The ALU is tested and other units have been written.
I have implemented a small barrel shifter/rotater, with 2 versions, one is smaller, the other is faster. Now all 12 ALU opcodes are covered.
I have also implemented the MUX-based register set, with 2 versions : the first is a classical tree (like I implemented for the #Numitron Hexadecimal display module ) with a fanout of 8-24 for the address lines. The second is more sophisticated, with 3 interleaved trees, with a fanout of 20-18-18, close to the theoretical 18.6 !
All units have their own small testbench in their own directory. I will write the rest very soon.
And now, an incrementer. I'm moving to the I/O system.