Commander X16

I've grown up in East Germany and at the end of the 80s I've managed to assemble a computer described in a magazine. A few years ago I've learned that the processor was an east german copy of the Zilog Z8. You needed to find the parts (some chips weren't easy to get at this time), draw and etch the circuit board and find one who can program the EPROM. While being electronics addicted since the 4th class, this made me become software addicted. The magazine not only described the hardware and some extensions, but also printed some smaller BASIC programs as well as the processor's details including the assembler language. I used this 8-bit machine to create my own operating system (later I was able to flash EPROMs myself using this machine), to create own games. Some of the games I've got from a pal who developed them own completely different hardware (with different processor and graphics) and provided me the assembler code.

Later I've received an obsolete Commodore machine with floppy drives and in the last weeks I've recognized it could have been a PET.

5 years after I had enough money to get the hand on a used 286 PC and that was the end of my 8-bit career. I've sold my self-built machine for ~100 DM which I regretted later. When Arduino became popular >10 years ago I immediately liked it, but it wasn't the same. It was not much more than a bare processor without much hardware around it, most noticable it was not usable as an 8-bit computer to develop and run arbitrary software on it that was not on the flash already. But it also showed what a 8-bit dream-computer should have for me: it should be easy to program from a stock PC.

BTW, if someone is interested in this Z8 computer, there are some pdf files available (I don't know whether I'm allowed to link them directly): https://duckduckgo.com/?q=ju%2Bte+computer+hoyer+selbst+gebaut&t=ffab&ia=web (there is also an emulator available at http://www.jens-mueller.org/jtcemu/). Of course, this is written in German, but the schematics should be readable by non-Germans, too. I mention this, because it did not need a special graphic chip but used a second Z8 for the 320x192x4 pixel graphics that shared some memory with the main Z8. In my machine I also made memory switchable banks by soldering RAM (62256?) on top of each other, except of their /CS pins.

Hello! This all is quite impressive! There were similar build your computer articles in 80's magazines in my childhood as well. But it is always interesting to learn about more of them.

Possibly the most successful was the Australian Microbee, which was published in a magazine and ended up being the Australian school's machine, as did the Galaksija in the former Yugoslavia.

Some of them were excellent, but they had the same problem retrocomputer projects do now, a big enough user base to produce software. Which is not a problem if you just want to tinker, of course. I think the first three computers I had I had one commercial game ...

this is amazing, I can see the jute, and can see that it doesn't work anymore, but wow, what amazing keyboard and it had sound too! basic stuff. I am so intrigued by everything from the USSR, like Buran is so amazing and everything looks so different in engineering, it's a wonderland. I had not even come across the Z8 before, you learn something everyday, and I see where you double the ram using just the CS pin, I see where it comes from now, like an antonov and Buran, the CPU and the rom. I hadn't ever seen it done outside of hobbyist world before. Amazing.

 

Small correction: the Z8 clone was made in East Germany, not the USSR.

What I really like about the Ju+Te computer in the 320x192 pixel variant is the brilliant idea to use a second processor with nop and jump commands to create the timing for the monitor signal and the addresses for reading the video RAM.

yes, I've considered that myself in regard to the Z80, which has a refresh counter which could be utilized for many things. I think that the 4040, 4020 and 4060 timer ICs generally beat out the Z80 for stability and ease of understanding and so on, because for the pixel clock, the CPU is overqualified for the job. It is for certain a great innovation to make from construction point of view, because you are sure to have them there on the bench already and don't have to go find them or wait for a solution to arrive in the mail.

However, the Z80 NOPs are a winner on the project I am working on, where you write the BIOS bootloader yourself, into blank memory chips using the keyboard. The Z80 wins because it can clock at DC to Mhz, which means it can wait for the slowest typist in the world to do the next characters. Now the Z80 wins on economy and simplicity because it is already requisite to the design, plus it is already wired up to the memory chip in the way it needs to be wired up to the memory chip for both writing BIOS AND running the machine. Total win.

Sorry about the confusion I cause about the USSR, I mean to say the 'other side' of the iron curtain, where the technology is like relentless, formidable, uncompromising ... If I were a king and great Britain was attacking I'd try to hold a straight face, if it were Russia, I'd say my prayers.They own orbit. They live there. For most people's whole life.

In case someone is interested, the community around the JU+TE computer (aka Tiny computer) is still alive:

https://www.robotrontechnik.de/html/forum/thwb/showtopic.php?threadid=16542

https://www.tiny-computer.de/

Fascinating! This is the first time I encountered the Z8 in something like practice ? - I knew about its existence for a long time but never saw it used, as far as I can remember.

Amazing collection of material also at https://hc-ddr.hucki.net/wiki/doku.php/tiny.

@Ju+Te, did you also use the FORTH system that is described there?

I've tested Forth >30 years ago on this machine, but I remember it being relatively slow - compared to normal assembly programming.

At the moment I'm in the process of rebuilding this Z8 based machine.