fd(7)                                                                 fd(7)


   NAME
         fd - floppy disk interface

   DESCRIPTION
         fd provides the interface to both 3" and 51/4" floppy disk units
         connected to a Western Digital 1772 controller.  The character and
         block special interfaces in /dev provide support for up to two drives
         using 512 byte sector sizes.  Other sector sizes are supported via
         the PDSET ioctl.

         The binary representation of the minor device number is encoded as
         cudhspppp; meanings of which are as follows:

         c     Selects configuration on open. A 0 in this position means that
               the disk drive parameters will be set as indicated by the d, h,
               and s bits. A 1 here means that the parameters last used will
               be re-used.

         u     Selects which floppy drive to use.

         d     Selects density; 0 = double density (9 sectors/track), 1 = quad
               density (18 sectors/track).  Quad density may not be selected
               unless the motherboard switches have been set so as to indicate
               that a drive capable of quad density has been installed.

         h     Selects number of sides (heads); 0 = single sided, 1 = double
               sided.

         s     Determines whether to do double stepping; 0 = no, 1 = yes.
               Setting s to 1 enables 40 track/inch disks to be read.

         pppp  Must be zero.

         Both block and character (raw) interfaces are provided.  The block
         interface accesses the disk via the system's normal buffering
         mechanism and may be read or written without regard to physical disk
         records.

         The raw interface provides for direct transmission between the disk
         and the user's data area; thus I/O is considerably more efficient
         when large amounts of data are to be transferred.  However, seeks are
         truncated to 512-byte block boundaries and attempts to write data in
         quantities that are not in multiples of 512 bytes will fail,
         returning an error condition.

         Internally, fd uses a pdsector structure and a structure of type vtoc
         (both as defined in /usr/include/sys/vtoc.h) to store certain
         information relating to the physical characteristics of each drive.
         (Note, however, that pdsectors and vtocs are not implemented on the
         floppy disk itself.)



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   fd(7)                                                                 fd(7)


         The following extra fields (as defined in /usr/include/sys/fd.h) are
         implemented in the pdsector.

         #define pddensity  reserved[0]
         #define pdprecomp  reserved[1]
         #define pdsteprate reserved[2]

         These fields have meanings as follows:

         pddensity
               Indicates the disks recording density.  Possible values
               (defined in /usr/include/sys/wd1772.h) are DD for double
               density (9 sectors/track) or QD for quad density (18
               sectors/track).

         pdprecomp
               First track not to apply precomp.  The default value is zero
               (i.e., precomp always on).

         pdsteprate
               Time for the heads to move between tracks.

         These parameters may be changed via the PDSET ioctl function.

   FORMATTING
         The low level, device specific format program may be used to format
         new diskettes or simply reconfigure the driver in a variety of ways.

         When something other than the standard parameters are required, a
         data file must be supplied to the format program. The following
         options may be set in the data file:

         allocend

         allocstart

         bytespersector(*)
               This may be set to 128, 256, 512, or 1024.

         cylinders(*)
               This may be set to any number in the range 0 < n <= 82.

         defectmap

         density(*)
               This may be set to DD or QD.

         devicetype





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   fd(7)                                                                 fd(7)


         diagnostinfoblock

         diagnostsize

         errlogarea

         heads(*)
               This may only be set to 1 or 2.

         interleave(*)

         logicalsectorzero

         mfginfo

         nextrelocationarea

         noofrelocationareas

         precomp(*)

         relocationarea

         sanity

         sectorspertrack(*)

         serial

         sizeofdefectmap

         sizeoferrlogarea

         sizeofmfginfo

         sizeofrelocationarea

         steprate(*)

         version

         Only those option marked with (*) are used by the driver, other
         options may be set, but changing them will have no effect.

   FILES
         /dev/fdsk/*
         /dev/rfdsk/*

   SEE ALSO
         format(1M), disk(7).



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