Ferranti Mercury
Encyclopedia
The Mercury was an early 1950s commercial computer
built by Ferranti
. It was the successor to the Ferranti Mark 1, adding a floating point unit
for improved performance, and increased reliability by replacing the Williams tube
memory with core memory and using more solid state components. Nineteen Mercuries were sold before Ferranti moved on to newer designs.
system, which proved to break down all the time. Additionally, the machine used 4,200 thermionic valve
s that had to be replaced constantly. The Williams tubes, used as random access memory and registers, were reliable but required constant maintenance. As soon as the system went into operation, teams started looking at solutions to these problems.
One team decided to produce a much smaller and more cost-effective system built entirely with transistor
s. It first ran in November 1953 and is believed to be the first entirely transistor-based computer. Metropolitan-Vickers
later built this commercially as the Metrovick 950
, delivering seven.
s with solid state
diodes. After watching use of the Mark I they also realized that the users of computers were almost all in the sciences, and they decided to add a floating point unit to greatly improve performance in this role. Additionally the machine was to run at 1 MHz, eight times faster than the Mark I's 125 kHz, leading to the use of the name megacycle machine, and eventually Meg.
Meg first ran in May 1954. The use of solid state diodes reduced valve count by well over half, reducing the power requirements an equal amount from the Mark I's 25 kW to the Meg's 12 kW. Like the Mark I, Meg was based on a 10-bit "short word", combining two to form a 20-bit address and four to make a 40-bit integer. This was a result of the physical properties of the Williams tubes, which were used to make eight B-lines, or in modern terminology, accumulator
/index register
s. Meg could multiply two integers in about 60 microseconds. The floating point unit used three words for a 30-bit mantissa, and another as a 10-bit exponent. It could add two FP numbers in about 180 microseconds, and multiply them in about 360 µsec.
The first of an eventual 19 Mercury computers was delivered in August 1957. Manchester received one in February 1958, leasing half the time to commercial users via Ferranti's business unit. Both CERN
at Geneva and the Atomic Energy Research Establishment
at Harwell also installed theirs in 1958. A Mercury bought in 1959 was the UK Met Office
's first computer. The University of Buenos Aires
in Argentina received another one in 1960 .
The machine could run the Mercury Autocode
simplified coding system, later described by the new term "(high-level) programming language".
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
built by Ferranti
Ferranti
Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. Known primarily for defence electronics, the Company was once a constituent of the FTSE 100 Index but ceased trading in 1993.The...
. It was the successor to the Ferranti Mark 1, adding a floating point unit
Floating point unit
A floating-point unit is a part of a computer system specially designed to carry out operations on floating point numbers. Typical operations are addition, subtraction, multiplication, division, and square root...
for improved performance, and increased reliability by replacing the Williams tube
Williams tube
The Williams tube or the Williams-Kilburn tube , developed in about 1946 or 1947, was a cathode ray tube used to electronically store binary data....
memory with core memory and using more solid state components. Nineteen Mercuries were sold before Ferranti moved on to newer designs.
Mark I
When the Mark I started running in 1951 reliability was poor. The primary concern was the drum memoryDrum memory
Drum memory is a magnetic data storage device and was an early form of computer memory widely used in the 1950s and into the 1960s, invented by Gustav Tauschek in 1932 in Austria....
system, which proved to break down all the time. Additionally, the machine used 4,200 thermionic valve
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s that had to be replaced constantly. The Williams tubes, used as random access memory and registers, were reliable but required constant maintenance. As soon as the system went into operation, teams started looking at solutions to these problems.
One team decided to produce a much smaller and more cost-effective system built entirely with transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
s. It first ran in November 1953 and is believed to be the first entirely transistor-based computer. Metropolitan-Vickers
Metropolitan-Vickers
Metropolitan-Vickers, Metrovick, or Metrovicks, was a British heavy electrical engineering company of the early-to-mid 20th century formerly known as British Westinghouse. Highly diversified, they were particularly well known for their industrial electrical equipment such as generators, steam...
later built this commercially as the Metrovick 950
Metrovick 950
The Metrovick 950 was a transistorized computer, built from 1956 onwards by British company Metropolitan-Vickers, to the extent of six or seven machines, which were "used commercially within the company" or "mainly for internal use"...
, delivering seven.
Meg
Another team, including the main designers of the Mark I, started with a design very similar to the Mark I but replacing valves used as diodeDiode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
s with solid state
Solid state (electronics)
Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material...
diodes. After watching use of the Mark I they also realized that the users of computers were almost all in the sciences, and they decided to add a floating point unit to greatly improve performance in this role. Additionally the machine was to run at 1 MHz, eight times faster than the Mark I's 125 kHz, leading to the use of the name megacycle machine, and eventually Meg.
Meg first ran in May 1954. The use of solid state diodes reduced valve count by well over half, reducing the power requirements an equal amount from the Mark I's 25 kW to the Meg's 12 kW. Like the Mark I, Meg was based on a 10-bit "short word", combining two to form a 20-bit address and four to make a 40-bit integer. This was a result of the physical properties of the Williams tubes, which were used to make eight B-lines, or in modern terminology, accumulator
Accumulator (computing)
In a computer's central processing unit , an accumulator is a register in which intermediate arithmetic and logic results are stored. Without a register like an accumulator, it would be necessary to write the result of each calculation to main memory, perhaps only to be read right back again for...
/index register
Index register
An index registerCommonly known as a B-line in early British computers. in a computer's CPU is a processor register used for modifying operand addresses during the run of a program, typically for doing vector/array operations...
s. Meg could multiply two integers in about 60 microseconds. The floating point unit used three words for a 30-bit mantissa, and another as a 10-bit exponent. It could add two FP numbers in about 180 microseconds, and multiply them in about 360 µsec.
Mercury
Ferranti, which had built the Mark I for the university, continued development of the prototype Meg to produce the Mercury. The main change was to replace the Williams tubes with core memory. Although slower to access, at about 10 µsec for a 10-bit short word, the system required virtually no maintenance, considerably more important for commercial users. 1024×40-bits of core were provided, backed by four drums each holding 4096×40-bits. Much detailed information both about the Mercury hardware and the Autocode coding system is included in a downloadable Spanish-language Autocode manual.The first of an eventual 19 Mercury computers was delivered in August 1957. Manchester received one in February 1958, leasing half the time to commercial users via Ferranti's business unit. Both CERN
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...
at Geneva and the Atomic Energy Research Establishment
Atomic Energy Research Establishment
The Atomic Energy Research Establishment near Harwell, Oxfordshire, was the main centre for atomic energy research and development in the United Kingdom from the 1940s to the 1990s.-Founding:...
at Harwell also installed theirs in 1958. A Mercury bought in 1959 was the UK Met Office
Met Office
The Met Office , is the United Kingdom's national weather service, and a trading fund of the Department for Business, Innovation and Skills...
's first computer. The University of Buenos Aires
University of Buenos Aires
The University of Buenos Aires is the largest university in Argentina and the largest university by enrollment in Latin America. Founded on August 12, 1821 in the city of Buenos Aires, it consists of 13 faculties, 6 hospitals, 10 museums and is linked to 4 high schools: Colegio Nacional de Buenos...
in Argentina received another one in 1960 .
The machine could run the Mercury Autocode
Autocode
Autocode is the name of a family of "simplified coding systems", later called programming languages, devised in the 1950s and 1960s for a series of digital computers at the Universities of Manchester and Cambridge...
simplified coding system, later described by the new term "(high-level) programming language".