Deuce Magnetic Drum Store
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| Deuce magnetic drum store | |
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| Manufacturer | English Electric Co. |
| Production years | 1955-1964 |
Magnetic drum store from a Deuce computer made by English Electric for the NPL, 1955-1964
The Deuce computer was one of the earliest British commercially available computers. It was based on the National Physical Laboratory's "Pilot ACE", whose design evolved from A.M.Turing's 1945 "ACE Report". It was sold to many Universities and scientific establishments in the UK and abroad, being used for (e.g.) aircraft design, map making, nuclear research, and scheduling work for machines in a textile mill.
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[edit] How it works
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Please help improve this section by expanding it. |
The magnetic drum store is the place where the computer can store data when it is switched off. It was not used like a hard disk for all the programs and data files – these were stored on paper tape or punched cards. The drum store held the initial starting instructions which allow the machine to start and read programs and data off the tape or cards. The Deuce computer actually had two storage units: primary memory and secondary memory. Deuce’s primary memory consisted of delay lines; they were of limited capacity. The magnetic drum formed the secondary memory and, because it was of much larger capacity, was used to hold large data sets that the computer was working on that were too big for Deuce’s primary memory.
The Deuce computer read input data and programs from, and output results to, punched cards. Deuce’s primary memory consisted of mercury delay lines, 12 of which were "long", each holding 1024 bits, i.e. 32 words. Up to eight of the long delay lines were used to hold the instructions of a program while they were being executed. The total capacity of the delay lines was 402 words (the extra 18 words were held in "short" delay lines, which included 4 one-word delay lines each accessible in 32 µsec; the average access time to a word in a long delay line was 0.5 msec). The magnetic drum formed the secondary memory, and could hold 8192 words in 256 "tracks" of 32 words. Drum tracks could only be accessed by copying them to (or from) one of the long delay lines - locating and copying a track could take from 15 to 50 msec, depending on whether the drum read/write heads had to be moved first. The drum was used to hold data or instructions which exceeded the capacity of the delay line storage. However, unlike data held in disc storage on modern computers, information stored on the Deuce drum was only accessible while the program which had written it was still running; thus, each program could use the full capacity of the drum.
The drum shown above is of one used in the later production machines. The idea was for the drum to be in it's own, filtered air compartment. Scoring of the drum surface from dust particles was a major problem in the early days.
[edit] Memories
I was the maintenance engineer on the first Deuce delivered to RAE Farnborough.
My memories and those of over 400 people who worked on the Deuce in those early days can be read at http://users.tpg.com.au/eedeuce/people.html.
There are also photos, design and programming manuals and sales brochures on my
Deuce website at http://users.tpg.com.au/eedeuce/index.html.
— Anon
[edit] In the Science Museum
The Museum acquired this object in 1967 from the National Physical Laboratory. Inv. No: 1967-179.
This object is currently on display in the Dan Dare & the Birth of Hi-Tech Britain exhibition at the Science Museum, London.