Somehow, it feels like yesterday, but nearly three decades have already passed since home computers like the Sinclair ZX Spectrum found their way into our living rooms. My first contact with a computer was in the early 80’s, after my father had bought one of them.
I was five or six years old at that time. The specifications of the device look poor compared to contemporary PC’s, but it’s astonishing what you could do with a 3.5 MHz machine with 16 kBytes of ROM and 48 kBytes of RAM. (The RAM included about 7 kBytes of video memory, not available to applications.) With my father and brother, I spent many hours with such games as “Jet Pac” and “Pssst!”. Games came on standard cassette tapes and took a couple of minutes to load. The loading process was accompanied by a futuristic sound which contained the encoded 0’s and 1’s of the program code. There was no monitor - instead, we used the PAL TV screen to display the image from the Spectrum.
One of my first computer programs was called "Ski lift". It was written in Basic with the Spectrum’s integrated Basic interpreter. You had to navigate the skier, represented by an uppercase ‘M’, down a hill with trees, represented by characters '^'. Every level had more trees, and a crash of the ‘M’ with a tree ended the game. This was nothing compared to the “professional” games like "Jet Pac" and "Pssst!"", but somehow, it fascinated me in a way which finally led me to my today’s job as a software engineer.
Recently, together with some friends in the observatory, I travelled back into the past when we discovered a web page with a ZX Spectrum emulator. It runs a lot of the old games, and starting in 2009, people have even started to develop new games for the machine.
On the way home, I decided to build my own ZX Spectrum 48. The Mitsubishi TFT display would replace the TV screen, and I also remembered that I had some Z80 CPU’s in my box of spare parts. The ROM should fit in a 27128 EPROM. To connect the computer to the TFT display, I would use the Spartan-III starter kit.
Back home, I googled for some schematic diagrams and information about the "inner workings" of the ZX Spectrum 48 and finally ordered one of the best books I’ve read in the recent past, "The ZX Spectrum ULA Book". In the next night, the project started to take shape in my head...