INT 13h,  07h (7)        Format Disk Starting at Cylinder          fixed disk

    Initializes each sector on a specified cylinder and all subsequent
    cylinders with sector address and size information. Only XTs may use
    this service.

       On entry:      AH         07h
                      AL         Interleave value
                      CH         Cylinder number (10-bit value; upper 2 bits
                                 in CL)
                      DL         Drive number (Bit 7 must be set)

       Returns:       AH         Status of operation (See Service 01h)
                      CF         Set if error, else cleared

  --------------------------------------------------------------------------

       Notes:         This service will destroy all previous contents of
                      the disk.

                      The cylinder number is a ten-bit quantity (0 through
                      1023). Its most significant two bits are in bits 7
                      and 6 of CL; the remaining eight bits are in CH.

                      If an error is encountered, use Service 0h to reset
                      the drive and retry the operation.