I kind of missed the Altair/IMSAI/Cosmac era of early personal computers, I got my first machine in about 1980/81 and ended up owning machines from most of the popular manufacturers that were marketed in the UK (Commodore, Sinclair, Atari, Tandy etc). Still, my favorite was a 'Science Fair Microcomputer Trainer' kit from our local Tandy store. Little more than a TMS-1000 microprocessor and some LEDs and a hex keypad, I learned so much from it. Over the years I broke it and was never able to find another similar substitute. This project is heavily inspired by that TMS computer kit.
Recently (Oct 2017), I became aware I had a limited understanding of what was going on at a lower level in a CPU, how the instruction set was related to the underlying hardware. For example how the instruction decoder could trigger control lines and how the registers and ALU were connected, beyond a very superficial level. I became aware of some free software called Logisim and decided to renew my project by designing my CPU and computer from a 'simulated' lower level.
Current Project Objectives:
- The computer and 8-bit CPU will be designed in Logisim.
- Tools and/or a VM will be created for PC (Linux/Windows).
- The CPU will be implemented in hardware using an Arduino 'host', cased as a standalone computer.