Recently, I’ve bought a 1984 vintage Z80 board on eBay. The board is a piece of the ancient 8 bit homebrew computer area when computer enthusiasts often had more skills in soldering techniques than they had in software engineering.
The board is a bare Z80 with a clock source, reset circuit and some bus buffers. In fact is it a part of German TV history: In 1984 German station ‘NDR’ started an educational series on the principles of computing. Other than the well-known BBC series “The Computer Programme”, people who liked to participate had to buy an extensible kit and assemble them. The result was a modular system called the “NDR Klein Computer”.
To test the board, I used an old eeprom that once gave home to a 486 Award PC BIOS. After adding a 32K Windbond cache ram chip from the same old PC and some latches that form a simple I/O interface to the bus, I now have a running system that I can run my firmware with.
Next will be a Z80SIO chip to connect a terminal to the machine and a floppy and hard disk emulation with an Atmel µController and an SD card.
It’s really amazing, how much fun it is to build a small system that could have been a ‘decent’ system back in the days when the first PCs where coming to the market.
µControllers are different
Sure, an Arduino has all out of the box: Clocks, RAM, ROM, C compilers, I/O ports including ADCs, timers, interrupts, etc.pp.. But it’s so much cooler to actually build the hardware with a handfull of TTL chips and a solder iron. And how gorgious would a DIY 8bit machine running CP/M with a CRT attached to it be?