NAME
        TD_RAWWRITE/ETD_RAWWRITE -- write raw data to the disk.

   FUNCTION
        This command writes a track of raw data from the provided buffer to
        the specified track on disk. The data is copied straight to the disk
        with no processing done on it. It will appear exactly on the disk as
        it is in the memory buffer, hopefully in a legal MFM format.

        This interface is intended for sophisticated programmers only.
        Amiga reserves the right to make enhancements to the disk
        format in the future. We will provide compatibility via the
        cmd_write and etd_write commands, anyone using td_rawwrite is
        bypassing this upwards compatibility, and may thus stop working.

   IO REQUEST INPUT
        io_Device       preset by the call to opendevice()
        io_Unit         preset by the call to opendevice()
        io_Command      TD_RAWWRITE or ETD_RAWWRITE.
        io_Flags        if the IOTDB_INDEXSYNC bit is set then the driver
                        will make a best effort attempt to start writing
                        from the index mark.  Note that there will be at
                        least some delay, and perhaps a great deal of delay
                        (for example if interrupts have been disabled).
        io_Length       Length of buffer in bytes, with a maximum of 32768
                        bytes.
        io_Data         Pointer to CHIP memory buffer where raw track data is
                        to be taken.
        io_Offset       The number of the track to write to.
        iotd_Count      (ETD_RAWWRITE only) maximum allowable change counter
                        value.

   IO REQUEST RESULT
        io_Error - 0 for success, or an error code as defined in
                   <devices/trackdisk.h>

   NOTES
        The track buffer provided MUST be in CHIP memory

        There is a delay between the index pulse and the start of bits
        going out to the driver (e.g. write gate enabled). This delay
        is in the range of 135-200 microseconds. This delay breaks
        down as follows: 55 microsecs is software interrupt overhead
        (this is the time from interrupt to the write of the DSKLEN
        register). 66 microsecs is one horizontal line delay (remember
        that disk IO is synchronized with agnus' display fetches).
        The last variable (0-65 microsecs) is an additional scan line
        since DSKLEN is poked anywhere in the horizontal line. This leaves
        15 microsecs unaccounted for...  Sigh.

        In short, You will almost never get bits within the first 135
        microseconds of the index pulse, and may not get it until 200
        microseconds. At 4 microsecs/bit, this works out to be between
        4 and 7 bytes of user data of delay.

   BUGS
        This command does not work reliably under versions of Kickstart
        earlier than V36, especially on systems with 1 floppy drive.

   SEE ALSO
        td_rawread