1984. Successor of the /23. At that time the components were VLSI, and these -11's were marketed as MicroPDP's (this has in fact begun with the /23). The /73 had a 15MHz J-11 CPU with 22-bit memory management for the 4MB RAM max. Just to make life more complicated, 18 MHz /83 CPU boards can also be found in /73 systems, as a /83 CPU (M3190-A[DE]) with qbus memory (instead of the PMI (private memory interconnect) memory used in those systems) is called a /73... 

There was no UNIBUS equivalent.

The J-11 was manufactured by Harris Semiconductors, and it hasn't been fully completed, it lacked the WCS and CIS options. 

A very popular enclosure is displayed to the left: this was the BA23 standing tower configuration, that had place for a 8x4 backplane, an RX50 floppy or TK50 streaming tape drive and an RDxx harddisk. The BA23 could also be rack-mounted.

An OEM /73
KDJ11-A CPU card