One of the very first technical books I ever bought was “Programming the Z80” by Rodney Zaks. This was because my parents had bought me a Sinclair ZX81 computer, powered by a Z80. In the event I never did do any assembly language programming on the ZX81 (which could only be done by POKE’ing numeric values into memory locations anyway) but I did read the book from cover to cover a couple of times because I really wanted to understand how computers actually worked. I soon started at university and although I had a great time I do now rather regret not making the most of my opportunities. In particular I had pretty much free access to some really well equipped electronics labs. True, I didn’t have much money for components but there was work available and I’m sure l could have earned something!

The original cover image

So bringing those things together I wanted to investigate a bit of alternative history and consider what I night have been to create back then. Could I build a simple computer around a Z80 CPU?

I realise that I could use something like an Arduino, which, despite being a full 32 bits, has some similar restrictions in terms of ROM, RAM and I/O facilities. That is however, just a bit too easy it is, after all a “system on a chip” so there is no hardware development to be done. I think it might be fun to design and build my own hardware around a Z80, adding ROM, RAM and whatever other support logic and peripherals I night need and develop some simple programs in a combination of ‘C’ and assembler. I should also restrict myself to largely using as reference sources the books and data sheets that were available in the 1980s, and which are now freely available on, including the Zaks book mentioned above.

I’m going to document progress in blog posts and on this page you will the consolidated list…