I have been thinking a lot about wiring the instruction logic and have started with getting the ALU and PC to work with each other. The MUX and DMUX are working as planned except that the PC out to the MUX needs four additional buffer gates to get the signal level correct. I had the same issue with the ALU some time back and buffers took care of the signal level so will do the same for the PC. The PC register is made up of pnp transistors and was the first register that actually worked for me :-)

A bank of switches is being used to select the active portions of the MUX and DMUX so that with that bank plus the front panel input switches, I should be able to test out what steps are going to be needed for dealing with the instruction logic.

Oh Boy, this is soooooo much fun :-D

Just to think that most of the wiring is in my head and not on paper :-O