Finally, after a long time, the Program Counter and the 16-bit register unit are ready. I also received the cabinet from the smith.
After a whole month of work, soldering and debugging, the ALU is ready.
This week I finished assembling the 8-bit register unit. It has four 8-bit registers, A, B, C and D. Registers B and C are used as ALU input.
Here is the first finished part of the computer: the control panel. It is the user interface to the machine: from here it is possible to enter data to the RAM and registers, control and monitor the execution of programs and reset the CPU (empty all registers).
Why the heck would someone build a computer using obsolete technology when you got computers that are hundreds of millions times faster? Firstly because I always wanted to know how computers work. In the past, I have built simple adding machines, clocks and even tried to build a Z80 computer from scratch (which was a failure only because I got the schematics from 1979~1985 “Nuova Elettronica” magazines, and I couldn’t find many of the parts for sale, mostly because they were no longer fabricated). And secondly, for fun. Having such a monumental task in my hands, something to work for a lot of time and “keep my mind from wandering”. Also, having the experience of listening what a computer is thinking, is something really amazing.
In early 2012, I bought a very peculiar machine from a friend, who bought it from the junkyard. After looking inside, there were some seriously damaged circuits, so I thought it was not worth restoring it. The best decision was to tear the machine down to reuse the – extreme good quality – parts. I took several photos of the process, but I will only publish the best ones.