KB.

     It  is still true that a  2.0 MB diskette formated to 720 KB  will
     cause intermittent data errors.  However, the latest assessment is
     that  you will be able to reformat the diskette to 1.44 MB and use
     it reliably after that.

     The  same logic applies to a 1.0 MB diskette formatted to 1.44 MB.
     You cannot use it with the 1.44 MB format, but you can reformat it
     to 720 KB and use it reliably after that.

     Therefore,   the  current  recommendation  is:  If  you  format  a
     diskettte  to  the  wrong  capacity, do not discard  it;  instead,
     reformat it correctly and use it."


     With  all those feelings  and recomendations on those feelings  it
     makes  me wonder how much experimentation was actually being  done
     on  a  strictly scientific level.   Note that the one  mention  of
     formatting  1.0mb disks to 1.44 MB does not say that you will  get
     errors  if you use them.  What it does say is that if you reformat
     that  wrongly formatted disk, you can reliably use it at 720  KB.
     The  implication is that since there were errors with 2.0mb  disks
     formatted  to 720 KB "logic applies" that there will be errors  if
     the  reverse is done.  This is not necessarly the case, and we are
     not told why, we are just told.

     FYI, here are the specifications for the 720 KB, 1.44 MB, and 360k
     5.25"  disk  drives  as  listed  in the same issue on pages 43-44.
     Note the large similarity between 360k and 720 KB disks and 720 KB
     disks and 1.44 MB disks.

                     720 KB and 1.44 MB Diskette Drives

                                  720 KB     1.44 MB     360 KB (5.25")
     Access time:
          Track-to-track            6 ms        6 ms       6 ms
          Head settle time         15 ms       15 ms      15 ms
          Motor start time        500 ms      500 ms     750 ms^

     Disk rotational speed:       300 rpm     300 rpm    300 rpm
          Maximum Latency         200 ms      200 ms     200 ms
     Formatted Characteristics:   720 KB     1.44 MB^    360 KB^
          Tracks (actual)          80          80         40   ^
          Tracks per inch         135 tpi     135 tpi     48   ^
          Sectors per track         9          18   ^      9
          Bytes per sector        512         512        512
          Bytes per track        4608        9216   ^   4608
          Data heads                2           2          2
          Sector interleave factor  1:1         1:1        1:1
          Sector skew factor        0           0          0
          Sectors per cluster       2           1   ^      2

     Transfer rate            250,000     500,000^   250,000
     (bits per second)

     (All ^'ed numbers are numbers that are different from the 720 KB
     format.)

             "...if they think you're technical, go crude. ....
         These days, though, you have to be pretty technical before
                     you can even aspire to crudeness."

                           --From William Gibson's short story
                             Johnny Mnemonic
