Week 105: Eight bits
I soldered together a computer. It uses a Z180 CPU, which is a compatible successor to the Zilog Z80 that requires slightly less external plumbing. It follows the RC2014 modular architecture and I used kits from Small Computer Central and Z80kits to make it, specifically, the SC203 system, Compact Flash module, and Real Time Clock module.
There was quite a lot of soldering – at least 400 points for the bus connections alone – but it took me about half a day in all. I have a computer with CPU, ROM and RAM, a real-time clock with battery backup, and hard disk emulation using a 256 MB Compact Flash card I had in a drawer.
It runs a variety of 8-bit Z80 software, but the thing I’m most interested in playing with is CP/M (and the improved compatible Z-System). CP/M was the first proper operating system I used, on the Amstrad PCW computers at school. One of the teachers had a library of 3 inch floppy disks with all kinds of odd programs and games, all running in a text-based interface.
There is something slightly ridiculous about the fact that I have to connect a vastly more powerful computer via a serial port to use it, and I could of course just run an emulator instead, but something about tangible things is more fun, somehow.
I spent a bit of time tidying up and documenting my Axoloti control board. It’s not tremendously useful to many people, because the Axoloti board itself is unobtainable due to the chip shortage. Someone in Denmark saw a photo I’d posted and got in touch to ask about the circuit board designs, so I sent him a spare board and tidied up the repository so he’d know how to use it.
I still have three PCBs left, so if you’d like one, get in touch!
I had an enjoyable couple of days doing a bit of data analysis for work, using Jupyter and pandas to query a MySQL database and wrangle it into a presentable format. I wrote about that earlier. It’s fun to do something a bit different from writing software once in a while. As my grandmother, who spoke almost entirely in aphorisms, always said, a change is as good as a rest. She also said that worse things happen at sea, though, so maybe that’s only true of dry-land-based changes.
The Christmas tree is gone, put out for the council collection one day shy of Twelfth Night. We still have a box and a half of mince pies left, however.