The Jim Austin Computer Collection
Marconi TAC
Transistorised Automatic Computer
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This is one of only 5 TAC machines originally developed by Marconi in 1959 for Radar (History of the Marconi Company 1874-1965, By W. J. Baker). It ran in Wyfla Nuclear power station on Anglesey, UK, from 1966 for 38 years (to 2004) (from 1968 non-stop), which could make it the longest running computer in the world. It was used to monitor the nuclear reactor.
It was originally a pair of machines. I have one of the pair, Bletchely park (national museum of computing) has the other half.
The following is text from the switch off report:
Wyfla Automatic Computer (TAC) leaves the station after 38 years.
1963 saw the construction begin of Wylfa Power Station. In 1965, English Electric commissioned Marconi to build a computer that could handle the monitoring and alarm system at Wylfa Power Station.
Work began initially in 1965 to assemble the system in Marconi's Head Office and then was moved in May 1966 to English Electric's Head Office in Kidsgrove. In October 1966, the computer was moved to Wylfa, and was given the name of Transistorised Automated Computer, which became known as TAC.
5 TAC's were built by Marconi, 2 of which were at Wylfa.
The TAC was kept in a room 100ft long, and had orange display screens, very different from today's PC screens.
Andy Corrigan, Station Manager said:
'The TAC has been an important part of equipment on site since the day the station was built. I am glad that both TAC's are going to [the jim Austin Collection] and [Blechely Park] where future generations can see how far technology has advanced in 40 years.'
Capell Aris notes:
I was the computer software specialist at Wylfa 1976-8. Your TAC timeline contains a trivial error: the Flexowriters were not replaced with line printers in 1977. All we did in that year (and really, into 1978) was to replace the drum stores with Dicoll RAM - I didn't have too much involvement with that project other than a minor rewrite to the operating system. I think the line printers replacements were fitted in 1979-80, which was after I'd moved on to Dinorwig.
I was the guy they honoured with turning the on-line machine off in 2004 - merely because I was the most decrepit person they could find!
[I have corrected the errors in the table below]
TAC timeline
1968 |
Switched on (24 hour operation since) |
1976 |
Display system replaced by modern raster scan system |
1977-78 |
Magnetic drum stores replaced by Dicoll Core Stores |
1979-80 |
Flexo writer mechanical typewriters and alarm strip printers replaced by modern line printers |
1981 |
Magnetic tape logging function transferred to PDP11 minicomputer |
1982 |
Alarm system function transferred to PDP11 minicomputer |
1985 |
Format display function transferred to PDP11 minicomputer |
1986 |
Analogue scanner input device control transferred from TAC to PDP11 minicomputer |
1988 |
BCD data transferred to PDP11 via TAC computer |
1993 |
BCD data transferred from TAC to LS11 Computer |
1996 |
BCD system control transferred from TAC to LS11 Computer |
2003 |
TAC Last Contact Scanner functions transferred to modern Alpha computer. Alpha transfers alarm data to PDP11. |
2004 |
SWITCHED OFF by Capell Aris |
This is the machine arriving:
and the console:
up right now on wheels 
TAC showing all units open. Left image is the core memory and drivers. Then there is the register store and then the microcode store, finally the power system. Below shows
the same from the cards side, rather tan the interconnections.
The control desk for computer 2 and the switch over desk.
This is how we got it upright! (with the help of Richard and trevor).
