The cover of the October 1950 issue of Radio-Electronics magazine featured a picture of a desktop-sized relay-based "electric brain" called Simon. The issue contained the first of a series of 13 articles presented over the next year about the principles of digital automated computing. Edmund Berkeley, the principle author of the articles, had also just written a book "Giant Brains and Machines that Think" (Wiley & Sons, 1949).
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Simon was likely the first attempt at producing a minimal or affordable automatic digital computer for educational purposes. Several large computer construction projects had been completed or were underway at the time but only the cognoscenti had access to them. Simon would introduce the principles of binary arithmetic, logic and automatic computation to a wider public.
|Brief Technical Overview|
Simon is a Harvard architecture machine constructed from relays. The program is executed directly from paper tape. In these regards it was behind the state-of-the-art as several electronic stored-program machines were under design or construction by the late 1940s. The main data registers and ALU are 2 bits wide, data input is via either the paper tape or 5 toggle switches, output is via 5 lamps.
As an educational instrument, Simon was directed more towards the electrical implementation of logic than towards programming. As such, and as a minimal machine, programmibility is rather limited. The one saving grace may be that the program can be quite long (limited only by paper tape handling), a feature that certainly would not have been feasible in an attempt to make an inexpensive stored-program machine at the time.
The name "Simon" came from the Mother Goose rhyme "Simple Simon", the designers freely referring to the machine as "the little moron".
|Simon and the Radio-Electronics Articles|
The 13 Radio-Electronics articles are broadly broken into two sets, the first 7 articles covering "electric brains" and the final 6 covering "electronic brains". The final 6 articles are not relevant to Simon.
Even within the first 7 articles, much of what is presented is not applicable to Simon. Most of articles III and IV are devoted to binary multiplication and division with relays, operations which it later turns out are not implemented in Simon.
Inconsistencies, ambiguous references and missing details can leave one perplexed as to Simon's design and capabilities. Some diagrams in the articles show registers and data paths 4-bits wide, while the text states that they are 2-bits wide in Simon. Large portions of the circuitry are never shown in detail. There is no overall functional or block diagram of the machine and no complete schematic. Even the instruction encoding is not fully described.
Fortunately, the timing of the machine cycle of Simon is covered in some detail in the articles, being very helpful to deducing aspects of the machine.
I initially ran across the Simon articles a few years ago when I was sorting through some boxes of early R-E magazines. While they certainly caught my attention I confess I was disappointed. The authors do admit to the incompleteness of the Simon description but such mention is left for the final paragraphs of the 7th article.
After studying the articles more closely however, teasing out as many details of Simon as possible, and going through the exercise of creating the machine definition, the ingenuity of the design becomes apparent.
For amusement, I just have to mention the tortured attempt by the authors to bring Cold War politics and patriotism into a technical article. Witness this extract from the first article (note: the reference to a telegraph system is from an analogy being made between a computing system and a telegraph system earlier in the article):
As a programmer of Simon one could feel much more as though one were working under the formerly mentioned system than the latter.
(Another digression: If one happens to have the magazine issue containing the first article, take note on page 33 of the photo of Jay Forrester with a holding-beam storage tube for Whirlwind.)
|References, External Links|
| Relay Implementation