Misplaced Pages

#942057

65-397: The first prototype was built in 1970, and was among the first minicomputers small enough to fit in the back seat of a Volkswagen Beetle Convertible . It originally sold for $ 6,500 but after 18 months the price was dropped to $ 4995 to make it the only computer under $ 5000 available at that time. The standard -8/e included a processor, core memory, a data terminal, a tape control and drive,

130-406: A board only 1  square foot ( ~30 cm × 30 cm ). Of course, this also meant that the time needed to find a particular bit was somewhat longer as it travelled through the wire, and access times on the order of 500 microseconds were typical. Delay-line memory was far less expensive and far more reliable per bit than flip-flops made from tubes , and yet far faster than a latching relay . It

195-406: A clean signal inside the tube. Large transducers were used to generate a very tight beam of sound that would not touch the walls of the tube, and care had to be taken to eliminate reflections from the far end of the tubes. The tightness of the beam then required considerable tuning to make sure that both transducers were pointed directly at each other. Since the speed of sound changes with temperature,

260-478: A compressive wave that would flow to the other end, where it could be read. In effect, piezoelectric material simply replaced the mercury and transducers of a conventional mercury delay line with a single unit combining both. However, these solutions were fairly rare; growing crystals of the required quality in large sizes was not easy, which limited them to small sizes and thus small amounts of data storage. A better and more widespread use of piezoelectric delay lines

325-626: A delay line for a computer memory was invented by J. Presper Eckert in the mid-1940s for use in computers such as the EDVAC and the UNIVAC ;I . Eckert and John Mauchly applied for a patent for a delay-line memory system on October 31, 1947; the patent was issued in 1953. This patent focused on mercury delay lines, but it also discussed delay lines made of strings of inductors and capacitors , magnetostrictive delay lines, and delay lines built using rotating disks to transfer data to

390-413: A delay time is to implement a delay line in an integrated circuit storage device. This can be done digitally or with a discrete-time analogue method. The analogue one uses charge transfer devices (either bucket-brigade devices or charge-coupled devices ), which transport a stored electric charge stepwise from one end to the other. Both digital and analog methods are bandwidth limited at the upper end to

455-586: A few proprietary minicomputer architectures survive. The IBM System/38 operating system, which introduced many advanced concepts, lives on with IBM's AS/400 . Great efforts were made by IBM to enable programs originally written for the IBM System/34 and System/36 to be moved to the AS/400. After being rebranded multiple times, the AS/400 platform was replaced by IBM Power Systems running IBM i . In contrast, competing proprietary computing architectures from

520-502: A fixed distance from the antenna always return a signal after the same delay. This would appear as a fixed spot on the display, making detection of other targets in the area more difficult. Early radars simply aimed their beams away from the ground to avoid the majority of this "clutter". This was not an ideal situation; it required careful aiming, which was difficult for smaller mobile radars, and did not remove other sources of clutter-like reflections from features like prominent hills, and in

585-410: A programmers table, a line printer, software operating system and when purchased included installation, training and maintenance as part of the purchase agreement. The PDP-8/e featured a processor with single-address fixed word length, parallel transfer computer using 12-bit , two's complement arithmetic. The 1.2/1.4 microsecond cycle time provides a computation rate of 385,000 additions per second. It

650-409: A pulse to arrive at the receiving end was less than it would have been with a slower medium, such as air (343.2 m/s), but it also meant that the total number of pulses that could be stored in any reasonably sized column of mercury was limited. Other technical drawbacks of mercury included its weight, its cost, and its toxicity. Moreover, to get the acoustic impedances to match as closely as possible,

715-399: A quartz element with a powdered glass coating that reduced surface waves that interfered with proper reception. The United States Naval Research Laboratory used steel rods wrapped into a helix, but this was useful only for low frequencies under 1 MHz. Raytheon used a magnesium alloy originally developed for making bells. The first practical de-cluttering system based on the concept

SECTION 10

#1732781065943

780-409: A read head at one point on the circumference from a write head elsewhere around the circumference. The basic concept of the delay line originated with World War II radar research, as a system to reduce clutter from reflections from the ground and other non-moving objects. A radar system consists principally of an antenna, a transmitter, a receiver, and a display . The antenna is connected to

845-470: A result, less expensive. They were used in manufacturing process control, telephone switching and to control laboratory equipment. In the 1970s, they were the hardware that was used to launch the computer-aided design (CAD) industry and other similar industries where a small dedicated system was needed. The boom in worldwide seismic exploration for oil and gas in the early 1970s saw the widespread use of minicomputers in dedicated processing centres close to

910-489: A small, rectangular-shaped device. Electric delay lines are used for shorter delay times (nanoseconds to several microseconds). They consist of a long electric line or are made of discrete inductors and capacitors arranged in a chain. To shorten the total length of the line, it can be wound around a metal tube, getting some more capacitance against ground and also more inductance due to the wire windings, which are lying close together. Other examples are: Another way to create

975-502: A teleprinter and at least four thousand words of memory, that is capable of running programs in a higher level language, such as Fortran or BASIC . The class formed a distinct group with its own software architectures and operating systems. Minis were designed for control, instrumentation, human interaction, and communication switching as distinct from calculation and record keeping. Many were sold indirectly to original equipment manufacturers (OEMs) for final end-use application. During

1040-399: Is a type of smaller general-purpose computer developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors . In a 1970 survey, The New York Times suggested a consensus definition of a minicomputer as a machine costing less than US$ 25,000 (equivalent to $ 196,000 in 2023 ), with an input-output device such as

1105-448: Is seldom used today; the contemporary term for this class of system is " midrange computer ", such as the higher-end SPARC from Oracle , Power ISA from IBM , and Itanium -based systems from Hewlett-Packard . The term "minicomputer" developed in the 1960s to describe the smaller computers that became possible with the use of transistors and core memory technologies, minimal instructions sets and less expensive peripherals such as

1170-406: Is sometimes pointed to as an early example of a minicomputer, as it was small, transistorized and (relatively) inexpensive. However, its basic price of $ 100,000 (equivalent to $ 1,029,921 in 2023) and custom desk-like chassis places it within the "small system" or "midrange computer" category as opposed to the more modern use of the term minicomputer. Nevertheless, it retains a strong contender for

1235-606: The Friden EC-130 (1964) and EC-132, the Olivetti Programma ;101 desktop programmable calculator introduced in 1965, and the Litton Monroe Epic 2000 and 3000 programmable calculators of 1967. A similar solution to the magnetostrictive system was to use delay lines made entirely of a piezoelectric material, typically quartz. Current fed into one end of the crystal would generate

1300-566: The workstation machines opened new markets for graphics-based systems that the terminal-oriented minis could not even address. Minis retained a force for those using existing software products or those who required high-performance multitasking, but the introduction of newer operating systems based on Unix began to become highly practical replacements for these roles as well. For computational science , clusters of commodity PCs largely replaced minicomputers. Mini vendors began to rapidly disappear through this period. Data General responded to

1365-466: The ASR ;33. Another common difference was that most earlier small machines were not "general purpose", in that they were designed for a specific role like process control or accounting . On these machines, programming was generally carried out in their custom machine language , or even hard-coded into a plugboard , although some used a form of BASIC . DEC wrote, regarding their PDP-5, that it

SECTION 20

#1732781065943

1430-1292: The base software environment for the NonStop Servers, and has been extended to include support for Java and integration with popular development tools like Visual Studio and Eclipse . Later, Hewlett-Packard would split into HP and Hewlett-Packard Enterprise. The NonStop products and the DEC products would then be sold by HPE. A variety of companies emerged that built turnkey systems around minicomputers with specialized software and, in many cases, custom peripherals that addressed specialized problems such as computer-aided design , computer-aided manufacturing , process control , manufacturing resource planning , and so on. Many if not most minicomputers were sold through these original equipment manufacturers and value-added resellers . Several pioneering computer companies first built minicomputers, such as DEC , Data General , and Hewlett-Packard (HP) (who now refers to its HP3000 minicomputers as "servers" rather than "minicomputers"). And although today's PCs and servers are clearly microcomputers physically, architecturally their CPUs and operating systems have developed largely by integrating features from minicomputers. In

1495-458: The changing market by focusing entirely on the high-performance file server market, embracing a role within large LANs that appeared resilient. This did not last; Novell NetWare rapidly pushed such solutions into niche roles, and later versions of Microsoft Windows did the same to Novell. DEC decided to move into the large-computer space instead, introducing the VAX 9000 mainframe in 1989, but it

1560-472: The creation of an entire industry of minicomputer companies along Massachusetts Route 128 , including Data General , Wang Laboratories and Prime Computer . Other popular minis from the era were the HP 2100 , Honeywell 316 and TI-990 . Early minis had a variety of word sizes , with DEC's 12 and 18-bit systems being typical examples. The introduction and standardization of the 7-bit ASCII character set led to

1625-489: The data collection crews. Raytheon Data Systems RDS 704 and later RDS 500 were predominantly the systems of choice for nearly all the geophysical exploration as well as oil companies. At the launch of the MITS Altair 8800 in 1975, Radio Electronics magazine referred to the system as a "minicomputer", although the term microcomputer soon became usual for personal computers based on single-chip microprocessors . At

1690-459: The delay line used steel wires as the storage medium. Transducers were built by applying the magnetostrictive effect ; small pieces of a magnetostrictive material, typically nickel , were attached to either side of the end of the wire, inside an electromagnet . When bits from the computer entered the magnets, the nickel would contract or expand (based on the polarity) and twist the end of the wire. The resulting torsional wave would then move down

1755-403: The delay. This was relatively easy to arrange with simple electronics. After the war, Eckert turned his attention to computer development, which was a topic of some interest at the time. One problem with practical development was the lack of a suitable memory device, and Eckert's work on the radar delays gave him a major advantage over other researchers in this regard. For a computer application

1820-485: The early 1980s, such as DEC's VAX , Wang VS , and Hewlett-Packard's HP 3000 have long been discontinued without a compatible upgrade path. OpenVMS was ported to HP Alpha and Intel IA-64 ( Itanium ) CPU architectures, and now runs on x86-64 processors. Tandem Computers , which specialized in reliable large-scale computing, was acquired by Compaq in 1997, and in 2001 the combined entity merged with Hewlett-Packard . The NonStop Kernel-based NonStop product line

1885-420: The far end of the tube, where it would be read back out by the other transducer, inverted, and sent to the display. Careful mechanical arrangement was needed to ensure that the delay time matched the inter-pulse timing of the radar being used. All of these systems were suitable for conversion into a computer memory. The key was to restore and recycle the signals, so they would not disappear after traveling through

1950-484: The foundation for all current versions of Microsoft Windows , borrowed design ideas liberally from VMS . Many of the first generation of PC programmers were educated on minicomputer systems. Delay-line memory Delay-line memory is a form of computer memory , mostly obsolete, that was used on some of the earliest digital computers , and is reappearing in the form of optical delay lines . Like many modern forms of electronic computer memory, delay-line memory

2015-478: The half of the clock frequency, which determines the steps of transportation. In modern computers operating at gigahertz speeds, millimeter differences in the length of conductors in a parallel data bus can cause data-bit skew, which can lead to data corruption or reduced processing performance. This is remedied by making all conductor paths of similar length, delaying the arrival time for what would otherwise be shorter travel distances by using zig-zagging traces. In

PDP-8/e - Misplaced Pages Continue

2080-649: The later 1970s. Most mini vendors introduced their own single-chip processors based on their own architecture and used these mostly in low-cost offerings while concentrating on their 32-bit systems. Examples include the Intersil 6100 single-chip PDP-8, DEC T-11 PDP-11, microNOVA and Fairchild 9440 Nova, and TMS9900 TI-990. By the early 1980s, the 16-bit market had all but disappeared as newer 32-bit microprocessors began to improve in performance. Those customers who required more performance than these offered had generally already moved to 32-bit systems by this time. But it

2145-407: The mercury had to be kept at a constant temperature. The system heated the mercury to a uniform above-room temperature setting of 40 °C (104 °F), which made servicing the tubes hot and uncomfortable work. ( Alan Turing proposed the use of gin as an ultrasonic delay medium, claiming that it had the necessary acoustic properties. ) A considerable amount of engineering was needed to maintain

2210-423: The minicomputer class. Similar models using magnetic delay-line memory followed in the early 1960s. These machines, however, were essentially designed as small mainframes, using a custom chassis and often supporting only peripherals from the same company. In contrast, the machines that became known as minicomputers were often designed to fit into a standard chassis and deliberately designed to use common devices like

2275-533: The modern definition. Its introductory price of $ 18,500 (equivalent to $ 178,866 in 2023) places it in an entirely different market segment than earlier examples like the CDC 160. In contemporary terms, the PDP-8 was a runaway success, ultimately selling 50,000 examples. Follow-on versions using small scale integrated circuits further lowered the cost and size of the system. Its success led to widespread imitation, and

2340-496: The move to 16-bit systems, with the late-1969 Data General Nova being a notable entry in this space. By the early 1970s, most minis were 16-bit, including DEC's PDP-11 . For a time, "minicomputer" was almost synonymous with "16-bit", as the larger mainframe machines almost always used 32-bit or larger word sizes. As integrated circuit design improved, especially with the introduction of the 7400-series integrated circuits , minicomputers became smaller, easier to manufacture, and as

2405-547: The new RISC approach promised performance levels well beyond the fastest minis, and even high-end mainframes. All that really separated micros from the mini market was storage and memory capacity. Both of these began to be addressed through the later 1980s; 1 MB of RAM became typical by around 1987, desktop hard drives rapidly pushed past the 100 MB range by 1990, and the introduction of inexpensive and easily deployable local area network (LAN) systems provided solutions for those looking for multi-user systems. The introduction of

2470-410: The pulses by comparing to a master clock to find the particular bit it was looking for. Mercury was used because its acoustic impedance is close to that of the piezoelectric quartz crystals ; this minimized the energy loss and the echoes when the signal was transmitted from crystal to medium and back again. The high speed of sound in mercury (1450 m/s) meant that the time needed to wait for

2535-449: The same time, minis began to move upward in size. Although several 24 and 32-bit minis had entered the market earlier, it was DEC's 1977 VAX , which they referred to as a superminicomputer , or supermini, that caused the mini market to move en-masse to 32-bit architectures. This provided ample headroom even as single-chip 16-bit microprocessors like the TMS 9900 and Zilog Z8000 appeared in

2600-413: The signals from the output back into the input, creating a loop that maintains the signal as long as power is applied. The shaper ensures the pulses remain well-formed, removing any degradation due to losses in the medium. The memory capacity equals the time to transmit one bit divided by the recirculation time. Early delay-line memory systems had capacities of a few thousand bits (although the term "bit"

2665-471: The software context, the relatively simple OSs for early microcomputers were usually inspired by minicomputer OSs (such as CP/M 's similarity to Digital's single user OS/8 and RT-11 and multi-user RSTS time-sharing system). Also, the multiuser OSs of today are often either inspired by, or directly descended from, minicomputer OSs. UNIX was originally a minicomputer OS, while the Windows NT kernel ,

PDP-8/e - Misplaced Pages Continue

2730-543: The term "first minicomputer". Most computing histories point to the 1964 introduction of Digital Equipment Corporation 's (DEC) 12-bit PDP-8 as the first minicomputer. Some of this is no doubt due to DEC's widespread use of the term starting in the mid-1960s. Smaller systems, including those from DEC like the PDP-5 and LINC , had existed prior to this point, but it was the PDP-8 combination of small size, general purpose orientation and low price that puts it firmly within

2795-405: The time between pulses, or " pulse repetition frequency ". This resulted in the delayed signal from an earlier pulse exiting the delay unit the same time that the signal from a newer pulse was received from the antenna. One of the signals was electrically inverted, typically the one from the delay, and the two signals were then combined and sent to the display. Any signal that was at the same location

2860-403: The time, microcomputers were 8-bit single-user, relatively simple machines running simple program-launcher operating systems like CP/M or MS-DOS , while minis were much more powerful systems that ran full multi-user, multitasking operating systems, such as VMS and Unix . The Tandem Computers NonStop product line shipped its first fully fault-tolerant cluster computer in 1976. Around

2925-407: The timing was still critical, but for a different reason. Conventional computers have a clock period needed to complete an operation, which typically start and end with reading or writing memory. Thus the delay lines had to be timed such that the pulses would arrive at the receiver just as the computer was ready to read it. Many pulses would be in-flight through the delay, and the computer would count

2990-434: The transmitter, which sends out a brief pulse of radio energy before being disconnected again. The antenna is then connected to the receiver, which amplifies any reflected signals and sends them to the display. Objects farther from the radar return echos later than those closer to the radar, which the display indicates visually as a "blip", which can be measured against a scale in order to determine range. Non-moving objects at

3055-436: The tubes were heated in large ovens to keep them at a precise temperature. Other systems instead adjusted the computer clock rate according to the ambient temperature to achieve the same effect. EDSAC , the second full-scale stored-program digital computer , began operation with 256 35- bit words of memory, stored in 16 delay lines holding 560 bits each (words in the delay line were composed from 36 pulses, one pulse

3120-422: The two lines, a piezoelectric delay unit to delay the signal by a time that is equal to the duration of each line, 64 μs, is inserted in one of the two signal paths that are compared. In order to produce the required delay in a crystal of convenient size, the delay unit is shaped to reflect the signal multiple times through the crystal, thereby greatly reducing the required size of the crystal and thus producing

3185-468: The two-decade lifetime of the minicomputer class (1965–1985), almost 100 companies formed and only a half dozen remained. When single-chip CPU microprocessors appeared, beginning with the Intel 4004 in 1971, the term "minicomputer" came to mean a machine that lies in the middle range of the computing spectrum, in between the smallest mainframe computers and the microcomputers . The term "minicomputer"

3250-505: The ubiquitous Teletype Model 33 ASR. They usually took up one or a few 19-inch rack cabinets, compared with the large mainframes that could fill a room. In terms of relative computing power compared to contemporary mainframes, small systems that were similar to minicomputers had been available from the 1950s. In particular, there was an entire class of drum machines , like the UNIVAC 1101 and LGP-30 , that share some features of

3315-465: The wire just as the sound wave did down the mercury column. Unlike the compressive wave used in earlier devices, torsional waves are considerably more resistant to problems caused by mechanical imperfections, so much that the wires could be wound into a loose coil and pinned to a board. Due to their ability to be coiled, the wire-based systems could be as long as needed, so tended to hold considerably more data per unit; 1 kbit units were typical on

SECTION 50

#1732781065943

3380-416: The worst case would allow low-flying enemy aircraft to literally fly "under the radar". To filter out static objects, two pulses were compared, and returns with the same delay times were removed. To do this, the signal sent from the receiver to the display was split in two, with one path leading directly to the display and the second leading to a delay unit. The delay was carefully tuned to be some multiple of

3445-471: Was "the world’s first commercially produced minicomputer". It meets most definitions of "mini" in terms of power and size, but was designed and built to be used as an instrumentation system in labs, not as a general-purpose computer. Many similar examples of small special-purpose machines exist from the early 1960s, including the UK Ferranti Argus and Soviet UM-1NKh. The CDC 160 , circa 1960,

3510-400: Was a refreshable memory , but as opposed to modern random-access memory , delay-line memory was sequential-access . Analog delay line technology had been used since the 1920s to delay the propagation of analog signals. When a delay line is used as a memory device, an amplifier and a pulse shaper are connected between the output of the delay line and the input. These devices recirculate

3575-490: Was a flop in the market and disappeared after almost no sales. The company then attempted to enter the workstation and server markets with the DEC Alpha , but was too late to save the company and they eventually sold their remains to Compaq in 1998. By the end of the decade all of the classic vendors were gone; Data General , Prime , Computervision , Honeywell , and Wang , failed, merged, or were bought out. Today, only

3640-463: Was about 222  microseconds , which was considerably faster than the mechanical systems used on earlier computers. CSIRAC , completed in November 1949, also used delay-line memory. Some mercury delay-line memory devices produced audible sounds, which were described as akin to a human voice mumbling. This property gave rise to the slang term "mumble-tub" for these devices. A later version of

3705-642: Was built to be versatile and has a high capacity input/output that supports more than 60 types of peripherals . It could be used for a variety of tasks, from keeping score at Fenway Park to monitoring stimuli to the brain during brain surgery at Massachusetts General Hospital . The basic PDP-8/E system was a 10.5 x 19 x 24 inch (6 rack unit) rackmount or table top unit that contained the processor, core memory, front panel controls ("programmer's console"), console terminal interface for use with an external data terminal, and 115 or 230 volt AC power supply. Minicomputer A minicomputer , or colloquially mini ,

3770-479: Was developed by J. Presper Eckert at the University of Pennsylvania 's Moore School of Electrical Engineering . His solution used a column of mercury with piezo crystal transducers (a combination of speaker and microphone) at either end. Signals from the radar amplifier were sent to the transducer at one end of the tube, which would generate a small wave in the mercury. The wave would quickly travel to

3835-457: Was in European television sets. The European PAL standard for color broadcasts compares the signal from two successive lines of the image in order to avoid color shifting due to small phase shifts. By comparing two lines, one of which is inverted, the shifting is averaged, and the resulting signal more closely matches the original signal, even in the presence of interference. In order to compare

3900-399: Was not in popular use at the time), with recirculation times measured in microseconds . To read or write a particular memory address , it is necessary to wait for the signal representing its value to circulate through the delay line into the electronics. The latency to read or write any particular address is thus time and address dependent, but no longer than the recirculation time. Use of

3965-541: Was not long before this market also began to come under threat; the Motorola 68000 offered a significant percentage of the performance of a typical mini in a desktop platform. True 32-bit processors like the National Semiconductor NS32016 , Motorola 68020 and Intel 80386 soon followed. By the mid-1980s, high-end microcomputers offered CPU performance equal to low-end and mid-range minis, and

SECTION 60

#1732781065943

4030-405: Was nullified by the inverted signal from a previous pulse, leaving only the moving objects on the display. Several different types of delay systems were invented for this purpose, with one common principle being that the information was stored acoustically in a medium. MIT experimented with a number of systems, including glass, quartz, steel and lead. The Japanese deployed a system consisting of

4095-417: Was re-ported from MIPS processors to Itanium-based processors branded as ' HP Integrity NonStop Servers'. As in the earlier migration from stack machines to MIPS microprocessors, all customer software was carried forward without source changes. Integrity NonStop continues to be HP's answer for the extreme scaling needs of its very largest customers. The NSK operating system, now termed NonStop OS , continues as

4160-469: Was used as a space between consecutive numbers). The memory was later expanded to 512 words by adding a second set of 16 delay lines. In the UNIVAC I the capacity of an individual delay line was smaller, each column stored 120 bits, requiring seven large memory units with 18 columns each to make up a 1000-word store. Combined with their support circuitry and amplifiers , the memory subsystem formed its own walk-in room . The average access time

4225-637: Was used into the late 1960s, notably on commercial machines like the LEO ;I , Highgate Wood Telephone Exchange , various Ferranti machines, and the IBM 2848 Display Control . Delay-line memory was also used for video memory in early terminals, where one delay line would typically store 4 lines of characters (4 lines × 40 characters per line × 6 bits per character = 960 bits in one delay line). They were also used very successfully in several models of early desktop electronic calculator , including

#942057