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On Z80 computers

2021-01-07 18:05 PST

Having just built my third RC2014 (and fourth Z80 computer), I figured I'd talk a little about my collection of Z80-based computers and what they're for.

This all started when I started watching Halt and Catch Fire. The biggest thing that I got from the show is a strange, overwhelming desire to design and build my own computer. I thought for sure it'd be a 6502-based computer, since I grew up on the Apple IIc. But I found the book "Build Your Own Z80 Computer" and that settled the matter. I started on the KZ80, but decided to build an RC2014 to have a working Z80 computer to test on.

RC2014 site

The first one I got was the RC2014 classic with a CP/M upgrade. I ran out of card slots, so I upgraded to the RC2014 Pro. I like this, but it takes up a lot of space. It's got an open bus so it was easy to do things like design and build my own SIO/2 serial card. But, the space issue and the loose cards aren't really working out for my current situation. I packed both of these up and put them in storage while I clean out my place.

I also found the SC131 pocket Z80 computer. This is small and has a case, so that's nice. And it runs RomWBW, which is my preferred CP/M distribution. But... it's hard to hack hardware on.

SC131

RomWBW

So I got the RC2014 mini with CP/M upgrade. It has headers for hacking on and doesn't have loose parts that make it fragile. It feels pretty solid.

The issue I have with all of these is that they operate over serial, which means that they need another computer to use them. While I'd like an FTDI serial console (like a modernised VT100), I don't have one. So the Kaypro is a standalone Z80 machine.

Once I get the software for the PCM4 working, I want to see if I can port it over the Z80 computers. 64K is a third of the memory of the PCM4, and 2.5-8 MHz on an 8-bit is a step down in computing power, but still would be cool. Especially if I get the KZ80 working... my own OS on my own hardware, the perennial dream.