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Leo III Logic Board

 Home > LEO Computers > Lyons Electronic Office (LEO) Archive > CCH LEO Artefacts Collection > Leo III Logic Board
 

One of the many logic boards that would have been installed in a LEO III computer.

Board no: S101/30N1/3; S101/30P2/3

Serial no: S006756

The board is part of our onsite display for the National Lottery Heritage-Funded LEO project.

The first LEO III was completed in 1961. This was a solid-state machine with a ferrite core memory. It was micro-programmed and was controlled by a multi-tasking operating system. LEO III was a new development, using new technology like transistors and core storage, allowing it to be much larger in capacity than LEO I and II. It had no magnetic drums or discs. It was a parallel machine with 40 bit adders, data paths and routes to autonomous input / output channels that avoided loading the central processor. Programs were loaded from magnetic tapes and there was an operating system, called the Master Routine, to allocate resources to programs, control the key facility of multi-programming (several programs in store but only one active at any instant in time with each program protected from interfering with another) and to provide an interface for the operators to deal with job initiation and any error conditions.
 
In 1963 LEO Computers Ltd was merged into English Electric Company and this led to the breaking up of the team that had inspired LEO computers. English Electric Company continued to build the LEO III, and went on to build the faster LEO 360 and even faster LEO 326 models, which had been designed by the LEO team before the takeover.
 
All LEO IIIs allowed concurrent running of as many as 12 application programs through the Master program operating system. Some were still in commercial use in British Telecom until 1981. Many users fondly remember the LEO III and enthuse about some of its quirkier features, such as having a loudspeaker connected to the central processor which enabled operators to tell if a program was looping by the distinctive sound it made.

Manufacturer: LEO Computers LTD
Date: early 1960s



Comment on This Page

Leo III Logic Board Articles:

Item Manufacturer Date
Barry Hooper, Programmer Shell Australia Unknown
Hackney Archives Unknown
Higher Systems Unknown
Early LEO I Programs Unknown
Secrets of Eastcote Government Office Site: The Customs Excise Years Unknown
Tomorrow's World Unknown
Graham Briscoe: Reminiscence Unknown
Dick Cromwell: LEO Memories Unknown
Ray Dawson: Reminiscences Unknown
Mike Finlay: Memories of LEO Unknown
John Simon Florentin, Computer Operator Unknown
David Holdsworth: Reminiscence Unknown
Maurice Bonney: Memoir LEO Unknown
Ron Marshall: Reminiscence Unknown
Ray Smith: Reminiscences of a LEO III Operator and Intercode Programmer Unknown
Anthony Robin Davies: Commentary LEO Unknown
Mike Tyzack's story with LEO computers Unknown
Faith Van Rooyen Unknown
Harry Warner: Reminiscence Unknown
Emil Gottwald: Reminisence LEO Unknown
Pat Whitaker: Commentary Unknown
Norman Witkin: Memoir of working with LEO in South Africa Unknown
Denis Hitchens: Reminiscence LEO Unknown
New Computers for the Post Office Unknown
Joe McNulty: Memoir LEO Unknown
Chris Reynolds: Memoir LEO Unknown
Mike Smith: Memoir LEO Unknown
Michael Wilson: Commentary LEO Unknown
Andrew Wylie Unknown
Nigel Furness: Reminiscence Unknown
I Love ICL Unknown
Museums Victoria, Melbourne Unknown
Peter Baker: Reminiscence Unknown
John Fletcher: Reminiscence Unknown
Brian Grimshaw: Reminiscence Unknown
Penny Woodward: Reminiscence Unknown
Chris Parker: Comment Unknown
Alison Taylor: Reminiscence Unknown
On-line Leo III User Manuals Unknown
Brian Skillen: Memories of my time operating LEO I Unknown
Explore our LEO Computers Collection Unknown
Who Else Used LEOs? 1951
How Many LEOs? 1951
Command by Magnetic Rings 21 Jul 1960
Advanced Data Processing 22 Jul 1960
Introducing LEO III 12 Aug 1960
Computers for Shell-Mex and BP 1962
Current Developments in Commercial Automatic Programming 1 Aug 1962
Wythenshawe: The Second Computer Centre for Shell-Mex and BP 1963
The Management of a Large Commercial Computer Bureau LEO 1964
An Introduction to Compiler Writing Jan 1965
Hardware in Europe May 1965
LEO III/32 at Colvilles Ltd, Ravenscraig Works 1967
The Brains Behind The Buttons 5 Jan 1967
Colvilles Technical Office Report Systems Development on the LEO III/32 Mar 1967
LEO III/7 Fire Sep 1967
LEO III: a rave from grave 4 Sep 1975
Interview with Les Turtle 1990
London’s Home Movies 2003
Timesharing History: the UK Story 2004
Report on visit of inspection to LEO III/ in Edinburgh Museum 2007
LEO Computer Reunion 2010 18 Apr 2010
LEO Computers in Australia LEO 2013
Software, A Progress Report on the LEO III Intercode and Master Routine Emulator LEO 2013
British transistor manufacturers in the 1950s 2016
John Page: Interview 11 Apr 2017
A Virtual LEO III 2018
Brian Hobson: Reminiscences LEO 18 Dec 2018
Software - LEO III 2020
Michael Hancock 2020
Michael Guy: LEO Master Routine 2020
John Daines: Reminiscence 2020
Robin Davies: Reminiscence 2020
John V Panter: Reminiscence 2020
Tom Brooks: Memoir LEO 2020
John Tomlinson: Memories 2021
Greg Wojtan: My Days with LEO 2021
Peter Guest: Reminiscence written by Margaret Guest 2021
Wendy Forward: Memoir by her daughter Anna C Page 2021
Bill Jack, English Electric Engineer (team leader) Ravenscraig LEO III, Recollection 2021
Helen Clark (Helen Jackson): Reminiscence Apr 2021
Stewart Logan: LEO III at Ravenscraig Nov 2021
Philip Cleary: Docos House, a reminiscence 8 Dec 2022

Magazines RELATED to Leo III Logic Board in our Library

Item Manufacturer Date
The Computer Journal July 1960 The British Computer Society Limited Jul 1960
The Computer Journal April 1962 The British Computer Society Limited Apr 1962
The Computer Journal April 1963 The British Computer Society Limited Apr 1963

Other Systems Related To Leo III Logic Board:

Item Manufacturer Date
Leo II Valve Rack LEO Computers LTD June 1959
Leo III Board LEO Computers LTD 1961
Leo III Digital Clock LEO Computers LTD 1961
55625 Program Wiring Subset Unit from LEO III LEO Computers Ltd c1965

This exhibit has a reference ID of CH52240. Please quote this reference ID in any communication with the Centre for Computing History.

 

Leo III Logic Board


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Articles

Introducing LEO III
LEO III/7 Fire
A Virtual LEO III
Software, A Progress Report on the LEO III Intercode and Master Routine Emulator
A LEO III: 21st Century Hindsight
LEO III Software Rescue
History of the Leo III Software Preservation Project: Blow by Blow Account
LEO III: a rave from grave
On-line Leo III User Manuals
Report on visit of inspection to LEO III/ in Edinburgh Museum
"Check Everything”: Validity and Correctness in LEO III
Ray Smith: Reminiscences of a LEO III Operator and Intercode Programmer
Software - LEO III
Bill Jack, English Electric Engineer (team leader) Ravenscraig LEO III, Recollection
Stewart Logan: LEO III at Ravenscraig
Colvilles Technical Office Report Systems Development on the LEO III/32
Colvilles Ltd., Ravenscraig Steelworks - Use of Lector OMR in LEO III systems
LEO III/32 at Colvilles Ltd, Ravenscraig Works

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