60

Using relays to implement logic functions was already quite well understood at that time, and in fact the Post Office type relays were designed to do just that as part of the telephone system. The fact that relays were also very reliable, could run on relatively low voltages, and were relatively power efficient were also marks in their favour. The major ...


18

Why were early 1940s computers predominantly made from relays? It was the technology proven to work reliably in large scale. A computer is large scale application, something a radio isn't. Building a new application is usually done by using a proven tools, not by inventing horse and carriage at the same time one wants to introduce a delivery service. "...


12

Switching Tech Tubes I do not recommend to use them because you would need to deal with high voltage and heat dissipation which can be potentially dangerous especially in class (pupils do not act with self preservation in mind sometimes). Relays Very nice alternative. Easy to understand (switch with electromagnet) using single low voltage (5V,12V,48V). ...


10

Wire Wrap as used in computers is simply a later development then the ENIAC or vacuum tubes in general (*1). The Keller tools were first marketed in 1953 and it took a few more years until they made their way from telephone to computers. IBM might have been the first, around 1960, a bit before the /360 came which, used it a all over. *1 - In contrast, PCBs ...


10

I'm going to suggest that this is very much asking to compare "apples to oranges". Vacuum tubes have MTBF values based on their design and operating conditions but they don't experience any "wear and tear" from normal operation such as switching. Relays, on the other hand, are electromechanical devices which experience mechanical wear ...


9

An couple of under-appreciated advantages of relays over tubes is that a single relay coil could operate multiple sets of contacts, and relay contacts could easily be wired into a variety of series and parallel arrangements that don't really work with tubes. Although relays that go beyond DPDT are today somewhat uncommon, and those that go beyond 4PDT are ...


9

Nice idea. I like it. Tubes et all. My general understanding is that in early computing, pre-solid state technology, a bit would represented by a single vacuum tube. That would be a missconception to start with. A tube doesn't store anything. In 'tube based' computers, tubes (usually triodes) provide a NOT functionality, as AND/OR are made up of resistors ...


9

My suggestion would be to use relays. Still readily available, and while you wouldn't be using vintage parts, there were definitely some computers built with relays. Can't handle as high speed as well as good vacuum tubes, but that isn't an issue here. The good part is that even if you can't see much - which will depend on the relay, you can hear every click....


6

But I'm used to a flip-flop being made of six transistors, which suggests it would need six triodes, Not really, a basic flip flop does not need 6 transistors. maybe there's a mix up with RAM cells? Two will do it quite fine (*1,*2). Similar the two triodes of a 6SN7 is all what's needed - well, plus two rather equal resistors between them and another two ...


6

I think that vacuum-tube-based computers were limited, besides storage speed etc., by the tubes' technology itself. There do exist hundreds-MHz tubes and even GHz range ones, but they are either have specialized design like this one: or they depend on the specific speed of slowly-moving electrons (like magnetrons, travelling wave or backward wave tubes). ...


5

Before caching, pipelining, and parallel processing (etc.) became commonly used to increase the performance of computer implementations, memory access speed was a bottleneck. Therefore, there was no need to try to implement any higher speed vacuum tube logic circuits required to support very high clock rates, as that would just waste power, thus reducing ...


5

How many logic gates did the IBM 650 have? It's a rather useless question. When is a gate a gate? Is a wired-OR a gate? Does a 38-input-OR, used to create a zero condition count as much as a two-input? Using a gate count does, if at all, only make sense for machines only build from diskrete gates. I'm used to measuring the complexity of a CPU by ...


4

I have found a high-level diagram of the structure of Colossus I. This cites an entry in the National Archives which has not yet been digitised but looks promising.


4

I'm personally intrigued by the use of neon lamps for storage, and although neon logic wasn't employed for anything particularly complicated back in the day, this could be a good application for it. A neon lamp will behave as a sort of switch that will not conduct until a certain voltage is applied, but once it does it will continue to conduct as long as a ...


4

This is a very interesting question. Apparently, at the time relays and tubes were used in computational equipment, there were no studies specifically regarding the lifetime of these components in such equipment. The state of the art was advancing at such a pace that relays and tubes were used for only a brief period of time and then left behind after ...


4

There is a case study in the form of the Harwell WITCH, which is a hybrid valve-relay based computer from roughly 1950. One of the design goals was explicitly to minimise the number of "hot cathode" valves in its design, as those were the chief source of reliability problems in the existing late-1940s experimental computers, and Harwell wanted a ...


3

Not sure I would trust 30 gauge wire wrap wire insulation with vacuum tube plate voltage. The cross-talk at the higher voltages plus digital edge speeds would also be far worse.


3

A large number of engineers had been building telephone switching networks for half a century, and phone company suppliers thus had lots of experience manufacturing good (telco quality) relays in vast numbers. Whereas vacuum tubes had never been used for digital logic circuits until Atanasoff–Berry, Tommy Flowers' team at Bletchley Park, and Eckert and ...


2

In 1963 or 1964 I saw a copy of the General Radio Experimenter magazine with an article discussing whether a 1 GHz computer was possible. It wasn't optimistic. It was pre-integrated circuits, so Grace Hopper's nanosecond wires (I used to have one) explained the problem, sort of. And while I'm on the subject, I read a science fiction story a few years before ...


2

The question asked why early 1940s computers were predominantly made from relays. The answer to this question might be simplified if limited to discussion of factual commercial and military activities in the United States from about 1940 to 1950. Relays were durable, and even as scrap many reclaimed relays worked ok. Tubes were more difficult to find. And ...


2

Here is a relay computer that was built in Japan in 1958 and is still going... https://www.youtube.com/watch?v=_j544ELauus I have wound relays. It is not hard. I have never made a valve. Early computing missed the plasma display. A neon lamp may take 20 volts to strike it, but will keep going with 5 volts. If you have a set of X wires at 0V and Y wires at ...


2

Relays had been around for a century. They are electrically controlled switches, naturally adapted to logical operations. There was a rich culture of using them as logical elements in telegraph, railway signaling, and telephone switching systems. On the other hand, use of tubes as logical switching elements was new and exotic. Rossi's coincidence circuit ...


2

You may be interested in this video about the restoration of a module with 8 vacuum tubes that looks very similar to the one in your video, but is a key debouncer. Details here and here. It's pretty unlikely that the module shown in your video is really "8 bits", unless the mainframe had internal registers that really used vacuum tubes instead of something ...


2

A conventional flip flop requires the following: Two inverting switching elements that will strongly pull their output in the direction opposite what's required to turn them on. Two elements that can weakly pull the output of whichever switching element isn't on in the opposite direction. Two elements that, in response to external stimuli, can pull those ...


1

Have done so long ago (RS F/F for a demonstration), without introducing brutal voltages, have lost the schematics :( What I remember is that I used an E88CC (6DJ8), with either 12V or 24V as an anode voltage and 6.3V as both heater and negative bias. Standard flip flop circuit. This was not capable of driving a standard LED directly (and low current LEDs ...


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