I've been long thinking about creating my own personal computer as if the IBM PC never happened and i want to be the "one-man-band" creating everything from hardware to software. I just feel that this is a journey i want to go through and experience.

For long time (and slightly even today) i've been thinking whether it should be Z80 or 6502 based machine. The beauty if 6502 is extreme simplicity, while Z80 can do some neat tricks. (Like LDIR instruction for example) Z80 also has CP/M already present, if i ever want to go that route.

Then i found the Olimex Neo6502: https://www.olimex.com/Products/Retro-Compute … source-hardware
And what i saw was that it is basically just 2 components: 6502 as retro CPU + RP2040 as "software defined machine". Basically all pins from 6502 connect to RP2040 and so you can emulate whatever peripherals in software inside RP2040.

As it does bring out all 6502 pins to a header, you can gradually bring different parts of devices out from software into real-world hardware, until there's nothing left in the RP2040.

It looks like this is exactly what i would need to start building my machine. I'm a software engineer, so starting with hardware that is defined in software definitely helps to start with the project. I have already acquired a bunch of GAL chips that would eventually replace some of the "chipset" i'm going to have, but there's quite a bit of time to go until i get there.

My main inspiration is this amazing video series from John: https://www.youtube.com/watch?v=oekucjDcNbA&l … AEdgSQ4cz7HQZX5
He makes a CP/M compatible Z80 machine with memory bank switching and whatnot completely from scratch. Not only you will learn how to program Z80, but you will also learn how to design hardware, how to lay down a PCB and order them. The whole shebang!

What are your thoughts on all of this?

NB! Olimex also has Agon Light, that is z80 based. But in that one, the hardware is true hardware and the ESP32 on the board is just behaving as a second machine connected over serial line. So that is a lot less interesting, at least for me...