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Annotation of coherent/a/usr/man/COHERENT/fd, revision 1.1.1.1

1.1       root        1: 
                      2: 
                      3: fd                        Device Driver                        fd
                      4: 
                      5: 
                      6: 
                      7: 
                      8: Floppy disk driver
                      9: 
                     10: 
                     11: The files /dev/f* are entries for the diskette drives of COHERENT
                     12: on the IBM AT.  Each entry  is assigned major device number 4, is
                     13: accessed  as  a block-special  device,  and  has a  corresponding
                     14: character-special device entry.
                     15: 
                     16: The device entries are linked to a driver that handles up to four
                     17: 5.25  inch disk  drives,  each in  one of  several formats.   The
                     18: least-significant  four bits  of an  entry's minor  device number
                     19: identify the type  of drive.  The next least-significant two bits
                     20: identify  the drive.   The following  table summarizes  the name,
                     21: minor device  number, sectors  per track, partition  sector size,
                     22: characteristics, and  addressing method for each  device entry of
                     23: floppy disk drive 0.
                     24: 
                     25: 
                     26:      _9 _s_e_c_t_o_r_s/_t_r_a_c_k
                     27: 
                     28:      ff99dd00    4    9   720   DSDD   surface (5.25 inch)
                     29:      ffqqaa00   13    9  1440   DSQD   cylinder (3.25 inch)
                     30:      ff99aa00   12    9   720   DSDD   cylinder (5.25 inch)
                     31: 
                     32: 
                     33: 
                     34:      _1_5 _s_e_c_t_o_r_s/_t_r_a_c_k
                     35: 
                     36:      ffhhaa00   14   15  2400   DSHD   cylinder (5.25 inch)
                     37: 
                     38: 
                     39: 
                     40:      _1_8 _s_e_c_t_o_r_s/_t_r_a_c_k
                     41: 
                     42:      ffvvaa00   15   18  2880   DSHD   cylinder
                     43: 
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                     45: 
                     46: Prefixing an r  to a name given above gives  the name of the cor-
                     47: responding character-device  entry.  Corresponding device entries
                     48: for drives 1, 2, and 3 have minor numbers with offsets of 16, 32,
                     49: and 48 from the minor numbers  given above and have 1, 2, or 3 in
                     50: place of 0 in the names given above.
                     51: 
                     52: For device entries  whose minor number's fourth least-significant
                     53: bit is zero  (minor numbers 0 through 7 for  drive 0), the driver
                     54: uses  surface addressing rather  than cylinder  addressing.  This
                     55: means that it  increments tracks before heads when computing sec-
                     56: tor addresses  and  the first  surface is used  completely before
                     57: the second surface is accessed.  For devices whose minor number's
                     58: fourth least significant bit is 1 (minor numbers 8 through 15 for
                     59: drive 0), the driver uses cylinder addressing.
                     60: 
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                     63: 
                     64: COHERENT Lexicon                                           Page 1
                     65: 
                     66: 
                     67: 
                     68: 
                     69: fd                        Device Driver                        fd
                     70: 
                     71: 
                     72: 
                     73: For  a diskette  to  be accessible  from the  COHERENT system,  a
                     74: device  file  must be  present  in directory  /dev  with the  ap-
                     75: propriate type, major  and minor device numbers, and permissions.
                     76: The command mknod creates a special file for a device.
                     77: 
                     78: ***** Files *****
                     79: 
                     80: <ffddiiooccttll.hh> -- Driver command header file
                     81: /ddeevv/ffdd* -- Block-special files
                     82: /ddeevv/rrffdd* -- Character special files
                     83: 
                     84: ***** See Also *****
                     85: 
                     86: device drivers, fdformat, mkfs, mknod,
                     87: 
                     88: ***** Diagnostics *****
                     89: 
                     90: The driver reports  any error status received from the controller
                     91: and retries the operation  several times before it reports an er-
                     92: ror to the program that initiated an operation.
                     93: 
                     94: ***** Notes *****
                     95: 
                     96: The driver  assumes that the disk is  formatted with eight, nine,
                     97: 15, or 18 sectors of 512 bytes each per track, depending upon the
                     98: /ddeevv entry.  Cylinder addressing is the norm for COHERENT.
                     99: 
                    100: Programs that  use the raw device interface  must read whole sec-
                    101: tors into buffers that do not straddle DMA boundaries.
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                    130: COHERENT Lexicon                                           Page 2
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