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112-515: The concept of building a computer using an array of processors came to Daniel Slotnick while working as a programmer on the IAS machine in 1952. A formal design did not start until 1960, when Slotnick was working at Westinghouse Electric and arranged development funding under a US Air Force contract. When that funding ended in 1964, Slotnick moved to the University of Illinois Urbana–Champaign and joined

224-466: A fractal surface, such as rocks or soil, and are used by navigation radars. A radar beam follows a linear path in vacuum but follows a somewhat curved path in atmosphere due to variation in the refractive index of air, which is called the radar horizon . Even when the beam is emitted parallel to the ground, the beam rises above the ground as the curvature of the Earth sinks below the horizon. Furthermore,

336-422: A magnetic drum from Engineering Research Associates was later added. This drum had 80 tracks so two words could be read at a time, and each track stored 1,024 bits. While contemplating the drum's mechanism, Slotnik began to wonder if that was the correct way to build a computer. If the bits of a word were written serially to a single track, instead of in parallel across 40 tracks, then the data could be fed into

448-483: A mathematician is a stub . You can help Misplaced Pages by expanding it . Radar Radar is a system that uses radio waves to determine the distance ( ranging ), direction ( azimuth and elevation angles ), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track aircraft , ships , spacecraft , guided missiles , motor vehicles , map weather formations , and terrain . A radar system consists of

560-404: A transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna , a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about

672-424: A transmitter that emits radio waves known as radar signals in predetermined directions. When these signals contact an object they are usually reflected or scattered in many directions, although some of them will be absorbed and penetrate into the target. Radar signals are reflected especially well by materials of considerable electrical conductivity —such as most metals, seawater , and wet ground. This makes

784-499: A 24-bit parallel system that would be organized in a 256-by-32 arrangement. A single PE using this design was built in 1963. As the design work continued, the primary sponsor within the US Department of Defense was killed in an accident and no further funding was forthcoming. Looking to continue development, Slotnik approached Livermore, who at that time had been at the forefront of supercomputer purchases. They were very interested in

896-492: A bit-serial computer directly from the drum bit-by-bit. The drum would still have multiple tracks and heads, but instead of gathering up a word and sending it to a single ALU, in this concept the data on each track would be read a bit at a time and sent into parallel ALUs. This would be a word-parallel, bit-serial computer. Slotnick raised the idea at the IAS, but John von Neumann dismissed it as requiring "too many tubes". Slotnick left

1008-511: A colleague, John Cocke (better known as the inventor of RISC ), wrote a paper on the concept in 1958. After a short time at IBM and then another at Aeronca Aircraft , Slotnick ended up at Westinghouse's Air Arm division, which worked on radar and similar systems. Under a contract from the US Air Force 's RADC , Slotnik was able to build a team to design a system with 1,024 bit-serial ALUs, known as "processing elements" or PE's. This design

1120-840: A common noun, losing all capitalization . The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy , air-defense systems , anti-missile systems , marine radars to locate landmarks and other ships, aircraft anti-collision systems, ocean surveillance systems, outer space surveillance and rendezvous systems, meteorological precipitation monitoring, radar remote sensing , altimetry and flight control systems , guided missile target locating systems, self-driving cars , and ground-penetrating radar for geological observations. Modern high tech radar systems use digital signal processing and machine learning and are capable of extracting useful information from very high noise levels. Other systems which are similar to radar make use of other parts of

1232-482: A different dielectric constant or diamagnetic constant from the first, the waves will reflect or scatter from the boundary between the materials. This means that a solid object in air or in a vacuum , or a significant change in atomic density between the object and what is surrounding it, will usually scatter radar (radio) waves from its surface. This is particularly true for electrically conductive materials such as metal and carbon fibre, making radar well-suited to

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1344-535: A full radar system, that he called a telemobiloscope . It operated on a 50 cm wavelength and the pulsed radar signal was created via a spark-gap. His system already used the classic antenna setup of horn antenna with parabolic reflector and was presented to German military officials in practical tests in Cologne and Rotterdam harbour but was rejected. In 1915, Robert Watson-Watt used radio technology to provide advance warning of thunderstorms to airmen and during

1456-458: A lot of criticism when he chose Fairchild Semiconductor to produce the memory ICs, as at the time the production line was an empty room and the design existed only on paper. However, after three months of intense effort, Fairchild had a working design being produced en masse . As Slotnick would later comment, "Fairchild did a magnificent job of pulling our chestnuts out of the fire. The Fairchild memories were superb and their reliability to this day

1568-588: A mile from its operational site. ILLIAC was very late, very expensive, and never met its goal of producing 1 GFLOP. It was widely considered a failure even by those who worked on it; one stated simply that "any impartial observer has to regard Illiac IV as a failure in a technical sense." In terms of project management it is widely regarded as a failure, running over its cost estimates by four times and requiring years of remedial efforts to make it work. As Slotnik himself later put it: I'm bitterly disappointed, and very pleased... delighted and dismayed. Delighted that

1680-729: A physics instructor at the Imperial Russian Navy school in Kronstadt , developed an apparatus using a coherer tube for detecting distant lightning strikes. The next year, he added a spark-gap transmitter . In 1897, while testing this equipment for communicating between two ships in the Baltic Sea , he took note of an interference beat caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, but he did nothing more with this observation. The German inventor Christian Hülsmeyer

1792-495: A proposal for further intensive research on radio-echo signals from moving targets to take place at NRL, where Taylor and Young were based at the time. Similarly, in the UK, L. S. Alder took out a secret provisional patent for Naval radar in 1928. W.A.S. Butement and P. E. Pollard developed a breadboard test unit, operating at 50 cm (600 MHz) and using pulsed modulation which gave successful laboratory results. In January 1931,

1904-698: A pulsed system, and the first such elementary apparatus was demonstrated in December 1934 by the American Robert M. Page , working at the Naval Research Laboratory . The following year, the United States Army successfully tested a primitive surface-to-surface radar to aim coastal battery searchlights at night. This design was followed by a pulsed system demonstrated in May 1935 by Rudolf Kühnhold and

2016-442: A rescue. For similar reasons, objects intended to avoid detection will not have inside corners or surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking stealth aircraft . These precautions do not totally eliminate reflection because of diffraction , especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as chaff , are very reflective but do not direct

2128-399: A separate sixty-four slot 64-bit "scratchpad", LDB. There were four accumulators, AC0 through AC3, a program counter ILR, and various control registers. The system had a short instruction pipeline and implemented instruction look ahead . The PEs had about 12,000 gates. It included four 64-bit registers, using an accumulator A, an operand buffer B and a secondary scratchpad S. The fourth, R,

2240-413: A single CU, the new design had a total of 256 PEs arranged into four 64-PE "quadrants", each with its own CU. The CU's were also 64-bit designs, with sixty-four 64-bit registers and another four 64-bit accumulators. The system could run as four separate 64-PE machines, two 128-PE machines, or a single 256-PE machine. This allowed the system to work on different problems when the data was too small to demand

2352-502: A single very-high-speed vector processor . Similar to the ILLIAC in some ways, these processor designs loaded up many data elements into a single custom processor instead of a large number of specialized ones. The classic example of this design is the Cray-1 , which had performance similar to the ILLIAC. There was more than a little "backlash" against the ILLIAC design as a result, and for some time

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2464-503: A special purpose. One of these, RGR, was used for communicating data to neighbouring PEs, moving one "hop" per clock cycle. Another register, RGD, indicated whether or not that PE was currently active. "Inactive" PEs could not access memory, but they would pass results to neighbouring PEs using the RGR. The PEs were designed to work as a single 64-bit FPU, two 32-bit half-precision FPUs, or eight 8-bit fixed-point processors. Instead of 1,024 PEs and

2576-662: A system might do, Wilkins recalled the earlier report about aircraft causing radio interference. This revelation led to the Daventry Experiment of 26 February 1935, using a powerful BBC shortwave transmitter as the source and their GPO receiver setup in a field while a bomber flew around the site. When the plane was clearly detected, Hugh Dowding , the Air Member for Supply and Research , was very impressed with their system's potential and funds were immediately provided for further operational development. Watson-Watt's team patented

2688-514: A wide region and direct fighter aircraft towards targets. Marine radars are used to measure the bearing and distance of ships to prevent collision with other ships, to navigate, and to fix their position at sea when within range of shore or other fixed references such as islands, buoys, and lightships. In port or in harbour, vessel traffic service radar systems are used to monitor and regulate ship movements in busy waters. Meteorologists use radar to monitor precipitation and wind. It has become

2800-466: A write-once system that stored up to 1  Tbit on thin metal film coated on a strip of polyester sheet carried by a rotating drum. Construction of the new design began at Burroughs' Great Valley Lab. At the time, it was estimated the machine would be delivered in early 1970. After a year of working on the ICs, TI announced they had failed to be able to build the 64-pin designs. The more complex internal wiring

2912-855: A writeup on the apparatus was entered in the Inventions Book maintained by the Royal Engineers. This is the first official record in Great Britain of the technology that was used in coastal defence and was incorporated into Chain Home as Chain Home (low) . Before the Second World War , researchers in the United Kingdom, France , Germany , Italy , Japan , the Netherlands , the Soviet Union , and

3024-477: A year. On 6 January 1970, The Daily Illini , the student newspaper, claimed that the computer would be used to design nuclear weapons. In May, the Kent State shootings took place, and anti-war violence erupted across university campuses. Slotnick grew to be opposed to the use of the machine on classified research, and announced that as long as it was on the university grounds that all processing that took place on

3136-452: Is a simplification for transmission in a vacuum without interference. The propagation factor accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-world situation, pathloss effects are also considered. Frequency shift is caused by motion that changes the number of wavelengths between the reflector and the radar. This can degrade or enhance radar performance depending upon how it affects

3248-490: Is an excellent example of the MIMD concept. It was the better understanding of parallelism on ILLIAC that led to the improved compilers and programs that could take advantage of these designs. As one ILLIAC programmer put it, "If anybody builds a fast computer out of a lot of microprocessors, Illiac IV will have done its bit in the broad scheme of things." Most supercomputers of the era took another approach to higher performance, using

3360-451: Is as follows, where F D {\displaystyle F_{D}} is Doppler frequency, F T {\displaystyle F_{T}} is transmit frequency, V R {\displaystyle V_{R}} is radial velocity, and C {\displaystyle C} is the speed of light: Passive radar is applicable to electronic countermeasures and radio astronomy as follows: Only

3472-560: Is intended. Radar relies on its own transmissions rather than light from the Sun or the Moon, or from electromagnetic waves emitted by the target objects themselves, such as infrared radiation (heat). This process of directing artificial radio waves towards objects is called illumination , although radio waves are invisible to the human eye as well as optical cameras. If electromagnetic waves travelling through one material meet another material, having

ILLIAC IV - Misplaced Pages Continue

3584-558: Is interrupted by branches , which causes the PC to jump to one of two locations depending on a test, like whether a given memory address holds a non-zero value. In the ILLIAC design, each PE would be applying this test to different values, and thus have different outcomes. Since those values are private to the PE, the following instructions would need to be loaded based on a value only the PE knew. Daniel Slotnick Daniel Leonid Slotnick (1931–1985)

3696-471: Is just incredibly good." ILLIAC is considered to have dealt a death blow to magnetic-core memory and related systems like thin-film. Another indirect effect was caused by the complexity of the printed circuit boards (PCBs), or modules. At the original 25 MHz design speed, impedance in the ground wiring proved to be a serious problem, demanding that the PCBs be as small as possible. As their complexity grew,

3808-417: Is the range. This yields: This shows that the received power declines as the fourth power of the range, which means that the received power from distant targets is relatively very small. Additional filtering and pulse integration modifies the radar equation slightly for pulse-Doppler radar performance , which can be used to increase detection range and reduce transmit power. The equation above with F = 1

3920-416: The Cray-1 by nearly 12 months. Running at half its design speed, the one-quadrant ILLIAC IV delivered 50 MFLOP peak, making it the fastest computer in the world at that time. It is also credited with being the first large computer to use solid-state memory , as well as the most complex computer built to that date, with over 1 million gates. Generally considered a failure due to massive budget overruns,

4032-500: The Illinois Automatic Computer (ILLIAC) team. With funding from Advanced Research Projects Agency (ARPA), they began the design of a newer concept with 256 64-bit processors instead of the original concept with 1,024 1-bit processors. While the machine was being assembled by Burroughs , the university began building a new facility to house it. Political tension over the funding from the US Department of Defense led to

4144-623: The Nyquist frequency , since the returned frequency otherwise cannot be distinguished from shifting of a harmonic frequency above or below, thus requiring: Or when substituting with F D {\displaystyle F_{D}} : As an example, a Doppler weather radar with a pulse rate of 2 kHz and transmit frequency of 1 GHz can reliably measure weather speed up to at most 150 m/s (340 mph), thus cannot reliably determine radial velocity of aircraft moving 1,000 m/s (2,200 mph). In all electromagnetic radiation ,

4256-714: The RAF's Pathfinder . The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. It is thus used in many different fields where the need for such positioning is crucial. The first use of radar was for military purposes: to locate air, ground and sea targets. This evolved in the civilian field into applications for aircraft, ships, and automobiles. In aviation , aircraft can be equipped with radar devices that warn of aircraft or other obstacles in or approaching their path, display weather information, and give accurate altitude readings. The first commercial device fitted to aircraft

4368-732: The UIUC campus, originally called the Center for Advanced Computation but which is now the Astronomy Building. ILLIAC IV was constructed by Burroughs Corporation , using some special chips made by Fairchild Semiconductor . Because of campus unrest due to the Vietnam war, and the Mansfield amendments the ILLIAC IV was completed and installed at Ames Research Center instead of UIUC, and Slotnick's Darpa contract

4480-440: The electromagnetic spectrum . One example is lidar , which uses predominantly infrared light from lasers rather than radio waves. With the emergence of driverless vehicles, radar is expected to assist the automated platform to monitor its environment, thus preventing unwanted incidents. As early as 1886, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In 1895, Alexander Popov ,

4592-407: The reflective surfaces . A corner reflector consists of three flat surfaces meeting like the inside corner of a cube. The structure will reflect waves entering its opening directly back to the source. They are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect. Corner reflectors on boats, for example, make them more detectable to avoid collision or during

ILLIAC IV - Misplaced Pages Continue

4704-527: The "new boy" Arnold Frederic Wilkins to conduct an extensive review of available shortwave units. Wilkins would select a General Post Office model after noting its manual's description of a "fading" effect (the common term for interference at the time) when aircraft flew overhead. By placing a transmitter and receiver on opposite sides of the Potomac River in 1922, U.S. Navy researchers A. Hoyt Taylor and Leo C. Young discovered that ships passing through

4816-413: The 1920s went on to lead the U.K. research establishment to make many advances using radio techniques, including the probing of the ionosphere and the detection of lightning at long distances. Through his lightning experiments, Watson-Watt became an expert on the use of radio direction finding before turning his inquiry to shortwave transmission. Requiring a suitable receiver for such studies, he told

4928-671: The ARPA and the university fearing for the machine's safety. When the first 64-processor quadrant of the machine was completed in 1972, it was sent to the NASA Ames Research Center in California. After three years of thorough modification to fix various flaws, ILLIAC IV was connected to the ARPANET for distributed use in November 1975, becoming the first network-available supercomputer , beating

5040-704: The B6700 computer that connected to the machine through the same 1,024-bit-wide interface as the disk system. The machine consisted of a series of carrier chassis holding a number of the small modules. The majority of these were the Processing Units (PUs), which contained the modules for a single PE, its PEM, and the Memory Logic Unit that handled address translation and I/O. The PUs were identical, so they could be replaced or reordered as required. Each CU had about 30 to 40,000 gates. The CU had sixteen 64-bit registers and

5152-619: The CDC 7600 by two to six times, and it is generally credited as the fastest machine in the world until 1981. On 7 September 1981, after nearly 10 years of operation, the ILLIAC IV was turned off. The machine was officially decommissioned in 1982, and NASA's advanced computing division ended with it. One control unit and one processing element chassis from the machine is now on display at the Computer History Museum in Mountain View, less than

5264-585: The CU (or a unit within it, ADVAST) and another for the PEs. Instructions for the PEs were not decoded, and instead sent directly to the FINST register to be sent to the PEs to process. The ADVAST instructions were decoded and entered the CU's processing pipeline. Each quadrant contained 64 PEs and one CU. The CU had access to the entire I/O bus and could address all of the machine's memory. The PEs could only access their own local store,

5376-609: The IAS in February 1954 to return to school for his PhD and the matter was forgotten. After completing his PhD and some post-doc work, Slotnick ended up at IBM . By this time, for scientific computing at least, tubes and drums had been replaced with transistors and magnetic-core memory . The idea of parallel processors working on different streams of data from a drum no longer had the same obvious appeal. Nevertheless, further consideration showed that parallel machines could still offer significant performance in some applications; Slotnick and

5488-426: The PCBs had to add more and more layers in order to avoid growing larger. Eventually, they reached 15-layers deep, which proved to be well beyond the capabilities of draftsmen. The design was ultimately completed using new automated design tools provided by a subcontractor, and the complete design required two years of computer time on a Burroughs mainframe. This was a major step forward in computer aided design , and by

5600-507: The PDP-10. This caused further delays in bringing the machine online. The Illiac IV was contracted to be managed by ACTS Computing Corporation headquartered in Southfield, MI, a Timesharing and Remote Job Entry (RJE) company that had recently been acquired by the conglomerate, Lear Siegler Corporation . The DoD contracted with ACTS under a cost plus 10% contract. This unusual arrangement was due to

5712-472: The PEM, of 2,048 64-bit words. Both the PEs and CU could use load and store operations to access the disk system. The cabinets were so large that it required 240  ns for signals to travel from one end to the other. For this reason, the CU could not be used to coordinate actions, instead, the entire system was clock-synchronous with all operations in the PEs guaranteed to take the same amount of time no matter what

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5824-770: The United States, independently and in great secrecy, developed technologies that led to the modern version of radar. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain's radar development, Hungary and Sweden generated its radar technology during the war. In France in 1934, following systematic studies on the split-anode magnetron , the research branch of the Compagnie générale de la télégraphie sans fil (CSF) headed by Maurice Ponte with Henri Gutton, Sylvain Berline and M. Hugon, began developing an obstacle-locating radio apparatus, aspects of which were installed on

5936-533: The arrest of Oshchepkov and his subsequent gulag sentence. In total, only 607 Redut stations were produced during the war. The first Russian airborne radar, Gneiss-2 , entered into service in June 1943 on Pe-2 dive bombers. More than 230 Gneiss-2 stations were produced by the end of 1944. The French and Soviet systems, however, featured continuous-wave operation that did not provide the full performance ultimately synonymous with modern radar systems. Full radar evolved as

6048-475: The beam path caused the received signal to fade in and out. Taylor submitted a report, suggesting that this phenomenon might be used to detect the presence of ships in low visibility, but the Navy did not immediately continue the work. Eight years later, Lawrence A. Hyland at the Naval Research Laboratory (NRL) observed similar fading effects from passing aircraft; this revelation led to a patent application as well as

6160-523: The bus might refer to a memory location in the PE's PEM, a value in one of the PE registers, or a numeric constant. Since each PE had its own memory, while the instruction format and the CUs saw the entire address space, the system included an index register (X) to offset the base address. This allowed, for example, the same instruction stream to work on data that was not aligned in the same locations in different PEs. The common example would be an array of data that

6272-455: The complex system. At first, performance was dismal, with most programs running at about 15 MFLOPS, about three times the average for the CDC 7600 . Over time this improved, notably after Ames programmers wrote their own version of FORTRAN , CFD, and learned how to parallel I/O into the limited PEMs. On problems that could be parallelized the machine was still the fastest in the world, outperforming

6384-626: The constraint that no government employee could be paid more than a Congress person and many Illiac IV personnel made more than that limit. Dr. Mel Pirtle, with a background from the University of California, Berkeley and the Berkeley Computer Corporation (BCC) was engaged as the Illiac IV's director. When the machine first arrived, it could not be made to work. It suffered from all sorts of problems from cracking PCBs, to bad resistors , to

6496-411: The data needed to travel between more distant PEs. Each shift of data moved 64-words in a single 125 ns clock cycle. The system used a one-address format, in which the instructions included the address of one of the operands and the other operand was in the PE's accumulator (the A register). The address was sent to the PE's over a separate "broadcast" bus. Depending on the instruction, the value on

6608-483: The design but convinced him to upgrade the current design's fixed-point math units to true floating point , which resulted in the SOLOMON.2 design. Livermore would not fund development, instead, they offered a contract in which they would lease the machine once it was completed. Westinghouse management considered it too risky, and shut down the team. Slotnik left Westinghouse attempting to find venture capital to continue

6720-521: The design was instrumental in the development of new techniques and systems for programming parallel systems. In the 1980s, several machines based on ILLIAC IV concepts were successfully delivered. In June 1952, Daniel Slotnick began working on the IAS machine at the Institute for Advanced Study (IAS) at Princeton University . The IAS machine featured a bit-parallel math unit that operated on 40-bit words . Originally equipped with Williams tube memory,

6832-408: The detection of aircraft and ships. Radar absorbing material , containing resistive and sometimes magnetic substances, is used on military vehicles to reduce radar reflection . This is the radio equivalent of painting something a dark colour so that it cannot be seen by the eye at night. Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of

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6944-471: The detection process. As an example, moving target indication can interact with Doppler to produce signal cancellation at certain radial velocities, which degrades performance. Sea-based radar systems, semi-active radar homing , active radar homing , weather radar , military aircraft, and radar astronomy rely on the Doppler effect to enhance performance. This produces information about target velocity during

7056-411: The detection process. This also allows small objects to be detected in an environment containing much larger nearby slow moving objects. Doppler shift depends upon whether the radar configuration is active or passive. Active radar transmits a signal that is reflected back to the receiver. Passive radar depends upon the object sending a signal to the receiver. The Doppler frequency shift for active radar

7168-606: The device in patent GB593017. Development of radar greatly expanded on 1 September 1936, when Watson-Watt became superintendent of a new establishment under the British Air Ministry , Bawdsey Research Station located in Bawdsey Manor , near Felixstowe, Suffolk. Work there resulted in the design and installation of aircraft detection and tracking stations called " Chain Home " along the East and South coasts of England in time for

7280-538: The electric field is perpendicular to the direction of propagation, and the electric field direction is the polarization of the wave. For a transmitted radar signal, the polarization can be controlled to yield different effects. Radars use horizontal, vertical, linear, and circular polarization to detect different types of reflections. For example, circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces. Random polarization returns usually indicate

7392-479: The entire 256-PE array. Based on a 25 MHz clock, with all 256-PEs running on a single program, the machine was designed to deliver 1 billion floating point operations per second, or in today's terminology, 1  GFLOPS . This made it much faster than any machine in the world; the contemporary CDC 7600 had a clock cycle of 27.5 nanoseconds, or 36 MIPS, although for a variety of reasons it generally offered performance closer to 10 MIPS. To support

7504-473: The entire area in front of it, and then used one of Watson-Watt's own radio direction finders to determine the direction of the returned echoes. This fact meant CH transmitters had to be much more powerful and have better antennas than competing systems but allowed its rapid introduction using existing technologies. A key development was the cavity magnetron in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared

7616-434: The entire memory via a dedicated memory bus , whereas the PE's could only access their own PEM. To allow results from one PE to be used as inputs in another, a separate network connected each PE to its eight closest neighbours. Several testbed systems were constructed, including a 3-by-3 (9 PE) system and a 10-by-10 model with simplified PEs. During this period, some consideration was given to more complex PE designs, becoming

7728-461: The firm GEMA  [ de ] in Germany and then another in June 1935 by an Air Ministry team led by Robert Watson-Watt in Great Britain. In 1935, Watson-Watt was asked to judge recent reports of a German radio-based death ray and turned the request over to Wilkins. Wilkins returned a set of calculations demonstrating the system was basically impossible. When Watson-Watt then asked what such

7840-626: The help of Hans Mark , the director of the NASA Ames Research Center in what was becoming Silicon Valley , in January 1971 the decision was made to deliver the machine to Ames rather than the university. Located on an active US Navy base and protected by the U.S. Marines , security would no longer be a concern. The machine was finally delivered to Ames in April 1972, and installed in the Central Computer Facility in building N-233. By this point it

7952-410: The machine would be publicly released. He also grew increasingly concerned that the machine would be subject to attack by the more radical student groups. a position that seemed wise after the local students joined the 9 May 1970 nationwide student strike by declaring a "day of Illiaction", and especially the 24 August bombing of the mathematics building at the University of Wisconsin–Madison . With

8064-407: The machine's speed to about 200 MFLOPS. Together, these changes cost the project three years and $ 6 million. By 1969, the project was spending $ 1 million a month, and had to be spun out of the original ILLIAC team who were becoming increasingly vocal in their opposition to the project. By 1970, the machine was finally being built at a reasonable rate and it was being readied for delivery in about

8176-483: The machine, an extension to the Digital Computer Laboratory buildings were constructed. Sample work at the university was primarily aimed at ways to efficiently fill the PEs with data, thus conducting the first "stress test" in computer development. In order to make this as easy as possible, several new computer languages were created; IVTRAN and TRANQUIL were parallelized versions of FORTRAN , and Glypnir

8288-428: The market before ILLIAC was complete. As a result of this change, the individual PC boards grew about 1 inch (2.5 cm) square to about 6 by 10 inches (15 cm × 25 cm). This doomed Burroughs' efforts to produce a thin-film memory for the machine, because there was now no longer enough space for the memory to fit within the design's cabinets. Attempts to increase the size of the cabinets to make room for

8400-413: The memory caused serious problems with signal propagation. Slotnick surveyed the potential replacements and picked a semiconductor memory from Fairchild Semiconductor , a decision that was so opposed by Burroughs that a full review by ARPA followed. In 1969, these problems, combined with the resulting cost overruns from the delays, led to the decision to build only a single 64-PE quadrant, thereby limiting

8512-438: The mid-1970s such tools were commonplace. ILLIAC also led to major research into the topic of parallel processing that had wide-ranging effects. During the 1980s, with the price of microprocessors falling according to Moore's Law, a number of companies created MIMD (Multiple Instruction, Multiple Data) to build even more parallel machines, with compilers that could make better use of the parallelism. The Thinking Machines CM-5

8624-407: The most interesting. Burroughs was offering to build a new and much faster version of thin-film memory which would improve performance. TI was offering to build 64-pin emitter-coupled logic (ECL) integrated circuits (ICs) with 20 logic gates each. At the time, most ICs used 16-pin packages and had between 4 and 7 gates. Using TI's ICs would make the system much smaller. Burroughs also supplied

8736-562: The network, and some work was funded by Slotnick's DARPA contract. For example, a standard character set was established, and also the Purdy Polynomial , a secure hash function to protect passwords on ARPANET. Ironically, when the ILLIAC IV project was moved to Ames Research Center , the computer could only be accessed by telephone. He was awarded the AFIPS Prize in 1962 and was elected an IEEE Fellow in 1976. This article about

8848-623: The objects' locations and speeds. Radar was developed secretly for military use by several countries in the period before and during World War II . A key development was the cavity magnetron in the United Kingdom , which allowed the creation of relatively small systems with sub-meter resolution. The term RADAR was coined in 1940 by the United States Navy as an acronym for "radio detection and ranging". The term radar has since entered English and other languages as an anacronym ,

8960-494: The ocean liner Normandie in 1935. During the same period, Soviet military engineer P.K. Oshchepkov , in collaboration with the Leningrad Electrotechnical Institute , produced an experimental apparatus, RAPID, capable of detecting an aircraft within 3 km of a receiver. The Soviets produced their first mass production radars RUS-1 and RUS-2 Redut in 1939 but further development was slowed following

9072-492: The operands were. That way the CU could be sure that the operations were complete without having to wait for results or status codes. To improve the performance of operations that required the output of one PE's results to be used as the input to another PE, the PEs were connected directly to their neighbours, as well as the ones eight-steps away - for instance, PE1 was directly connected to PE0 and PE2, as well as PE9 and PE45. The eight-away connections allowed faster transport when

9184-520: The outbreak of World War II in 1939. This system provided the vital advance information that helped the Royal Air Force win the Battle of Britain ; without it, significant numbers of fighter aircraft, which Great Britain did not have available, would always have needed to be in the air to respond quickly. The radar formed part of the " Dowding system " for collecting reports of enemy aircraft and coordinating

9296-423: The overall objectives came out well in the end. Dismayed that it cost too much, took too long, doesn't do enough, and not enough people are using it. However, later analyses note that the project had several long-lasting effects on the computer market as a whole, both intentionally and unintentionally. Among the indirect effects was the rapid update of semiconductor memory after the ILLIAC project. Slotnick received

9408-469: The packaging of the TI ICs being highly sensitive to humidity. These issues were slowly addressed, and by the summer of 1973 the first programs were able to be run on the system although the results were highly questionable. Starting in June 1975, a concerted four-month effort began that required, among other changes, replacing 110,000 resistors, rewiring parts to fix propagation delay issues, improving filtering in

9520-399: The power supplies, and a further reduction in clock speed to 13 MHz. At the end of this process, the system was finally working properly. From then on, the system ran Monday morning to Friday afternoon, providing 60 hours of up-time for the users, but requiring 44 hours of scheduled downtime. Nevertheless, it was increasingly used as NASA programmers learned ways to get performance out of

9632-706: The primary tool for short-term weather forecasting and watching for severe weather such as thunderstorms , tornadoes , winter storms , precipitation types, etc. Geologists use specialized ground-penetrating radars to map the composition of Earth's crust . Police forces use radar guns to monitor vehicle speeds on the roads. Automotive radars are used for adaptive cruise control and emergency breaking on vehicles by ignoring stationary roadside objects that could cause incorrect brake application and instead measuring moving objects to prevent collision with other vehicles. As part of Intelligent Transport Systems , fixed-position stopped vehicle detection (SVD) radars are mounted on

9744-644: The project, but failed. Livermore would later select the CDC STAR-100 for this role, as CDC was willing to take on the development costs. When SOLOMON ended, Slotnick joined the Illinois Automatic Computer design (ILLIAC) team at the University of Illinois at Urbana-Champaign. Illinois had been designing and building large computers for the U.S. Department of Defense and the Advanced Research Projects Agency (ARPA) since 1949. In 1964

9856-432: The radial component of the velocity is relevant. When the reflector is moving at right angle to the radar beam, it has no relative velocity. Objects moving parallel to the radar beam produce the maximum Doppler frequency shift. When the transmit frequency ( F T {\displaystyle F_{T}} ) is pulsed, using a pulse repeat frequency of F R {\displaystyle F_{R}} ,

9968-414: The response. Given all required funding and development support, the team produced working radar systems in 1935 and began deployment. By 1936, the first five Chain Home (CH) systems were operational and by 1940 stretched across the entire UK including Northern Ireland. Even by standards of the era, CH was crude; instead of broadcasting and receiving from an aimed antenna, CH broadcast a signal floodlighting

10080-472: The responses, including Control Data , attempted to interest them in a vector processor design instead, but as these were already being designed the team was not interested in building another. In August 1966, eight-month contracts were offered to RCA , Burroughs , and Univac to bid on the construction of the machine. Burroughs eventually won the contract, having teamed up with Texas Instruments (TI). Both offered new technical advances that made their bid

10192-410: The resulting frequency spectrum will contain harmonic frequencies above and below F T {\displaystyle F_{T}} with a distance of F R {\displaystyle F_{R}} . As a result, the Doppler measurement is only non-ambiguous if the Doppler frequency shift is less than half of F R {\displaystyle F_{R}} , called

10304-427: The roadside to detect stranded vehicles, obstructions and debris by inverting the automotive radar approach and ignoring moving objects. Smaller radar systems are used to detect human movement . Examples are breathing pattern detection for sleep monitoring and hand and finger gesture detection for computer interaction. Automatic door opening, light activation and intruder sensing are also common. A radar system has

10416-407: The scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its radar cross-section . The power P r returning to the receiving antenna is given by the equation: where In the common case where the transmitter and the receiver are at the same location, R t = R r and the term R t ² R r ² can be replaced by R , where R

10528-456: The specialized disk drives , which featured a separate stationary head for every track and could offer speeds up to 500 Mbit/s and stored about 80 MB per 36" disk. They would also provide a Burroughs B6500 mainframe to act as a front-end controller, loading data from secondary storage and performing other housekeeping tasks. Connected to the B6500 was a 3rd party laser optical recording medium,

10640-540: The supercomputer market looked on massively parallel designs with disdain, even when they were successful. As Seymour Cray famously quipped, "If you were plowing a field, which would you rather use? Two strong oxen or 1024 chickens?" Each quadrant of the machine was 10 feet (3 m) high, 8 feet (2.4 m) deep and 50 feet (15 m) long. Arranged beside the quadrant was its input/output (I/O) system, whose disk system stored 2.5  GiB and could read and write data at 1 billion  bits per second , along with

10752-491: The target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a mirror . If the wavelength is much longer than the size of the target, the target may not be visible because of poor reflection. Low-frequency radar technology is dependent on resonances for detection, but not identification, of targets. This is described by Rayleigh scattering , an effect that creates Earth's blue sky and red sunsets. When

10864-569: The technology with the U.S. during the 1940 Tizard Mission . In April 1940, Popular Science showed an example of a radar unit using the Watson-Watt patent in an article on air defence. Also, in late 1941 Popular Mechanics had an article in which a U.S. scientist speculated about the British early warning system on the English east coast and came close to what it was and how it worked. Watson-Watt

10976-879: The transmitter. The reflected radar signals captured by the receiving antenna are usually very weak. They can be strengthened by electronic amplifiers . More sophisticated methods of signal processing are also used in order to recover useful radar signals. The weak absorption of radio waves by the medium through which they pass is what enables radar sets to detect objects at relatively long ranges—ranges at which other electromagnetic wavelengths, such as visible light , infrared light , and ultraviolet light , are too strongly attenuated. Weather phenomena, such as fog, clouds, rain, falling snow, and sleet, that block visible light are usually transparent to radio waves. Certain radio frequencies that are absorbed or scattered by water vapour, raindrops, or atmospheric gases (especially oxygen) are avoided when designing radars, except when their detection

11088-487: The two length scales are comparable, there may be resonances . Early radars used very long wavelengths that were larger than the targets and thus received a vague signal, whereas many modern systems use shorter wavelengths (a few centimetres or less) that can image objects as small as a loaf of bread. Short radio waves reflect from curves and corners in a way similar to glint from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between

11200-481: The university signed a contract with ARPA to fund the effort, which became known as ILLIAC IV, since it was the fourth computer designed and created at the university. Development started in 1965, and a first-pass design was completed in 1966. In contrast to the bit-serial concept of SOLOMON, in ILLIAC IV the PE's were upgraded to be full 64-bit (bit-parallel) processors, using 12,000 gates and 2048-words of thin-film memory . The PEs had five 64-bit registers, each with

11312-467: The use of radar altimeters possible in certain cases. The radar signals that are reflected back towards the radar receiver are the desirable ones that make radar detection work. If the object is moving either toward or away from the transmitter, there will be a slight change in the frequency of the radio waves due to the Doppler effect . Radar receivers are usually, but not always, in the same location as

11424-608: Was a 1938 Bell Lab unit on some United Air Lines aircraft. Aircraft can land in fog at airports equipped with radar-assisted ground-controlled approach systems in which the plane's position is observed on precision approach radar screens by operators who thereby give radio landing instructions to the pilot, maintaining the aircraft on a defined approach path to the runway. Military fighter aircraft are usually fitted with air-to-air targeting radars, to detect and target enemy aircraft. In addition, larger specialized military aircraft carry powerful airborne radars to observe air traffic over

11536-508: Was a similar conversion of ALGOL . Generally, these languages provided support for loading arrays of data "across" the PEs to be executed in parallel, and some even supported the unwinding of loops into array operations. In early 1966, the university sent out a request for proposals looking for industrial partners interested in building the design. Seventeen responses were received in July, seven responded, and of these three were selected. Several of

11648-500: Was an American mathematician and computer architect . Slotnick, in papers published with John Cocke in 1958, discussed the use of parallelism in numerical calculations for the first time. He later served as the chief architect of the ILLIAC IV supercomputer. He was the principal investigator on a DARPA contract in the early 1970s that produced the ILLIAC IV and the ARPANET . It was a fairly large operation, with its own building on

11760-477: Was causing crosstalk in the circuitry, and they asked for another year to fix the problems. Instead, the ILLIAC team chose to redesign the machine based on available 16-pin ICs. This required the system to run slower, using a 16 MHz clock instead of the original 25 MHz. The change from 64-pin to 16-pin cost the project about two years, and millions of dollars. TI was able to get the 64-pin design working after just over another year, and began offering them on

11872-487: Was given the name SOLOMON, after King Solomon , who was both very wise and had 1,000 wives. The PE's would be fed instructions from a single master central processing unit (CPU), the "control unit" or CU. SOLOMON's CU would read instructions from memory, decode them, and then hand them off to the PE's for processing. Each PE had its own memory for holding operands and results, the PE Memory module, or PEM. The CU could access

11984-494: Was loaded into different locations in the PEMs, which could then be made uniform by setting the index in the different PEs. In traditional computer designs, instructions are loaded into the CPU one at a time as they are read from memory. Normally, when the CPU completes processing an instruction, the program counter (PC) is incremented by one word and the next instruction is read. This process

12096-496: Was not renewed. In 1985, when IDA and NSA formed their supercomputing research facility in the DC area, Slotnick's widow donated his library to them. In 1987 the first issue of The Journal of Supercomputing contained a tribute to Slotnick. Most of the development of the ARPANET took place at MIT 's Lincoln Labs and BBN Technologies . However it was planned that ILLIAC IV would be on

12208-748: Was sent to the U.S. in 1941 to advise on air defense after Japan's attack on Pearl Harbor . Alfred Lee Loomis organized the secret MIT Radiation Laboratory at Massachusetts Institute of Technology , Cambridge, Massachusetts which developed microwave radar technology in the years 1941–45. Later, in 1943, Page greatly improved radar with the monopulse technique that was used for many years in most radar applications. The war precipitated research to find better resolution, more portability, and more features for radar, including small, lightweight sets to equip night fighters ( aircraft interception radar ) and maritime patrol aircraft ( air-to-surface-vessel radar ), and complementary navigation systems like Oboe used by

12320-456: Was several years late and well over budget at a total price of $ 31 million, almost four times the original estimate of $ 8 million for the complete 256-PE machine. NASA also decided to replace the B6500 front-end machine with a PDP-10 , which were in common use at Ames and would make it much easier to connect to the ARPAnet. This required the development of new software, especially compilers, on

12432-411: Was the first to use radio waves to detect "the presence of distant metallic objects". In 1904, he demonstrated the feasibility of detecting a ship in dense fog, but not its distance from the transmitter. He obtained a patent for his detection device in April 1904 and later a patent for a related amendment for estimating the distance to the ship. He also obtained a British patent on 23 September 1904 for

12544-508: Was used to broadcast or receive data from the other PEs. The PEs used a carry-lookahead adder , a leading-one detector for Boolean operations, and a barrel shifter . 64-bit additions took about 200 ns and multiplications about 400 ns. The PE's were connected to a private memory bank, the PEM, which held 2,048 64-bit words. Access time was on the order of 250 ns The PEs used a load/store architecture . The instruction set (ISA) contained two separate sets of instructions, one for

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