Retro computing

My first computer was a ZX81 which I got as a birthday present in 1981. Since then computers became basically an obsession and the venerable Z80 processor is still one of my favorite CPUs. Clicking on the picture brings you to a page describing the development of a rather simple Z80 based computer with serial line interface, and an IDE controller.

Of course, any computer without at least a tiny operating system is not too useful in the long run. Thus, I wrote a monitor for this (and other) Z80 based systems from 2011 to 2017. I borrowed heavily from other sources, such as Camel Forth, a good Z80 disassembler, even Microsoft Basic. Clicking on the picture will bring you to the github project.

Clicking on the picture on the left will bring you to a page which describes a simple AVR processor based video controller for the small Z80 system.

In 2013 I made a really tiny Z80 based computer which was copied by quite some of my students who really liked the opportunity of building a small computer and actually being able to understand it in detail. Clicking on the picture opens the page describing this little project.

In October 2013 I got a box containing a number of classic processor chips as a present from a friend. Among these ICs were some made by Texas Instruments, including the TMS9995, a scaled down version of the TMS 9900 of which I am especially fond. Clicking on the picture brings you to a page describing a simple homebrew system based on the TMS 9995.

One of the most fascinating early microprocessors is (at least from my point of view) the TMS9900. Unfortunately, there is not much software support nowadays. Thus, I wrote a simple, yet powerful assembler for the TMS9900 in Perl which should run on basically any platform supporting a Perl interpreter. Click on the image to get to the corresponding github page.

Many years ago a friend of mine donated a box of TI 9900 related boards - enough to build an actual TMS9900 based system. However, this turned out to be quite tricky since one of the address decoding PROMs was defective and I had to reverse engineer its contents and build a suitable replacement. Click on the picture to read the full story of this build/repair/restoration project.