November 4, 1994  by  R. A. Faucett

HOW TO FORMAT A DMF-FORMAT DISK
-------------------------------

Microsoft has begun using an oddball 21-sector format on its
program distribution 3 1/2" floppy disks which they call
High-Density DMF. (Examples are Microsoft Word 6.0c and
Microsoft Excel 5.0c) These DMF-format floppies cannot be
copied or duplicated with any conventional DOS commands; all
you can do is install from them - if the floppies are
trouble-free!

I like to have backup copies of all my original program disks.
I think it's just a wise thing to do. Floppies can go bad
and it's good to have a backup set of original program disks
if they are ever needed. So, the new DMF-format floppies
presented a real challenge in order to make a backup set
of disks.

A nifty little public-domain program, FDFORMAT, lets users
manage DMF-format floppies with ease. Though FDFORMAT and its
associated FDREAD tsr are in the public domain, and no fee is
requested, a thank-you to Christian Hochstatter, the coder
from Marburg, Germany, who developed it, wouldn't hurt. His
postal and e-mail addresses are in the FDFO.ZIP package.

DMF-format disks came along after FDFORMAT was written.
Therefore, FDFORMAT does NOT explicitly support formatting
a DMF disk with its supplied /F parameter options. After a
little experimentation, I found the proper command line
parameters to use in order to format a DMF disk.


The command to format a DMF-format 3 1/2" disk is:

FDFORMAT /T:80 /N:21 /C:4 /D:16 /M:240
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This will yield the following results from FDFORMAT after
the disk is formatted:

        --------------------------------
        OEM-Entry               CH-FOR16
        Total sectors on disk:  3360
        Sectors per track:      21
        Heads:                  2
        Bytes per sector:       512
        Hidden sectors:         0
        Boot-sectors:           1
        Number of FATs:         2
        Sectors per FAT:        3
        Total clusters on disk: 838

          1716224 total bytes on disk
          1716224 bytes available
        --------------------------------

The key is the /M:240 parameter. This sets the Media Descriptor
Byte to F0 (hex). This allows FDFORMAT to successfully use
4 sectors per cluster on a floppy disk. DOS normally supports
only 1 or 2 sectors per cluster as the FDFORMAT documentation
explains. Without this parameter, and using 4 sectors per cluster
(/C:4), FDFORMAT will incorrectly set the Media Descriptor Byte
to F8 (hex) and the disk will NOT be properly read by DOS.


After formatting your DMF-format floppies, the original program
disk files can be copied to the DMF-format backup floppies.

** Be sure to also use the LABEL command to label each backup disk
with the appropriate label from each original disk! **