I was so impressed with the Zeta 2 design when I built my floppy controller for the RC2014 that I decided to go ahead and build a Zeta V2 as well!
As you’re probably aware if you’ve read my previous blog posts, one of my recent hobbies has been retrocomputing, building computers based on the techniques of the 1970s and 1980s. Most of the projects I’ve built have been based on the RC2014, but I came across the Zeta 2 and decided to give it a go as well. The Zeta 2 is designed by Sergey Kiselev. There are PC-Boards available at the Vintage Computer Forum for $20 each.
The Zeta 2 differs from the RC2014 in that the Zeta 2 pretty much gives you everything you’re going to need (CPU, Parallel IO, Serial IO, Storage, Ram, ROM, clock, etc) all in a single PC-Board. As such, it’s relatively easy to assemble a fully-functional CP/M computer and has a working CP/M distribution that runs right out of Flash ROM. If you want to get a fully functional CP/M computer up and running quickly, the Zeta 2 is a great way to go.
Here are a couple pictures of my Zeta 2 Build:
A few of the features of the Zeta 2:
Most of the ICs are easily sourced from places like Digikey or Jameco. A few of the more unusual ones, like the WD37C65 floppy controller, you may have to find at a site like eBay. Make sure to plan out your part acquisition accordingly (if you order some chips from eBay, note that suppliers are often in China and it may take a few weeks for parts to arrive).
As you can see in the bottom view of the board, I used a stacking header. This allows the parallel port to be connected from either the top or the bottom. The reason for this is that there’s a companion board designed to work with the Zeta 2 called the ParPortProp:
The ParPortProp uses up the A and C ports of the Zeta 2’s 8255 PIO chip (leaving only 8 bits of PIO remaining), but provides you with:
The ParPortProp uses the Parallax Propeller micocontroller, a relative modern chip, so it diverges a bit from what we might consider classic retrocomputing. The Zeta 2 is still your “computer”, but the ParPortProp is acting as a terminal attached to the computer. This lets you connect a keyboard and monitor up to your Zeta 2, giving you a standalone computer than you can directly interact with.
The biggest disadvantage of the ParPortProp is the amount of PIO that it consumes. If you’re like me, and you like interfacing lots of things to your projects, then you might find the remaining 8-bits of PIO somewhat unsatisfying. The ParPortProp is completely optional though.
I really enjoyed building this kit. I was able to get CP/M up and running almost trivially. CP/M runs out of ROM so even if you don’t have a storage subsystem handy (floppies, SD Card, etc), you still have a fully functional computer.