The IBM 650 Magnetic Drum Data-Processing Machine is one of IBM's early computers, the world’s first mass-produced computer. It was announced in 1953 and in 1956 enhanced as the IBM 650 RAMAC with the addition of up to four disk storage units. 2,000 systems were produced, the last in 1962. Support for the 650 and its component units was withdrawn in 1969; the 650 was a two-address, bi-quinary coded decimal computer, with memory on a rotating magnetic drum. Character support was provided by the input/output units converting punched card alphabetical and special character encodings to/from a two-digit decimal code; the 650 was marketed to business and engineering users as well as to users of punched card machines who were upgrading from calculating punches, such as the IBM 604, to computers. Because of its low cost and ease of programming, the 650 was used to pioneer a wide variety of applications, from modeling submarine crew performance to teaching high school and college students computer programming.
The first 650 was installed on December 8, 1954 in the controller's department of the John Hancock Mutual Life Insurance Company in Boston. The IBM 7070, announced 1958, was expected to be a "common successor to at least the 650 and the 705"; the IBM 1620, introduced in 1959, addressed the lower end of the market. The UNIVAC Solid State was announced by Sperry Rand in December 1958 as a response to the 650. None of these had a 650 compatible instruction set; the basic 650 system consisted of three units: IBM 650 Console Unit housed the magnetic drum storage, arithmetical device and the operator's console. IBM 655 Power Unit IBM 533 or IBM 537 Card Read Punch Unit The IBM 533 had separate feeds for reading and punching. Weight: 5,400–6,263 pounds. Optional units: IBM 46 Tape To Card Punch, Model 3 IBM 47 Tape To Card Printing Punch, Model 3 IBM 355 Disk Storage Unit Systems with a disk unit were known as IBM 650 RAMAC Data Processing Systems IBM 407 Accounting Machine IBM 543 Card Reader Unit IBM 544 Card Punch Unit IBM 652 Control Unit IBM 653 Storage Unit IBM 654 Auxiliary Alphabetic Unit IBM 727 Magnetic Tape Unit IBM 838 Inquiry StationRotating drum memory provided 1,000, 2,000, or 4,000 words of memory at addresses 0000 to 0999, 1999, or 3999 respectively.
Words on the drums were organized in bands around the drum, fifty words per band, 20, 40, or 80 bands for the respective models. A word could be accessed when its location on the drum surface passed under the read/write heads during rotation; because of this timing, the second address in each instruction was the address of the next instruction. Instructions could be interleaved, placing many at addresses that would be accessible when execution of the previous instruction was completed. Instructions read from the drum went to a program register. Data read from the drum went through a 10-digit distributor; the 650 had a 20-digit accumulator, divided into 10-digit lower and upper accumulators with a common sign. Arithmetic was performed by a one-digit adder; the console, distributor and upper accumulators were all addressable. The optional IBM 653 Storage Unit, was introduced on May 3, 1955 providing up to five features: Magnetic tape controller Disk storage controller Sixty 10-digit words of magnetic core memory at addresses 9000 to 9059.
Three four-digit index registers at addresses 8005 to 8007. If the system had the 4000 word drum indexing was by adding 4000 to the first address for index register A, adding 4000 to the second address for index register B, by adding 4000 to each of the two addresses for index register C; the 4000-word systems required transistorized read/write circuitry for the drum memory and were available before 1963. Floating point – arithmetic instructions supported an eight-digit mantissa and two-digit characteristic – MMMMMMMMCC, providing a range of ±0.00000001E-50 to ±0.99999999E+49. The 650 instructions consisted of a two-digit operation code, a four-digit data address and the four-digit address of the next instruction; the sign was used on machines with optional features. The base machine had 44 operation codes. Additional operation codes were provided for options, such as floating point, core storage, index registers and additional I/O devices. With all options installed, there were 97 operation codes.
The Table lookup instruction could high-equal compare a referenced 10-digit word with 48 consecutive words on the same drum band in one 5ms revolution and switch to the next band in time for the next 48 w
Random-access memory is a form of computer data storage that stores data and machine code being used. A random-access memory device allows data items to be read or written in the same amount of time irrespective of the physical location of data inside the memory. In contrast, with other direct-access data storage media such as hard disks, CD-RWs, DVD-RWs and the older magnetic tapes and drum memory, the time required to read and write data items varies depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement. RAM contains multiplexing and demultiplexing circuitry, to connect the data lines to the addressed storage for reading or writing the entry. More than one bit of storage is accessed by the same address, RAM devices have multiple data lines and are said to be "8-bit" or "16-bit", etc. devices. In today's technology, random-access memory takes the form of integrated circuits. RAM is associated with volatile types of memory, where stored information is lost if power is removed, although non-volatile RAM has been developed.
Other types of non-volatile memories exist that allow random access for read operations, but either do not allow write operations or have other kinds of limitations on them. These include most types of ROM and a type of flash memory called NOR-Flash. Integrated-circuit RAM chips came into the market in the early 1970s, with the first commercially available DRAM chip, the Intel 1103, introduced in October 1970. Early computers used relays, mechanical counters or delay lines for main memory functions. Ultrasonic delay lines could only reproduce data in the order. Drum memory could be expanded at low cost but efficient retrieval of memory items required knowledge of the physical layout of the drum to optimize speed. Latches built out of vacuum tube triodes, out of discrete transistors, were used for smaller and faster memories such as registers; such registers were large and too costly to use for large amounts of data. The first practical form of random-access memory was the Williams tube starting in 1947.
It stored data. Since the electron beam of the CRT could read and write the spots on the tube in any order, memory was random access; the capacity of the Williams tube was a few hundred to around a thousand bits, but it was much smaller and more power-efficient than using individual vacuum tube latches. Developed at the University of Manchester in England, the Williams tube provided the medium on which the first electronically stored program was implemented in the Manchester Baby computer, which first ran a program on 21 June 1948. In fact, rather than the Williams tube memory being designed for the Baby, the Baby was a testbed to demonstrate the reliability of the memory. Magnetic-core memory was developed up until the mid-1970s, it became a widespread form of random-access memory. By changing the sense of each ring's magnetization, data could be stored with one bit stored per ring. Since every ring had a combination of address wires to select and read or write it, access to any memory location in any sequence was possible.
Magnetic core memory was the standard form of memory system until displaced by solid-state memory in integrated circuits, starting in the early 1970s. Dynamic random-access memory allowed replacement of a 4 or 6-transistor latch circuit by a single transistor for each memory bit increasing memory density at the cost of volatility. Data was stored in the tiny capacitance of each transistor, had to be periodically refreshed every few milliseconds before the charge could leak away; the Toshiba Toscal BC-1411 electronic calculator, introduced in 1965, used a form of DRAM built from discrete components. DRAM was developed by Robert H. Dennard in 1968. Prior to the development of integrated read-only memory circuits, permanent random-access memory was constructed using diode matrices driven by address decoders, or specially wound core rope memory planes; the two used forms of modern RAM are static RAM and dynamic RAM. In SRAM, a bit of data is stored using the state of a six transistor memory cell.
This form of RAM is more expensive to produce, but is faster and requires less dynamic power than DRAM. In modern computers, SRAM is used as cache memory for the CPU. DRAM stores a bit of data using a transistor and capacitor pair, which together comprise a DRAM cell; the capacitor holds a high or low charge, the transistor acts as a switch that lets the control circuitry on the chip read the capacitor's state of charge or change it. As this form of memory is less expensive to produce than static RAM, it is the predominant form of computer memory used in modern computers. Both static and dynamic RAM are considered volatile, as their state is lost or reset when power is removed from the system. By contrast, read-only memory stores data by permanently enabling or disabling selected transistors, such that the memory cannot be altered. Writeable variants of ROM share properties of both ROM and RAM, enabling data to persist without power and to be updated without requiring special equipment; these persistent forms of semiconductor ROM include USB flash drives, memory cards for cameras and portable devices, solid-state drives.
ECC memory includes special circuitry to detect and/or correct random faults (mem
Automatic Computing Engine
The Automatic Computing Engine was a British early electronic stored-program computer designed by Alan Turing. The project was managed by John R. Womersley, superintendent of the Mathematics Division of the National Physical Laboratory; the use of the word Engine was in homage to Charles Babbage and his Difference Engine and Analytical Engine. Turing's technical design Proposed Electronic Calculator was the product of his theoretical work in 1936 "On Computable Numbers" and his wartime experience at Bletchley Park where the Colossus computers had been successful in breaking German military codes. In his 1936 paper, Turing described his idea as a "universal computing machine", but it is now known as the Universal Turing machine. On 19 February 1946 Turing presented a detailed paper to the National Physical Laboratory Executive Committee, giving the first reasonably complete design of a stored-program computer. However, because of the strict and long-lasting secrecy around the Bletchley Park work, he was prohibited from explaining that he knew that his ideas could be implemented in an electronic device.
The better-known EDVAC design presented in the First Draft of a Report on the EDVAC, by John von Neumann, who knew of Turing's theoretical work, received much publicity, despite its incomplete nature and questionable lack of attribution of the sources of some of the ideas. Turing's report on the ACE was written in late 1945 and included detailed logical circuit diagrams and a cost estimate of £11,200, he felt that speed and size of memory were crucial and he proposed a high-speed memory of what would today be called 25 kilobytes, accessed at a speed of 1 MHz. The ACE implemented subroutine calls, whereas the EDVAC did not, what set the ACE apart from the EDVAC was the use of Abbreviated Computer Instructions, an early form of programming language, it was planned that Tommy Flowers, the engineer at the Post Office Research Station at Dollis Hill in north London, responsible for building the Colossus computers should build the ACE, but because of the secrecy around his wartime achievements and the pressure of post-war work, this was not possible.
Turing's colleagues at the NPL, not knowing about Colossus, thought that the engineering work to build a complete ACE was too ambitious, so the first version of the ACE, built was the Pilot Model ACE, a smaller version of Turing's original design. The Pilot ACE had 1450 thermionic valves, used mercury delay lines for its main memory; each of the 12 delay lines could store 32 instructions or data words of 32 bits. This ran its first program on 10 May 1950, at which time it was the fastest computer in the world with a clock speed of 1 MHz; the first production versions of the Pilot ACE, the English Electric DEUCE, of which 31 were sold, were delivered in 1955. A second implementation of the ACE design was the MOSAIC; this was built by Allen Coombs and William Chandler of Dollis Hill who had worked with Tommy Flowers on building the ten Colossus computers. It was installed at the Telecommunications Research Establishment which soon became the Royal Radar Establishment at Malvern and ran its first program in late 1952 or early 1953.
It was used to calculate aircraft trajectories from radar data. It continued operating until the early 1960s; the principles of the ACE design were used in the Bendix Corporation's G-15 computer. The engineering design was done by Harry Huskey who had spent 1947 in the ACE section at the NPL, he contributed to the hardware designs for the EDVAC. The first G-15 ran in 1954 and, as a small single-user machine, some consider it to be the first personal computer. Other derivatives of the ACE include the EMI Electronic Business Machine and the Packard Bell PB250. Carpenter, B. E.. "The other Turing machine", The Computer Journal, 20: 269–279, doi:10.1093/comjnl/20.3.269 Carpenter, B. E.. Jack, Colossus: The Secrets of Bletchley Park's Codebreaking Computers, Oxford: Oxford University Press, pp. 108–110, ISBN 978-0-19-284055-4 Lavington, Simon H. Early British Computers: The Story of Vintage Computers and The People Who Built Them, Manchester University Press Wilkinson, J. H. "Turing's Work at the National Physical Laboratory and the Construction of Pilot ACE, DEUCE and ACE", in Metropolis, Nicholas.
A History of Computing in the Twentieth Century, New York: Academic Press Yates, David M. Turing's Legacy: A History of Computing at the National Physical Laboratory, 1945-1995, London: Science Museum Oral history interview with Donald W. Davies, Charles Babbage Institute, University of Minnesota. Davies describes computer projects at the U. K. National Physical Laboratory, from the 1947 design work of Alan Turing to the development of the two ACE computers. Davies discusses a much larger, second ACE, the decision to contract with English Electric Company to build the DEUCE—possibly the first commercially produced computer in Great Britain. Events in the history of NPL — ACE computer
Drum memory was a magnetic data storage device invented by Gustav Tauschek in 1932 in Austria. Drums were used in the 1950s and into the 1960s as computer memory. For many early computers, drum memory formed the main working memory of the computer, it was so common that these computers were referred to as drum machines. Some drum memories were used as secondary storage. Drums were displaced as primary computer memory by magnetic core memory, a better balance of size, cost and potential for further improvements. Drums were replaced by hard disk drives for secondary storage, which were less expensive and denser; the manufacture of drums ceased in the 1970s. A drum memory contained a large metal cylinder, coated on the outside surface with a ferromagnetic recording material, it could be considered the precursor to the hard disk drive, but in the form of a drum rather than a flat disk. In most designs, one or more rows of fixed read-write heads ran along the long axis of the drum, one for each track.
The drum's controller selected the proper head and waited for the data to appear under it as the drum turned. Not all drum units were designed with each track having its own head. Some, such as the English Electric DEUCE drum and the Univac FASTRAND had multiple heads moving a short distance on the drum in contrast to modern HDDs, which have one head per platter surface; the performance of a drum with one head per track is determined entirely by the rotational latency, whereas in an HDD its performance includes a rotational latency delay plus the time to position the head over the desired track. In the era when drums were used as main working memory, programmers did optimum programming—the programmer positioned code on the drum in such a way as to reduce the amount of time needed for the next instruction to rotate into place under the head, they did this by timing how long it would take after loading an instruction for the computer to be ready to read the next one placing that instruction on the drum so that it would arrive under a head just in time.
This method of timing-compensation, called the "skip factor" or "interleaving", was used for many years in storage memory controllers. Tauschek's original drum memory had a capacity of about 500,000 bits. One of the earliest functioning computers to employ drum memory was the Atanasoff–Berry computer, it stored 3000 bits. The outer surface of the drum was lined with electrical contacts leading to capacitors contained within. Magnetic drums were developed for the US Navy during WW II with the work continuing at Engineering Research Associates in 1946 and 1947. An experimental study was completed at ERA and reported to the Navy on June 19, 1947. Other early drum storage device development occurred at Birkbeck College, Harvard University, IBM and the University of Manchester. An ERA drum was the internal memory for the Atlas 1 computer delivered to the US Navy in October 1950. Through mergers ERA became a division of UNIVAC shipping the Series 1100 drum as a part of the UNIVAC File Computer in 1956.
The first mass-produced computer, the IBM 650, had about 8.5 kilobytes of drum memory. As late as 1980, PDP-11/45 machines using magnetic core main memory and drums for swapping were still in use at many of the original UNIX sites. In BSD Unix and its descendants, /dev/drum was the name of the default virtual memory device, deriving from the use of drum secondary-storage devices as backup storage for pages in virtual memory. Drum memory is referenced in The Story of Mel, in which the skilled programmer Mel optimizes programs written for a drum memory computer by taking advantage of the time to process an instruction and the time for the drum to rotate so that the next instruction or data can be read, or optimizing in the opposite direction when the program should wait before proceeding. Magnetic drum memory units were used in the Minuteman ICBM launch control centers from the beginning in the early 1960s until the REACT upgrades in the mid-90's. CAB500 Karlqvist gap Manchester Mark 1 Random-access memory Wisconsin Integrally Synchronized Computer Carousel memory The Story of Mel: the classic story about one programmer's drum machine hand-coding antics: Mel Kaye.
Librascope LGP-30: The drum memory computer referenced in the above story referenced on Librascope LGP-30. Librascope RPC-4000: Another drum memory computer referenced in the above story Oral history interview with Dean Babcock
The Bendix G-15 computer was introduced in 1956 by the Bendix Corporation, Computer Division, Los Angeles, California. It weighs about 966 pounds; the base system, without peripherals, cost $49,500. A working model cost around $60,000, it could be rented for $1,485 per month. It was meant for industrial markets; the series was discontinued when Control Data Corporation took over the Bendix computer division in 1963. The chief designer of the G-15 was Harry Huskey, who had worked with Alan Turing on the ACE in the United Kingdom and on the SWAC in the 1950s, he made most of the design while working as a professor at Berkeley, other universities. David C. Evans was one of the Bendix engineers on the G-15 project, he would become famous for his work in computer graphics and for starting up Evans & Sutherland with Ivan Sutherland. The G-15 was inspired by the Automatic Computing Engine, it is a serial-architecture machine. It uses the drum as a recirculating delay line memory, in contrast to the analog delay line implementation in other serial designs.
Each track has a set of write heads. The length of delay, thus the number of words on a track, is determined by the spacing of the read and write heads, the delay corresponding to the time required for a section of the drum to travel from the write head to the corresponding read head. Under normal operation, data are written back without change, but this data flow can be intercepted at any time, allowing the machine to update sections of a track as needed; this arrangement allowed the designers to create "delay lines" of any desired length. In addition to the twenty "long lines" of 108 words each, there are four more short lines of four words each; these short lines recycle at 27 times the rate of the long lines, allowing fast access to needed data. The machine's accumulators are implemented as drum lines: three double-word lines are used for intermediate storage and double-precision addition and division in addition to a one single-word accumulator; this use of the drum rather than flip-flops for the registers helped to reduce vacuum tube count.
A consequence of this design was that, unlike other computers with magnetic drums, the G-15 does not retain its memory when it is shut off. The only permanent tracks are two timing tracks recorded on the drum at the factory; the second track is a backup, as the tracks are liable to erasure if one of their amplifier tubes shorted out. The serial nature of the G-15's memory was carried over into the design of its arithmetic and control circuits; the adders work on one binary digit at a time, the instruction word was designed to minimize the number of bits in an instruction that needed to be retained in flip-flops. The G-15 has 300 germanium diodes, it has a total of about 450 tubes. Its magnetic drum memory held 2,160 words of twenty-nine bits. Average memory access time is 14.5 milliseconds, but its instruction addressing architecture can reduce this for well-written programs. Its addition time is 270 microseconds. Single-precision multiplication took 2,439 microseconds and double-precision multiplication take 16,700 microseconds.
One of the G-15's primary output devices is the typewriter with an output speed of about 10 characters per second for numbers and about three characters per second for alphabetical characters. The machine's limited storage precludes much output of anything but numbers. A faster typewriter unit was available; the high-speed photoelectric paper tape reader read programs from tapes that were mounted in cartridges for easy loading and unloading. Not unlike magnetic tape, the paper tape data are blocked into runs of 108 words or less since, the maximum read size. A cartridge can contain up to 2500 words. While there was an optional high-speed paper tape punch for output, the standard punch operated at 17 hex characters per second. Optionally, the AN-1 "Universal Code Accessory" included the "35-4" Friden Flexowriter and HSR-8 paper tape reader and HSP-8 paper tape punch; the mechanical reader and punch can process paper tapes up to eight channels wide at 110 characters per second. The CA-1 "Punched Card Coupler" can connect one or two IBM 026 card punches to read cards at 17 columns per second or punch cards at 11 columns per second.
Full cards were processed more with an 80 column per second skip speed). The more expensive CA-2 Punched Card Coupler punches cards at a 100 card per minute rate; the PA-3 pen plotter runs at one inch per second with 200 increments per inch on a paper roll one foot wide by 100 feet long. The optional retractable pen-holder eliminates "retrace lines"; the MTA-2 can interface up to four drives for half-inch Mylar magnetic tapes, which can store as many as 300,000 words. The read/write rate is 430 hexadecimal digits per second.
Alan Mathison Turing was an English mathematician, computer scientist, cryptanalyst and theoretical biologist. Turing was influential in the development of theoretical computer science, providing a formalisation of the concepts of algorithm and computation with the Turing machine, which can be considered a model of a general-purpose computer. Turing is considered to be the father of theoretical computer science and artificial intelligence. Despite these accomplishments, he was never recognised in his home country during his lifetime, due to his homosexuality, a crime in the UK. During the Second World War, Turing worked for the Government Code and Cypher School at Bletchley Park, Britain's codebreaking centre that produced Ultra intelligence. For a time he led Hut 8, the section, responsible for German naval cryptanalysis. Here, he devised a number of techniques for speeding the breaking of German ciphers, including improvements to the pre-war Polish bombe method, an electromechanical machine that could find settings for the Enigma machine.
Turing played a pivotal role in cracking intercepted coded messages that enabled the Allies to defeat the Nazis in many crucial engagements, including the Battle of the Atlantic, in so doing helped win the war. Counterfactual history is difficult with respect to the effect Ultra intelligence had on the length of the war, but at the upper end it has been estimated that this work shortened the war in Europe by more than two years and saved over 14 million lives. After the war, Turing worked at the National Physical Laboratory, where he designed the Automatic Computing Engine, one of the first designs for a stored-program computer. In 1948, Turing joined Max Newman's Computing Machine Laboratory at the Victoria University of Manchester, where he helped develop the Manchester computers and became interested in mathematical biology, he wrote a paper on the chemical basis of morphogenesis and predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction, first observed in the 1960s.
Turing was prosecuted in 1952 for homosexual acts. He accepted chemical castration treatment, as an alternative to prison. Turing died 16 days before his 42nd birthday, from cyanide poisoning. An inquest determined his death as a suicide, but it has been noted that the known evidence is consistent with accidental poisoning. In 2009, following an Internet campaign, British Prime Minister Gordon Brown made an official public apology on behalf of the British government for "the appalling way he was treated". Queen Elizabeth II granted Turing a posthumous pardon in 2013; the Alan Turing law is now an informal term for a 2017 law in the United Kingdom that retroactively pardoned men cautioned or convicted under historical legislation that outlawed homosexual acts. Turing was born in Maida Vale, while his father, Julius Mathison Turing, was on leave from his position with the Indian Civil Service at Chatrapur in the Madras Presidency and presently in Odisha state, in India. Turing's father was the son of a clergyman, the Rev. John Robert Turing, from a Scottish family of merchants, based in the Netherlands and included a baronet.
Turing's mother, Julius' wife, was Ethel Sara Turing, daughter of Edward Waller Stoney, chief engineer of the Madras Railways. The Stoneys were a Protestant Anglo-Irish gentry family from both County Tipperary and County Longford, while Ethel herself had spent much of her childhood in County Clare. Julius' work with the ICS brought the family to British India, where his grandfather had been a general in the Bengal Army. However, both Julius and Ethel wanted their children to be brought up in Britain, so they moved to Maida Vale, where Alan Turing was born on 23 June 1912, as recorded by a blue plaque on the outside of the house of his birth the Colonnade Hotel. Turing had John. Turing's father's civil service commission was still active and during Turing's childhood years Turing's parents travelled between Hastings in England and India, leaving their two sons to stay with a retired Army couple. At Hastings, Turing stayed at Baston Lodge, Upper Maze Hill, St Leonards-on-Sea, now marked with a blue plaque.
The plaque was unveiled on 23 June 2012, the centenary of Turing's birth. Early in life, Turing showed signs of the genius that he was to display prominently, his parents purchased a house in Guildford in 1927, Turing lived there during school holidays. The location is marked with a blue plaque. Turing's parents enrolled him at St Michael's, a day school at 20 Charles Road, St Leonards-on-Sea, at the age of six; the headmistress recognised his talent early on. Between January 1922 and 1926, Turing was educated at Hazelhurst Preparatory School, an independent school in the village of Frant in Sussex. In 1926, at the age of 13, he went on to Sherborne School, a boarding independent school in the market town of Sherborne in Dorset; the first day of term coincided with the 1926 General Strike in Britain, but he was so determined to attend, that he rode his bicycle unaccompanied 60 miles from Southampton to Sherborne, stopping overnight at an inn. Turing's natural inclination towards mathematics and science did not earn him respect from some of the teachers at Sherborne, whose definition of education placed more emphasis on the classics.
His headmaster wrote to his parents: "I hope. If he is to stay at public school