Changes
/* FDC Track Format */
* the 765 has 5 status registers, while the 179x only has one.
* the 765 has 3 scan commands, while the 179x has none.
* the 765 has drive select pins to directly select one of four floppy drives, while the 179x has none. Instead, external logic must be used to handle multiple drives.
* the 765 only does standard track formats (preamble, marks and data fields), while the 179x will write anything you tell it in the write track (formatting a track) mode.
