Colossus gets cracking again

  TopCat® 19:15 15 Nov 2007

after its fourteen year rebuild and is pitted against a modern computer - specification not disclosed - in solving German wartime codes. I hope its thermionic valves will warm up to the job and last to see it completed! click here

There's an interesting timeline link too from Michael Faraday right up to the silicon of modern times. TC. click here

  Totally-braindead 19:17 15 Nov 2007

That would be a great thing to have in your house in the cold weather, presumming you had the space as it would heat the house for free.

  octal 19:37 15 Nov 2007

My wife says it looks like my radio shack :D

I've been following the history of that machine it's quite interesting.

Apparently they don't really know how fast it can process numbers, because at one point they tried running the tape through at 60MPH and although the machine was still processing the tape was at risk of catching fire! I'm not surprised, because all the valves are on a parallel bus.

This is Tony Sale's site. click here

  Earthsea 19:46 15 Nov 2007

Since the Colossus has over 2000 valves and a Dual-Core Intel 2 Processor has over a billion transistors it'll certainly be interesting to see the result. Any decent software would beat it hands down, I would have thought.

However, I'm being cynical and it's great to see such a fantastic machine up and running again. We owe it, and the people who worked on it, an awful lot.

  Forum Editor 19:53 15 Nov 2007

to be able to see this machine about halfway through the rebuild, and I must say it was very impressive. How anyone could set about rebuilding such a complex machine with nothing more to go on that a few photographs and the memories of some of the people who operated the original machine is quite beyond me.

  laurie53 20:30 15 Nov 2007

Saw a clip of it on the news.

I was brought up with thermionic valves, some as big as a litre bottle, but I've never seen anything like that!

  Cymro. 11:24 16 Nov 2007

Assuming that Colossus was state of the art at the time, what became of the British computer industry in the meantime?

Yes I know, it went down the drain just like all those other great inventions that we started but let others develop.

  octal 12:49 16 Nov 2007

Colossus isn't a computer in the true sense of the word as we know it, it's a number cruncher, it comprises of switches or gates, shift registers and biqinary counters, more like a pocket calculator but using valves.

It's got no memory, the clock is synced to the sprocket holes in the tape, so the faster the tape runs, the fast the machine calculates.
The actual circuits are very simple, they just comprise of Triode and Pentode valves and each circuit is built in modular form and duplicated then paralleled together.

Looking at the circuit I guess each module takes about 25 octal valves which take up quite a bit of room when they are mounted on a chassis, going by my old construction using valves I guess the chassis would be about 8inches by 19 inches which is the standard rack mounting used even to this day. Multiply all that lot up by X100 plus you get some idea of the size. I had a look the other day and I've still got some of those EF36 valves rattling around in a box in the loft at the moment.

It's a great achievement getting that machine going again before all those skills using valves are lost.

  TopCat® 13:31 16 Nov 2007

Possibly not memory as we understand it now but according to this link - click here - the machine had a form of memory: "Cracking the messages was a many-stage process. First, captured radio signals of the enciphered teleprinter messages were punched on to paper tape. This was fed at a rate of 5,000 characters per second into Colossus where it was held in the machine's memory....!

With regard to those spare valves, I understand they had a devil of a job sourcing many different types during the rebuild, so the museum people might be quite interested in purchasing them from you. The failure rate over time for these early 'transistors' was very high. TC.

  octal 13:54 16 Nov 2007

I might see if I dig them out when I'm next up in the hell hole.

I suppose the memory would be the tape, plus the state of the switches and registers at the time which would be all short term, it certainly would be long term memory like we would imagine, there just isn't the capacity.

From what I understand they used to run the same tape several times, each time refining the decryption, so it wasn't a one off process, if they had enough memory then it would have been a one time process.

  silverous 13:55 16 Nov 2007

It is impressive although I thought I read that they also had some detailed plans to work from also.

I would recommend anyone to visit Bletchley Park, it is just down the road from me and last time I went the fledgling computer museum was great as you could get up close to the whirring tape spools and punched cards and they had very old computers hooked up to screens that you could see working, very nostalgic (well apart from the spools of tape and punched cards - I'm not old enough for that to be nostalgia!)

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