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From: aa1@j.cc.purdue.edu (Saul Rosen)
Newsgroups: comp.arch
Subject: Re: An old fashioned memory technology, CRT's, how'd they work?
Message-ID: <4770@j.cc.purdue.edu>
Date: Thu, 16-Jul-87 13:15:43 EDT
Article-I.D.: j.4770
Posted: Thu Jul 16 13:15:43 1987
Date-Received: Sat, 18-Jul-87 18:30:27 EDT
References: <602@madvax.UUCP>
Reply-To: aa1@j.cc.purdue.edu.UUCP (Saul Rosen)
Organization: Purdue University
Lines: 24

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]...Their operating principle was quite simple;
>"guns" in the bases of the tubes shot positively and negatively charged
>electrons at the faces of the tubes, thus storing bits in the form of charge
>spots, which, by the way, were quite visible to the eye."
>	Well, I have a problem with "positively and negatively charged
>electrons", but also, with how this can be memory.  How long did the charges
>last?  were they refreshed? How was the memory read after being stored?



Of course the statement you quote about Williams' tube memory sounds
like nonsense. No positively charged electrons!  The charged spot 
lasted about a fifth of a second.  It had to be regenerated at least
five times a second, and that provided a real memory.  Williams' tube
memory is described in all of the old books about computers.  One of
the more recent references is "A History of Computer Technology" by
Michael R. Williams, Prentice-Hall, 1985.