Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!purdue!sxr
From: sxr@cs.purdue.EDU (Saul Rosen)
Newsgroups: comp.arch
Subject: Re: Mercury delay lines
Message-ID: <10814@medusa.cs.purdue.edu>
Date: 11 Jun 90 21:37:01 GMT
References: <3040@softway.oz> <2694@wrgate.WR.TEK.COM> <1990Jun7.210822.5230@esegue.segue.boston.ma.us> <2701@wrgate.WR.TEK.COM> <EaQvAbO00Ug7A7a68t@andrew.cmu.edu>
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Reply-To: sxr@babbage.cs.purdue.edu (Saul Rosen)
Organization: Department of Computer Science, Purdue University
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In article <EaQvAbO00Ug7A7a68t@andrew.cmu.edu> aw1r+@andrew.cmu.edu (Alfred Benjamin Woodard) writes:
>I've been following this thread for quite a long time and being a
>computer histroy / trivia buff I am curious what Mecury Delay lines
>were. It seems really weird reading about all the computers that used
>them and not knowing what they were,
>
>-ben

The Mercury Delay Line is not of real current interest in the
world of computer architecture, and there is not much point to
including a technical description here.  It is of course of great
historical interest, and is discussed in various books on the 
history of computers.  See for example "The Computer from Pascal to
von Neumann" by Herman H. Goldstine, and "A History of Computer
Technology" by M. R. Williams.  

The Mercury Delay Line memory was invented by J. Presper Eckert
at the Moore School of Electrical Engineering of the Univ. of
Pennsylvania in 1943-44.  The concept of the modern stored program
computer was introduced in the original design of the EDVAC in 1945.
The serial design of the EDVAC was based on the characteristics of the
Mercury Delay Line memory.  Maurice Wilkes attended a special course
on computers at the Moore School in the  summer of 1946, and he
went back to Cambridge in England and built a small Mercury Delay
Line computer, the EDSAC.  Eckert and John Mauchly left the Moore
School and formed a company which became the Eckert-Mauchly Computer
Corporation(EMCC). They built two Mercury Delay Line computers.  The first
was a relatively small one called the Binac.  Both the EDSAC and the
Binac were more or less finished in the spring of 1949.  There is some
argument about which was first. The EDVAC, much modified from its 
original design, was finished somewhat later.  

The most important Mercury Delay Line computer was the Univac, later
known as the Univac I.  It  was built by EMCC which was absorbed by
Remington-Rand.  There were a total of  46 Univac I systems delivered.
The Uni in Unisys is still a reference to Univac.
For a number of years the Mercury Delay Line was the only really
reliable  computer memory available,  and there were a fairly large
number of computers built that  used it.  In the US  there were the
Raytheon Raydac and the SEAC built by the National Bureau of
Standards.  A number of universities built computers based on the
SEAC, of  which the best known was the Midac at  the U. of Michigan.
In England the ACE and Pilot ACE led to a commercial DEUCE computer
using Mercury Delay Line memory that was marketed by English
Electric.