Been playing around more with logic and hardware design and im realising that this is going to be a lot of parts so im going to try and skimp a bit to try and get a running prototype in months vs years

im going to use a single bit ALU and have been playing with designing my own. the following is my own creation with no outside information other than the full adder gates. (i think it uses 44 transistors, and has 11 gate delays worst case)
it has 3 flag outputs
A>B
A=B
A<B

8 inputs (could shave off 3 with a mux) [bit A, bit B, carry in, AandB, AorB, AxorB, AaddB, notOut]

notOut inverts the result of all 4 AfxB inputs allowing for Nand, Nor and Xnor

trying to make a list of all functions i want to implement in the alu so let me know if you have any suggestions

Can I go full-on retro and recommend a book from 1953? It's "Faster than thought" by B. V. Bowden... the middle section is a chapter for each of the machines then current in the UK (and a bonus chapter for America), the first chapter is a history but chapters 2 and 3 are about how the machines of the day worked. These were bit-serial machines and you might find it interesting reading - they had limited resources much as you do. The final section is on applications of computers.

Read online:
https://archive.org/stream/FasterThanTh ... 9/mode/1up

PDF is 40Mb:
https://archive.org/download/FasterThan ... t_text.pdf

Much less retro is a very interesting book from the late 70s about chip design, which was one of my textbooks in the early 80s. It covers the technology and builds up to a two-chip 16 bit CPU. It's online free as a large PDF. Mead and Conway's "Introduction to VLSI Systems". Chapter 5 at page 269 contains the ALU discussion:
http://ai.eecs.umich.edu/people/conway/ ... f#page=269
Just chapter 5:
http://ai.eecs.umich.edu/people/conway/ ... Ch5-2s.pdf
Parent page:
http://ai.eecs.umich.edu/people/conway/ ... links.html