FD1793 Western Digital Disk Controller

The FD179X (X=1,2,3,4,5,7) can be considered the end result of both the FD177X and 178X designs. In order to maintain compatibility, the FD177X, FD178X and FD179X were made as close as possible with the instruction set and I/O registers being identical. The 1793 is identical to the 1791 except the Data Access Lines are TRUE (for systems that utilize true data buses). The 1792 and 1794 are "single density only" versions of the 1791 and 1793 respectively. The 1795/7 has a side select output for controlling double sided drives.