Many years ago when I was bored I «designed» a fantasy CPU with 6 (six) bits and only one usable register, the accumulator. I thought why not. The result: 18 b

Many years ago when I was bored I «designed» a fantasy CPU with 6 (six) bits and only one usable register, the accumulator. I thought why not. The result: 18 bit address bus 12 bit stack pointer 6 flags zero, negative, carry, overflow, float and user 7 addressing modes accumulator, immediate, absolute, relative, stack, stack without pop, stack special 64 opcodes like NOP, OR, JMP, ROL, STO, ... I discovered that it is well possible to have a 6 bit CPU but of course this is just a game and probably not useful at all. I wonder whether I would be able to create the circuit for the CPU in a simulator. Probably not even if I omit the floating point handling or only if I dedicated about 10 years of free time. I would need to design a microcode or PLA (like MOS 6502, see https://news.ycombinator.com/item?id=5353198 https://news.ycombinator.com/item?id=5353198) system. I find it amusing that this is the one CPU where octal base is really the primary way to display numbers.