Elektor Junior pages updated

After several years so much new and correct information has been coming in!

While I was studying the Comal interpreter, I want to port it to the KIM-1, I realised the Elektor pages required some updating and reorganising.
I could not find easy what I needed: circuits and source listings. So I extracted the circuits from the articles and checked the various listings with the ROMs I had in my archive.
Also the sources that appeared the last years were checked, adapted and the binaries compared with the hex dumps. Some surprises, many faults and not with the correct names.
The ESS numbers are now attached to the ROMs.

Now you can have all the essential Elektor Junior information from base to full system with checked ROMs, with sources, step by step.

The complete archive of articles and books is also updated, especially the English articles are as complete as possible.

Have a look at the Elektor Junior pages!

With thanks to the many persons and fora that helped me to collect the information.


Elektor Universal Terminal

Published in 1983.

A VT52 terminal build up with the VDU card, known from the Junior articles, and a new CPU card, later the base of the Octopus/EC65 computers.

VDU card
ESS522 character generator ROM
CPU card
CPU card and Universal Terminal
(to be burned at location $F9DF to let the 6502 vectors appear at upper memory)
Paperware 3, listing of ESS525 ROM in Micro ADE format
Universal terminal source in MICRO ADE format
Universal terminal sources and hex files



Elektor published in 1978 the Elekterminal design: a video display unit and an ASCII keyboard for computer systems with serial interface.

Over the years the design evolved and many articles were published. Among other systems, it was also integrated with the Junior computer.
The Juinor book 3 contains a detailed description how to combine Elekterminal and Junior via the bit banged serial TTY interface.

The video display was later replaced with a videocard, the serial ASCI keyboard stayed as option.

Articles and books in English about the Elekterminal

Elekterminal articles 1978-1980
Junior book 3
the Elekterminal with a printer
lowercase and special characters on the elekterminal
Elekterminal bell
Elekterminal character generator with lowercase, 2716 EPROM image


Junior KB9 Basic

Junior KB9 Basic

Philippe Roehr started with the KB9 binary from the KIM-1 pages.
Philippe then applied the process outlined in the Elektor articles to adjust Basic to the Junior character I/O routines and also improved the speed by adjusting the now unnecessary code that took care of the ROR bug in early 6502’s.

Philippe transferred the binary to the Junior with Ed’s utility KIMTape, producing a KIM-1 audio wave file. The Junior accepts this format, a bit slow but only needed once. After seeing all was well, Philippe wrote the now optimized Junior KB9 Basic to audio wave file, and made a hex dump on the terminal. I picked up the dump, a captured text file form a a terminal emulator, and wrote a conversion program to produce a binary.

All the files here: archive with audio wave file, dump on terminal, binary and conversion software.




Based upon information supplied by Philippe Roehr, see also the DIY Build a Junior page

After building the Junior, having PM and TM monitor working well, KB9 Basic operational, the next step Philippe took was getting the operating OS65Dv3.3 operational.
He took the steps described by Elektor in the articles with some modern additions.

A Junior able to run OS65DV3.3 needs an expansion card, a RAM card (his is 64K) and the Elektor floppy controller, which is identical to the OSI one (6850 + 6820 ICs)

Instead of a real floppy drive Philip used the hardware Gotek floppy emulator with the Flashfloppy firmware. And used the manuals images of http://osiweb.org, and the OSIHFE utility described in the OSI Web forum posts.

Elektor made a bootstrap eprom (see the floppy disk page) able to
* load OS65D (V3.1 or 3.3 as far as I know) from floppy
* give basic I/O capability (RS232 and floppy)
* manage hex display and keyboard
* modify OS65 for the hex display after the very first load to fully adapt them to the system ( about 10 bytes to modify)

Here the OS65DV3.3 disk image in native and Flashfloppy format ready to use.

During the second part of december 2020 Philippe added a real floppy controller and added the Ascii Video Terminal (new version of hackaday). With improved moter control of the floppy drive!

Junior DOS

The floppy disk system for the Junior was based upon OS-65 V3D from Ohio Scientific, the interface is a clone and, since the software was for sale, a separate object.

VDU board with OS65D

PMV for OS65D source checked by Philippe Roehr

Floppy disk interface

Circuit of the floppy disk interface. Not the usual circuit based upon a well-known FDC controller IC, but a simple and not so standard solution. The OS65D operating system from OSI, Ohio Scientific, knows how to handle this interface well, and just for this purpose, Elektor choose this solution.

floppy disk interface for the Junior part 1
floppy disk interface for the Junior part 2
Sources and hex files of PMV, PM for VDU and OS65D
Paperware 2V listing of bootstrap ROM ESS515
Sources of ESS515 ROM
ESS515 bootstrap ROM
Paperware 3V PMV listing, adapt PM to VDU and OS65D

The next page gives information on OS65D, the operating system.

VDU Videocard

An Elektor bus based videocard around the 6845 videocontroller. Composite video, two colours: black and white.

VDU card
Paperware 2V listing of bootstrap ROM ESS515
Paperware 3V PMV listing, adapt PM to VDU and OS65D
ESS522 character generator ROM
Viditel character generator ROM
Sources of ESS522, the character generator ROM
Sources and hex files of PMV, PM for VDU and OS65D
Hex files of PMVV and TMV and character generator for VDU

16/64K dynamic RAM card

In a time when SRAM was expensive, power hungry and small it made sense to use dynamic RAM: larger, cheaper.
First in 16K format, later in 64K format.

dynamic RAM card
64K on the 16K dynamic RAM card

Have a look at the Elektor Articles and Books page for a mullti-lingual overview of all publications on Elektor/Elektuur Junior and more.


Italian Junior articles

Italian articles 1980-1985


Replace the 2708 EPROM

The 2708 is not an easy EPROM to use. It requires -5V, +5V and +12V and most programmers can not handle it.

Elektor published an article how to use a 2716 instead of a 2708 (eliminating also the need for -5V and easier programming).

ROM in 2732

But an even more common 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 the 2732 to ground
– A10 and A11 of the 2732 to the addressbus
– /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 pull up resistor.