This board with a handful of chips serves as control interface between Calculating Core (ALU/RegFile assembly) and the rest of CPU. 

It mostly does decoding of ALU instructions into ALU control signals, constant value, and register addresses. It also takes in ~R, clk, and a couple of control signals from Control Unit (yet to be developed) and distributes them to Calculating Core accordingly.

Here is the board:

And here are a couple views of testing process for the whole calculating core: