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From: haynes@ucscc.UCSC.EDU.ucsc.edu (99700000)
Newsgroups: comp.arch
Subject: Re: An old fashioned memory technology, CRT's, how'd they work?
Message-ID: <547@saturn.ucsc.edu>
Date: Wed, 15-Jul-87 21:08:23 EDT
Article-I.D.: saturn.547
Posted: Wed Jul 15 21:08:23 1987
Date-Received: Tue, 21-Jul-87 04:11:16 EDT
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Sender: usenet@saturn.ucsc.edu
Reply-To: haynes@ucscc.UCSC.EDU (Jim Haynes)
Organization: California State Home for the Weird
Lines: 30

Actually the original Williams tube used, I believe, perfectly ordinary
CR tubes, no flood gun inside and no special electrode inside.  Harry
Huskey here worked on these things, but he isn't handy for me to ask
just now.  Refreshing can be done with the same beam that does the
writing because the beam is randomly addressable, not scanning.  So you
only need to store the one bit per tube that you are currently reading.
In fact random access was the whole point, to avoid the time delays
inherent in delay-line storage.

IBM built its first marketed computers, 701 and 702, with this
technology; then quickly switched to cores and brought out the
704 and 705 with the rest of the hardware mostly the same, but
with somewhat different architecture.  (701 was fixed-point only,
704 added floating point; 701 stored instructions in half words,
704 used full word instructions, added index registers).

Williams tubes were also used in SWAC, which is the machine Harry
Huskey built for the Bureau of Standards branch on the UCLA campus.
They were also used in several other of the early computers built
by universities.  There's an old book "High Speed Computing Devices"
by Electronic Research Associates (a forerunner of Remington Rand
Univac) that may be in some libraries.

Seems like the flood guns and extra electrodes came later when people
realized that it would be possible to make oscilloscope CRTs with
arbitrarily-long persistence that way.  Hughes Aircraft used to make
CRTs and oscilloscopes with these technologies.
haynes@ucscc.ucsc.edu
haynes@ucscc.bitnet
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