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From: bct@its63b.ed.ac.uk (B Tompsett)
Newsgroups: comp.arch
Subject: Re: An old fashioned memory technology, CRT's, how'd they work?
Message-ID: <523@its63b.ed.ac.uk>
Date: Wed, 15-Jul-87 08:27:06 EDT
Article-I.D.: its63b.523
Posted: Wed Jul 15 08:27:06 1987
Date-Received: Sat, 18-Jul-87 07:26:42 EDT
References: <602@madvax.UUCP>
Reply-To: bct@ecsvax.ed.ac.uk (B Tompsett)
Organization: Dept. of Computer Science, Edinburgh University, U.K.
Lines: 48

In article <602@madvax.UUCP> cw@madvax.UUCP (Carl Weidling) writes:
>
>	Yesterday I bought a book called "Bit by Bit, An Illustrated History
>of Computers", by Stan Augarten,Ticknor & Fields,NY,1984.
>
>  ... I was reading about the design of the Mark I in Manchester,England
>where it says: "He [F.C. Williams, the project's chief engineer] hit upon
>the idea of employing ordinary cathode ray tubes [to solve the problem of
>internal memory storage]..."
>	If anybody out there knows this stuff, I would be appreciative
>if you could enlighten me.

From:	Nigel Topham 

It was in December 1946 that Williams and Kilburn started work on the
CRT store, using commercially available CV1131 12-inch dia. CRTs [1].
The principle of a two-state electrostatic store can be visualised  from the
following simple experiment. Start with a focussed CRT beam and turn the
beam current on (thus producing a charged dot) and off again repeatedly.
Negative voltage pulses will be induced by capacitive coupling in a pick-up
plate placed close to the outer surface of the CRT screen. Now move the
beam whilst it is on so as to write a dash on the screen, then move the
beam back whilst the current is off, and then switch the then switch on the
current again. This time a positive pulse is induced. With dots and dashes
representing logcal O and 1, readable as negative and positive pulses, a
binary storage system is available.

Although the electrostatic charge leaks away in about 0.2 seconds this can
be refreshed in the same way that a modern MOS memory is refreshed.

By the Autumn of 1947 the Manchester group had successfully stored 2048 bits
of information for a period of several hours, and the way was clear to
construct a prototype computer - in Williams words "...to subject the
system to the most searching tests possible...".

(Editited excerpt from S.H.. Lavington, A History of Manchester Computers,
 NCC Publications, Manchester, England, 1975, pp. 7-10.)

[1] Williams, F.C., and Kilburn, T., "A Storage System for use with Binary
    Digital Computers", Proc IEE, vol. 96, pt. 2, no 30, 1949, pp. 183ff.
-- 
--
> Brian Tompsett. Department of Computer Science, University of Edinburgh,
> JCMB, The King's Buildings, Mayfield Road, EDINBURGH, EH9 3JZ, Scotland, U.K.
> Telephone:         +44 31 667 1081 x3332.
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