Hardware Design through
High-Level Functional Components

The most well-known are the Register Transfer Modules by Gordon Bell et al. at CMU, which begat the PDP-16 product line from DEC. I heard that there was a PDP-16 system in the U. of Delaware security office, but I don't think I ever saw it.

An earlier one (1966) was the set of Macromodules by Wesley Clark, who had previously designed the LINC.

Another one was the Universal Control Module by Dr. David M. Robinson at the U. of Delaware. It focused on the control structure, leaving simplification of the data structure to off-the-shelf MSI TTL chips. One of the things that were built with UCMs was a music box (by Steve O'Brien?) which was attached to a serial port of a PDP-11.

An effort was made (in 1973?) to get semiconductor manufacturers to produce ICs of these modules, but the manufacturers weren't interested. While the other modules would have required an entire new series of chips, the UCM would have required only 1 new chip type, which would have a modest transistor count, and would have fit in well with the standard series of chips. The semiconductor companies weren't interested because, as it turned out, they were busy preparing for the advent of microprocessors, which, in retrospect, were far more useful chips.

This description of PMS Notation has an interesting definition of what a computer is.