ICT 1301
Encyclopedia
The ICT 1301 and its smaller derivative ICT 1300 were early business computers from International Computers and Tabulators
. Typical of mid-sized machines of the era they used core memory
, drum storage
and punched card
s, but they were unusual in that they were based on decimal logic instead of binary
.
The 1301 was the main machine in the line. Its main memory came in increments of 400 words of 48 bit
s (12 decimal digits) plus two parity bit
s. The maximum size was 2,000 words. It was the first ICT machine to use core memory.
Backing store was magnetic drum and optionally one inch, half inch or quarter inch wide magnetic tape
. Input was from 80 column punched cards and optionally 160 column punched cards and punched paper tape
. Output was to 80 column punched cards, printer
, and optionally to punched paper tape.
The machine ran at a clock speed
of 1 MHz and its arithmetic logic unit
(ALU) operated on data in a serial-parallel fashion — the 48 bit words were processed sequentially 4 bits at a time. A simple addition took 21 clock cycles; hardware multiplication averaged 170 clock cycles per digit; and division was performed in software.
It was announced in May 1960. The first customer delivery was in 1962, a 1301 sold to the University of London
. In total about 150 to 200 of these machines were sold. One of their main attractions was that they performed British currency calculations (pounds, shillings and pence
) in hardware. They also had the advantage of programmers not having to learn binary
or octal
arithmetic as the instruction set
was pure decimal and the arithmetic unit had no binary mode, only decimal or pounds, shillings and pence. The London University machine still exists (March 2011) and is being reinstated to working condition by a group of enthusiasts.
A typical 1301 requires 700 square feet (65 square metres) of floor space and weighs about 5 tons. It consumes about 13kVA
of three-phase electric power
. The electronics consist of over 4,000 printed circuit board
s each with many Germanium
diode
s (mainly OA5), Germanium transistor
s (mainly Mullard
GET872), resistor
s, capacitor
s and inductor
s. It contains no integrated circuit
s, though it does have a handful of thermionic valves
and a few dozen relay
s which work only at human speed when buttons are pressed.
The card punch could punch 100 cards per minute, again each card had 80 columns containing one character or a space.
The line printer could print 600 lines per minute. It used a print barrel made up of 120 print wheels each with 50 characters around its edge. Each of the 120 print positions had a print hammer which when fired squeezed the paper and an inked ribbon between itself and the rotating print barrel for a fraction of a second. It is reputed to be the first commercially produced barrel printer.
The drum could record 12,000 words of data. It also had 400 words of 'reserved' storage where the computer's bootstrap program (called Initial Orders) was stored. Up to 8 drums could be attached. Average access time was 5.7 ms.
TM4 tape decks could be connected and each ran at 75 inches per second, giving a throughput of 22,500 digits per second. Spools could hold up to 3600 feet (1,097.3 m) of tape and were of the three prong design not the later industry standard expanding hub design.
The 'High Speed' magnetic tape system (called tape type 1) used one inch (25.4mm) wide magnetic tape with sixteen tracks at a density of 300 bits per inch. Eight of the tracks held data and eight more tracks held checking data. This allowed single bit errors to be corrected and double bit errors to be detected. Up to eight tape decks could be connected and each ran at 150 inches per second, giving a throughput of 90,000 digits per second. Spools could hold up to 3600 feet (1,097.3 m) of tape and were of the three prong design common at the time for professional audio and video recorders.
One or two paper tape readers could be connected, each with a speed of 1,000 characters per second.
A paper tape punch of 300 characters per second was available.
An online teleprinter was available, though very few machines had these.
Towards the end of the working life span of the 1301, a single ICT standard interface could be added to allow data to written to the by then industry standard magnetic tape.
).
International Computers and Tabulators
International Computers and Tabulators or ICT was formed in 1959 by a merger of the British Tabulating Machine Company and Powers-Samas. In 1963 it also added the business computer divisions of Ferranti...
. Typical of mid-sized machines of the era they used core memory
Magnetic core memory
Magnetic-core memory was the predominant form of random-access computer memory for 20 years . It uses tiny magnetic toroids , the cores, through which wires are threaded to write and read information. Each core represents one bit of information...
, drum storage
Drum 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....
and punched card
Punched card
A punched card, punch card, IBM card, or Hollerith card is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions...
s, but they were unusual in that they were based on decimal logic instead of binary
Binary numeral system
The binary numeral system, or base-2 number system, represents numeric values using two symbols, 0 and 1. More specifically, the usual base-2 system is a positional notation with a radix of 2...
.
The 1301 was the main machine in the line. Its main memory came in increments of 400 words of 48 bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s (12 decimal digits) plus two parity bit
Parity bit
A parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code....
s. The maximum size was 2,000 words. It was the first ICT machine to use core memory.
Backing store was magnetic drum and optionally one inch, half inch or quarter inch wide magnetic tape
Magnetic tape
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...
. Input was from 80 column punched cards and optionally 160 column punched cards and punched paper tape
Punched tape
Punched tape or paper tape is an obsolete form of data storage, consisting of a long strip of paper in which holes are punched to store data...
. Output was to 80 column punched cards, printer
Line printer
The line printer is a form of high speed impact printer in which one line of type is printed at a time. They are mostly associated with the early days of computing, but the technology is still in use...
, and optionally to punched paper tape.
The machine ran at a clock speed
Clock signal
In electronics and especially synchronous digital circuits, a clock signal is a particular type of signal that oscillates between a high and a low state and is utilized like a metronome to coordinate actions of circuits...
of 1 MHz and its arithmetic logic unit
Arithmetic logic unit
In computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations.The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...
(ALU) operated on data in a serial-parallel fashion — the 48 bit words were processed sequentially 4 bits at a time. A simple addition took 21 clock cycles; hardware multiplication averaged 170 clock cycles per digit; and division was performed in software.
It was announced in May 1960. The first customer delivery was in 1962, a 1301 sold to the University of London
University of London
-20th century:Shortly after 6 Burlington Gardens was vacated, the University went through a period of rapid expansion. Bedford College, Royal Holloway and the London School of Economics all joined in 1900, Regent's Park College, which had affiliated in 1841 became an official divinity school of the...
. In total about 150 to 200 of these machines were sold. One of their main attractions was that they performed British currency calculations (pounds, shillings and pence
£sd
£sd was the popular name for the pre-decimal currencies used in the Kingdom of England, later the United Kingdom, and ultimately in much of the British Empire...
) in hardware. They also had the advantage of programmers not having to learn binary
Binary numeral system
The binary numeral system, or base-2 number system, represents numeric values using two symbols, 0 and 1. More specifically, the usual base-2 system is a positional notation with a radix of 2...
or octal
Octal
The octal numeral system, or oct for short, is the base-8 number system, and uses the digits 0 to 7. Numerals can be made from binary numerals by grouping consecutive binary digits into groups of three...
arithmetic as the instruction set
Instruction set
An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
was pure decimal and the arithmetic unit had no binary mode, only decimal or pounds, shillings and pence. The London University machine still exists (March 2011) and is being reinstated to working condition by a group of enthusiasts.
A typical 1301 requires 700 square feet (65 square metres) of floor space and weighs about 5 tons. It consumes about 13kVA
Volt-ampere
A volt-ampere is the unit used for the apparent power in an electrical circuit, equal to the product of root-mean-square voltage and RMS current. In direct current circuits, this product is equal to the real power in watts...
of three-phase electric power
Three-phase electric power
Three-phase electric power is a common method of alternating-current electric power generation, transmission, and distribution. It is a type of polyphase system and is the most common method used by grids worldwide to transfer power. It is also used to power large motors and other heavy loads...
. The electronics consist of over 4,000 printed circuit board
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
s each with many Germanium
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....
diode
Diode
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 (mainly OA5), Germanium 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 (mainly Mullard
Mullard
Mullard Limited was a British manufacturer of electronic components. The Mullard Radio Valve Co. Ltd. of Southfields, London, was founded in 1920 by Captain Stanley R. Mullard, who had previously designed valves for the Admiralty before becoming managing director of the Z Electric Lamp Co. The...
GET872), resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
s, capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
s and inductor
Inductor
An inductor is a passive two-terminal electrical component used to store energy in a magnetic field. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries...
s. It contains no integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
s, though it does have a handful of thermionic valves
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...
and a few dozen relay
Relay
A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal , or where several circuits must be controlled...
s which work only at human speed when buttons are pressed.
Standard Peripherals
The card reader was capable of reading 600 cards per minute, each with 80 columns containing one character or a space.The card punch could punch 100 cards per minute, again each card had 80 columns containing one character or a space.
The line printer could print 600 lines per minute. It used a print barrel made up of 120 print wheels each with 50 characters around its edge. Each of the 120 print positions had a print hammer which when fired squeezed the paper and an inked ribbon between itself and the rotating print barrel for a fraction of a second. It is reputed to be the first commercially produced barrel printer.
The drum could record 12,000 words of data. It also had 400 words of 'reserved' storage where the computer's bootstrap program (called Initial Orders) was stored. Up to 8 drums could be attached. Average access time was 5.7 ms.
Optional Peripherals
The 'standard' magnetic tape system (called tape type 3) used half inch (12.7mm) wide magnetic tape with ten tracks at a density of 300 bits per inch. Four of the tracks held data, four more tracks held the inverse of the data and there was a parity bit for both groups of four. This allowed single bit errors to be corrected and double bit errors to be detected. Up to eight AmpexAmpex
Ampex is an American electronics company founded in 1944 by Alexander M. Poniatoff. The name AMPEX is an acronym, created by its founder, which stands for Alexander M. Poniatoff Excellence...
TM4 tape decks could be connected and each ran at 75 inches per second, giving a throughput of 22,500 digits per second. Spools could hold up to 3600 feet (1,097.3 m) of tape and were of the three prong design not the later industry standard expanding hub design.
The 'High Speed' magnetic tape system (called tape type 1) used one inch (25.4mm) wide magnetic tape with sixteen tracks at a density of 300 bits per inch. Eight of the tracks held data and eight more tracks held checking data. This allowed single bit errors to be corrected and double bit errors to be detected. Up to eight tape decks could be connected and each ran at 150 inches per second, giving a throughput of 90,000 digits per second. Spools could hold up to 3600 feet (1,097.3 m) of tape and were of the three prong design common at the time for professional audio and video recorders.
One or two paper tape readers could be connected, each with a speed of 1,000 characters per second.
A paper tape punch of 300 characters per second was available.
An online teleprinter was available, though very few machines had these.
Towards the end of the working life span of the 1301, a single ICT standard interface could be added to allow data to written to the by then industry standard magnetic tape.
ICT 1300
The ICT 1300 was identical to the 1301 in every way except that its card reader was limited to 300 cards per minute and its line printer was limited to 300 lines per minute. It tended to be sold with less core storage and drum storage and without magnetic tape. A drum with only a quarter of the read/write heads fitted was commonly used giving just 3,000 words of 48 bits as backing storage.ICT 1302
The ICT 1302 was a larger version of the 1301 with the new ICT standard interface for connecting peripheral devices (the standard interface was later used on the ICT 1900 seriesICT 1900 series
ICT 1900 was the name given to a series of mainframe computers released by International Computers and Tabulators and later International Computers Limited during the 1960s and '70s...
).
External links
- ICT 1301 resurrection project This is "Flossie" the original machine sold to London University.
- YouTube video of computer running a demonstration Video of "Flossie" as she was in 2007.
- Pictures of the ICT 1301
- Picture of one of the prototype ICT 1301s