    Source: FD 179X-01 Floppy Disk Formatter/Controller Family

    IBM 3740 FORMAT

    Track
            Index  Sector
            Mark
    40x  6x         26x    247x
    FF   00  FC     ..     FF

    Sector
    ibyte:        0      1      2       3    4 5
             IDAM Track  Side   Sector  ENC  IDAM           DAM   Data  Data
                  Number Number Number       CRC                        CRC
    26x  6x                                   2x    11x  6x       128x  2x
    FF   00  FE   tn     sin    sen     00   icrc   FF   00  FB   ..    crc

    (1) 128, 256, 512, 1024

    IBM SYSTEM 34 FORMAT

    Track
                Index  Sector
                Mark
    80x 12x 3x          26x    598x
    4E  00  F6  FC      ..     4E

    Sector
    ibyte:         0      1      2      3    4 5
             IDAM  Track  Side   Sector ENC  IDAM               DAM  Data  Data
                   Number Number Number      CRC                           CRC
    12x  3x                                  2x    22x 12x  3x             2x   54x
    00   F5  FE    tn     sin    sen    01   F7    4E  00   F5  FB   256x  crc  4E

    (2) 128, 256, 512, 1024