61 votes

Why were relays prevalent in early 1940s computers when vacuum tubes were also available?

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 ...
Chromatix's user avatar
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18 votes

Why were relays prevalent in early 1940s computers when vacuum tubes were also available?

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 ...
Raffzahn's user avatar
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12 votes
Accepted

Smallest/Simplest, modern pure relay computer with at least 4-bits data words

How about a Turing machine implemented with relays? If I didn't miscount, there are 8 relays plus 1 relay for each bit of the state (for a total of 12 with 4-bit state). Let's see your conditions: ...
dirkt's user avatar
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10 votes

Have there been any studies comparing the reliability of relay versus vacuum tube computers?

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 ...
jwh20's user avatar
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9 votes

Why were relays prevalent in early 1940s computers when vacuum tubes were also available?

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 ...
supercat's user avatar
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8 votes
Accepted

Did any computers use automatically-operated mechanical storage as electronically-read-addressable memory

Removable plugboards were a common form of read-only memory which I think fits the criteria. ENIAC plugboards were not removable, but later computers used low cost removable ones. They were adapted ...
mgkrebbs's user avatar
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8 votes

What is the first (say early) use of switches (mechanical or electromechanical) for sake of processing (like automatic motor control)simple data?

The first recorded use of relays in process control computing is in a patent granted to John Saxby in 1856. A brief description is given here. They were used to control railway signalling. The '...
Chenmunka's user avatar
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8 votes
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What is the first (say early) use of switches (mechanical or electromechanical) for sake of processing (like automatic motor control)simple data?

Switches are intended for just turning ON or OFF the power supply by either closing or opening the circuit. Not really. Switches in process control are intended to sense a state. That the result and ...
Raffzahn's user avatar
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8 votes

Smallest/Simplest, modern pure relay computer with at least 4-bits data words

I just found this discussion and I wanted to correct a few mistakes by Jules about one of my projects, the YGREC8 (I'm the YG of YGREC). There are many relay-based projects, look at https://hackaday....
YGREC8's user avatar
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8 votes

Relay computer performance

Well, a good datapoint here may be the Zuse Z3 and Z4 computers. Not at least as their workings are close related to today's computers in being tact controlled as well as using binary floating point ...
Raffzahn's user avatar
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7 votes

How did relay computers handle inductor flyback?

From electronics point of view, the simplest part that can be used for this purpose is a resistor across the relay coil. The inductive voltage spike will then have a maximum voltage of I · R, where I ...
jpa's user avatar
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7 votes

Smallest/Simplest, modern pure relay computer with at least 4-bits data words

Neither of these are quite what you're looking for, but I'm including them because I think they're worth looking at nonetheless, and I think both are more interesting than the designs you've linked ...
Jules's user avatar
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6 votes
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Floating Point on Konrad Zuse's computers

Konrad Zuse's computers all did floating point in hardware. I am interested in implementation details here. The very best way here would be Raul Rojas books. Most important: Die Rechenmaschinen von ...
Raffzahn's user avatar
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6 votes

What was the specific function of the relay which captured Grace Hopper's famous "bug"?

Parts of this answer are necessarily speculation, especially since the way the machine worked (and its bizarre programming model) are buried deep in time, or at least deep in various museums(1) :-) ...
paxdiablo's user avatar
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5 votes
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Have there been any studies comparing the reliability of relay versus vacuum tube computers?

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 ...
Chromatix's user avatar
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5 votes

What is the first (say early) use of switches (mechanical or electromechanical) for sake of processing (like automatic motor control)simple data?

Mechanical switches were put to good use by Jacquard in his loom in 1804. This was a refinement of automated controls originating in the early 1700s, and his ideas were later adopted by Charles ...
Stephen M. Webb's user avatar
4 votes

Have there been any studies comparing the reliability of relay versus vacuum tube computers?

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 ...
Thomas Perry's user avatar
4 votes

What is the first (say early) use of switches (mechanical or electromechanical) for sake of processing (like automatic motor control)simple data?

Maybe not the earliest, but early and important, and very elaborate uses: Automatic telephone exchanges. Strowger, 1891. Elevator control (early 20th century). Telegraphy, especially teleprinters (...
rackandboneman's user avatar
3 votes

Floating Point on Konrad Zuse's computers

there are more solutions to speed up the bit shifts in general: align shifts to data word Simply use your platform WORD bit width and align your shifts to it... That means if I have an 8-bit data ...
Spektre's user avatar
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3 votes

Did any computers use automatically-operated mechanical storage as electronically-read-addressable memory

There are a number of possibilities, though most of them involve stretching the definition of "computer" somewhat: The Zuse Z1, Z2, and Z4 computers used slotted metal strips as memory. Of these, ...
Mark's user avatar
  • 8,547
3 votes

Why were relays prevalent in early 1940s computers when vacuum tubes were also available?

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 ...
hotpaw2's user avatar
  • 8,183
2 votes

Why were relays prevalent in early 1940s computers when vacuum tubes were also available?

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 ...
Thomas Perry's user avatar
2 votes

Why were relays prevalent in early 1940s computers when vacuum tubes were also available?

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 ...
Richard Kirk's user avatar
2 votes

Why were relays prevalent in early 1940s computers when vacuum tubes were also available?

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, ...
John Doty's user avatar
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2 votes

Did any computers use automatically-operated mechanical storage as electronically-read-addressable memory

I think core memory is what you are looking for. You may not think of it as a mechanical solution however it was. Core memory is electrically set and read, the read is destructive so part of the read ...
Rowan Hawkins's user avatar
1 vote

Smallest/Simplest, modern pure relay computer with at least 4-bits data words

I am sorry if this message goes here (it doesn't answer your question directly) but I am totally new here and I might have misconfigured something. I have now registered this (apparently different) ...
YGREC8's user avatar
  • 21
1 vote

Did any computers use automatically-operated mechanical storage as electronically-read-addressable memory

The Zeus Z1, Zeus Z2, and Zeus Z4 used "mechanical slotted metal strip memory". These were not stored program computers where the program is executed entirely out of main memory; rather, ...
Wayne Conrad's user avatar
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1 vote

Did any computers use automatically-operated mechanical storage as electronically-read-addressable memory

This is an edited and expanded copy of an answer I posted elsewhere; it was pointed out to me that it would be useful information here. EDSAC (operational in 1949) had read-only memory to hold its ...
dave's user avatar
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