With some of the basics out of the way, I think I can now deal with an initial instruction set for the computer. I plan to do a somewhat minimal instruction set, but I do not think I will be able to keep it at less than 32 instructions as 'Minimal Instruction Set Computing' requires.
So, I've gotten me a few books on processor design, from the ground up.
One is a first edition of 'Digital Computer Electronics' by Albert Paul Malvino and Jerald A. Brown from 1977. The second one is 'The Elements of Computing Systems: Building a Modern Computer from First Principles' by Noam Nisan and Shimon Schocken from 2005.
So, I have shared this project on a few Discord servers now and taken some criticism, especially for my memory considerations. And now that I've slept over that criticism and been at work thinking, I have to admit that some of my originally planned features are, well, feature creep.
After putting down the initial design for the ALU, I believe that its time to consider how to organise the memory of the system. Especially in view of the design goal of using a RAM based register-to-register design, like it was used in the Texas Instruments TMS9900, which itself was a single chip implementation of TI's TI-990.
You will certainly now ask, 'Why are you already jumping to the ALU?' Because my brain wants to take care of the ALU first, largely for reasons of interest. Besides, having a design of the ALU allows me to have an idea what operations it can do, once I go for creating the instruction set.