The Junior computer design was published by Elektuur/Elektor from 1980 on. It was published in a series of magazine articles, four books and several socalled paperware A4 booklets. Loys Nachtmann designed and developed the the Junior Computer. G.H. Nachbar did the Dutch translation of the German books. The 4 Junior books were translated into English and French as well.
The Junior design is in fact inspired by the hardware of the KIM-1, the floppy design iss based on the Ohio Scientific OS65D design. It was delivered as a kit or could be be built from only the PCB's sold by Elektuur. Many hobbyist have built one. Later extended with an adapted version of the 8K KB9 Basic and even a disk operating system (Ohio Scientific DOS OS65D).
Many articles in the Elektuur magazine and books (1-4), a 6522 book in the same series, in Dutch, English, French and German have been published.
Quickly adopted by the dutch KIM Gebruikers Club because it was so close to the KIM-1. In the later days the number of Junior Computer users exceeded the KIM-1 users and changed the nature of the club from professional users to a hobby club. It also led to the DOS65 operating system for the Elektuur 6502 CPU board
The magazine Elektuur (the dutch name) and Elektor (the name in many european countries) surprised us in 1980 with the publication of a build-yourself 6502-based SBC. It is a design in the tradition of the KIM-1 and SYM-1: a hexadecimal keyboard, six hexadecimal led displays and KIM-1 compatible tape format.
Many Junior Computers were built, either from the PCB made by Elektuur and separate components or as a complete kit. And after we (Anton Muller and me) sent a letter to the Elektuur magazine that got published about the KIM Gebruikers Club, many hundreds Junior users joined the club.
The developments after the Junior design in Elektuur led to the EC65 and DOS65, but that is another story to be documented.
Ruud Baltissen has developed PCB designs of some of the more interesting Elektuur designs like RAM, cpu and other cards.
Also have a look at the page devoted to Elektuur/Elektor and the 6502 where yopu will find all Elektuur articles and books on Junior, Octopus and micropsrocessor related articles.
The Junior as built by Marc Engrie.
2708 ROM image dumped and disassembled by Ruud Baltissen
PM ROM image dumped by Rob van Oostenbrugge
Junior ROM in 2732 format made by Rob van Oostenbrugge
This ROM dump only contains the monitor parts, not the editor nor assembler.
A 2732 EPROM can be used instead of the 2708 EPROM when:you perform the following:
- cut the traces +12 and -5V
- K6 to the VIA,
- k7 to the EPROM.but leave k7 to the 7401 intact for the STEP function.
- /cs from VIA to K3. to move the VIA to page 0E (jumps in the eprom are adapted for that)
- /OE from the2732 to ground
- A10 and A11 of the 2732 to the adresbus
- /cs from the 2732 via an inverter to A12 , note that there are two unused ports in the 7402 with grounded inputs,: cut those! and add a pullup resistor.
The Junior was sold as a kit by the firm Musicprint, read here the extra instructions in the kit.
In a package with Elektor hardware Octopus cards I recently bought, I found a little book and a floppy with Junior tape dumps. In binary format! Made with what I think is an 68000/Atari/Amiga program. it is also included. The files could be restored back to tape with the Ed's DX-Forth and Utilities.
Included are sources and programs like
- Junior PM and TM
- memory test
- Micro Ade, KIM-1 and Junior version, also in source format and extended format
- Clock source program
- CW Moser assembler/editor, also in source
- Forth, Comal
- SYM Basic adapted to Junior
See the included juniortapes.txt for a complete listing of First book of KIM programs adapted to Junior
Musicprint cassette interface
It took Elektuur some time and the potential user a lot of money to add a cassette interface tot the Junior design, Many users therefore bought the scalled musicprint cassette interface. See here the description and circuit design.