In March 1976, the Z80 8-bit microprocessor architected by Federico Faggin et al was launched by ZiLOG. Federico Faggin was the designer behind the worlds first commercial microprocessor, the Intel 4004, and later the Intel 8080, which was the foundation for the Z80 (backwards compatible with the Intel 8080). Despite the age, the Z80 is still going quite strong. Even today, products such as the recent TI-84 CE Plus graphing calculator uses the eZ80. But most people may remember Z80 from early 80’s home computers such as ZX81 and the ZX Spectrum.
For many years, I left behind my 80’s appreciation of the Z80. But, it was always in my heart and mind as the CPU, where I learnt so many skills about programming. Luckily, I have now discovered the world of retro-computing! And I was amazed to find out that some very high quality DIY kits are available at low cost to build a brand new Z80 computer today.
So it was time to “dust off” my Z80 skills, buy a soldering iron and get started.
If you have never built a computer before, I suggest starting with the SC114 by Stephen C. Cousins, it is quite easy to build even if you haven’t got much experience with soldering.
This is a great (and very cheap) starting point. What I love so much is the very simple design which allows full understanding of the circuits, even for a beginner with a minor level of understanding of digital microcomputers. The SC114 runs from a ROM containing a supersmart Z80 “Small Computer Monitor” program with assemble and disassemble capabilities. And a BASIC interpreter to do some “high-level” programming รก la 1978.
The SC114 can be expanded into a full CP/M 2.2 system using several options. I have chosen a solution from Karl Albert Brokstad in Norway. “The Missing Module” is an add-on board with a Compact Flash card interface, and a 115.200 baud high-speed serial port (the standard SC114 runs at 9600 baud). The Compact Flash card functions as a disk system, and allows booting into CP/M using the monitor.
Booting into CP/M:
Next Steps – Z180 and CP/M 3
For more advanced stuff, you can also build a Z180 based computer – a Z80 successor which is backwards code compatible, but also much faster and containing a lot of the peripherals that had to be added as extra ICs in a Z80 system. Again, several excellent DIY kit exists, below is an SC140 system with a Z50Bus. It runs CP/M 3, which is a great upgrade from version 2.2.
Read more about the SC140 system here.
