EDDA 3 - An Early Transistorized Process Computer

(This article is also available in a German version, thanks to Mark Gerber for translating it to English).

In the midst of the 1960s the process computer "EDDA 3" was developed by Carl-Schenck-AG in Darmstadt, Germany. The field of operations was the industrial weighing and dosing technology and the computer’s design engineer was Rudolf Meyer. The author of this essay is a friend of Mr. Meyer’s son, and already during the age of 15 both were granted to unsolder precious transistors from used EDDA boards. In February of 2010 contact arose again, and Mr. Meyer kindly provided valuable original documents and personal memories. He passed away in April 2020 in age of 88.

EDDA3-Label  Schenck logo

The following article pages are gathered from the EDDA 3 user manual with 160 pages. These few pages contain everything you need to build and run an EDDA computer: Theory of digital process control, digital number representation, data transport inside the processor, implementation of an adder, complete architecure of the processor, processor operation in each clock time slice, instruction opcodes, data address space, i/o registers, programming examples, instructions how to connect different types of i/o devices, principals of an hierarchical i/o expansion module system, function of different i/o modules, debugging features, electrical checkout procedures, programm debugging procedures, and technical parameters for every module.

Document language is generally German. Behind all original scans I've given translation to English.

These are the title pages of the user's manual:

 manual klein 

Systembeschreibung zum digitalen Prozeßrechner EDDA 3

Dipl. Ing. Rudolf Meyer

Carl Schenck Maschinenfabrik GmbH - 61 Darmstadt
Darmstadt, im Nov. 1969


1. Einleitung
2. Der Prozeßrechner EDDA 3
3. Elemente der programmgesteuerten digitalen
4. Aufbau und Arbeitsweise der EDDA 3
5. Die Programmierung der EDDA 3
6. Anschluß äußerer Schaltungen an die Eingabe-
   und Ausgabekanäle
7. Erweiterung der Kapazität der EDDA 3
8. Prüfung der EDDA 3
9. Technische Angaben


Translated this reads:

System description for the digital process computer EDDA 3

Table Of Contents:

1. Introduction
2. The process computer EDDA 3
3. Elements of program controlled digital data processing
4. Construction and principals of operation of EDDA 3
5. Programming the EDDA 3
6. Connecting external peripheral circuits to input and output channels
7. Enhancing the capacity of EDDA 3
8. Checking EDDA 3
9. Technical properties


Title Author
EDDA 3 - Introduction Written by Administrator
EDDA 3 - Processor Architecture Written by Administrator
EDDA 3 - Program Memory Written by Administrator
EDDA 3 - Data Address Space Written by Administrator
EDDA 3 - Peripherals Written by Administrator
EDDA 3 - Sample program application Written by Administrator
EDDA 3 - Operational Safety Written by Administrator
EDDA 3 - Personal Memories and Actual Operation Written by Administrator
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