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76-644: Implemented in pMOS , as was common for the era, PACE required three supply voltages and an external clock with enough signal to drive the internal logic. This was normally supplied by the STE chip. Most PACE systems also required the BTE chip to convert the higher internal voltage signals to TTL levels used by the rest of the system. Its multiplexed address and data pins also required additional logic. Although National Semiconductor had second source agreements with Signetics and Rockwell Semiconductor , neither company produced

152-513: A 40-pin dual in-line package (DIP), originally in ceramic. As it was based on pMOS logic , the PACE series required three supply voltages, +5V (V SS , pin 20), +8V (V BB , pin 23) and -12V as the ground level (V GG , pin 29). The +8V level was normally supplied using simple electronics fed by the +5V line, thus reducing the complexity of the power supply . The chip was normally driven using an external 750 nanosecond clock (1.33 MHz) using

228-472: A Bidirectional Transceiver Element, BTE. This worked in conjunction with the PACE to produce a complete set of bus signals at TTL voltages that could then be used to easily interface with most contemporary devices like SRAM . In order to fit 16-bit addresses and data onto a 40-pin DIP, the same set of 16 pins was multiplexed between presenting an address and reading and writing data on separate cycles. This required

304-407: A current path between the positive supply and the output. PMOS gates have the same arrangement as NMOS gates if all the voltages are reversed. Thus, for active-high logic, De Morgan's laws show that a PMOS NOR gate has the same structure as an NMOS NAND gate and vice versa. Minicomputer A minicomputer , or colloquially mini , is a type of smaller general-purpose computer developed in

380-515: A direct address in memory. With R also set to zero, the address was within the base page, normally the first 256 bytes of memory. Setting R to 1 and X to 0 used the remaining eight bits as an offset from the PC. Setting the X bit to 1 turned on indexing, using the eight bits in addition to the values in the index registers, with R at 0 it would add the value in AC2, and setting it to 1 used AC3 instead. Normally

456-406: A drastically lower power consumption than either PMOS or NMOS. Even though a CMOS circuit had been proposed already in 1963 by Frank Wanlass and commercial 4000 series CMOS integrated circuits had entered production in 1968, CMOS remained complex to manufacture and allowed neither the integration level of PMOS or NMOS nor the speed of NMOS. It would take until the 1980s for CMOS to replace NMOS as

532-586: 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

608-406: A given value (in this case, zero), then branches back to the top if the condition is not met. The PACE's inherent skip-on-zero was a common feature of minis that sped loop performance by avoiding a separate test. When not appropriate, the increment or decrement could set the offset to zero to avoid triggering this feature. Continued improvement in semiconductor fabrication in the early 1970s led to

684-399: A number of fixes to problems found in the PACE. Notable among these was a problem with the interrupt that was triggered when the stack filled. In the PACE this did not work properly; if the interrupt arrived at exactly the same time as a NIR3 or NIR5, the wrong interrupt code would be called from location 0 rather than 2. National Semiconductor suggested either not using this feature, or placing

760-545: A redesign of the PACE in nMOS to create the INS8900. The new version retained much of the original chip layout, although, unsurprisingly, some of the power supply pins changed their inputs; the original +5V V SS was now ground (GND), V BB changed from -8 to +8V, and the former -12V V GG became the +12V V DD . For reasons unknown, two other pins did not change function but did change name; CLK became V CC and NCLK became CLKX. The most important change in terms of usage

836-448: A resistor, so the whole circuit can be made with PMOS FETs), it has several shortcomings as well. The worst problem is that there is a direct current (DC) through a PMOS logic gate when the so-called "pull-up network" (PUN) is active, that is, whenever the output is high, which leads to static power dissipation even when the circuit sits idle. Also, PMOS circuits are slow to transition from high to low. When transitioning from low to high,

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912-470: 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

988-410: A single INS8208 buffering the control signals that indicated whether the bus was in address or data mode (among other things), two more INS8208's to each buffer 8-bits of data, and two INS8212 to each latch 8-bits of the address. Another change made possible by the lower loads in nMOS was that clock signals no longer required as much power. This eliminated the need for the STE, which could be replaced by

1064-480: A single operation. PMOS logic PMOS or pMOS logic (from p-channel metal–oxide–semiconductor ) is a family of digital circuits based on p-channel , enhancement mode metal–oxide–semiconductor field-effect transistors (MOSFETs). In the late 1960s and early 1970s, PMOS logic was the dominant semiconductor technology for large-scale integrated circuits before being superseded by NMOS and CMOS devices. Mohamed Atalla and Dawon Kahng manufactured

1140-545: A suitable crystal and a single 7404 inverter , available from many manufacturers. As the external clock was no longer high-power, only one clock input was needed, the former NCLK, now renamed CLKX. The former second phase was now generated onboard the CPU. These changes also allowed the system to run at a higher speed, a 2 MHz crystal was recommended, increasing fairly significantly from the PACE's 1.33. This improved instruction times to 8 to 20 microseconds. Other changes included

1216-446: A value in memory and were commonly used to implement loops, thus indirect addressing was common as the control variable for the loop might be located outside the code block. Another interesting feature of these instructions was that (in any addressing mode) if the value was changed to zero, the SK ip instruction was called. This allowed loops to be exited without any additional tests; typically

1292-486: Is automatically incremented and decremented when PUSH and PULL instructions are encountered. The Program Counter (PC) is automatically pushed or pulled to the stack during subroutine calls and returns. Additional instructions allows the four registers and the Status and Control Flag Register to be pushed and pulled as well. PACE has ten 16-bit internal locations that hold the topmost stack values. A unique feature of

1368-439: 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

1444-613: Is more common in minicomputers where there are enough available status bits, as it allows the two to be tracked separately during a series of shift/rotate and add instructions, which is a common sequence. The IN EN flag, normally 1, allows interrupts to be enabled or disabled. One unique feature of the PACE, not present in the IMP-16, is the BYTE flag. When this is turned on, data is accessed in 8 bit words instead of 16. This allows for easier processing of 8-bit data like ASCII text. The rest of

1520-448: 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

1596-406: 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

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1672-520: The electron mobility in the n-type channel of NMOS MOSFETs is about three times that of the hole mobility in the p-type channel of PMOS MOSFETS, NMOS logic allows for an increased switching speed. For this reason NMOS logic quickly began to replace PMOS logic. By the late 1970s, NMOS microprocessors had overtaken PMOS processors. PMOS logic remained in use for a while due to its low cost and relatively high level of integration for applications such as simple calculators and clocks. CMOS technology promised

1748-566: 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

1824-468: The 4004 uses positive supply voltage V SS =+5V and negative supply voltage V DD = -10V. The p-type MOSFETs are arranged in a so-called "pull-up network" (PUN) between the logic gate output and positive supply voltage, while a resistor is placed between the logic gate output and the negative supply voltage. The circuit is designed such that if the desired output is high, then the PUN will be active, creating

1900-466: 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

1976-510: The Base Page was the first 256 bytes of memory, but when the BPS pin was asserted it instead split the base page between the first and last 128 bytes. The idea was that external devices would be mapped onto these high memory locations, and could easily watch for writes and reads by examining the address on the bus and seeing if the top nine bits were all 1's. Oddly, there is no instruction to change

2052-791: The Intel 1101, in 1969. The 1024-bit dynamic random-access memory Intel 1103 followed in 1970. The 1103 was a commercial success and quickly began replacing magnetic core memory in computers. Intel introduced its first PMOS microprocessor , the Intel 4004 , in 1971. A number of companies followed Intel's lead. Most early microprocessors were manufactured in PMOS technology: 4040 and 8008 from Intel; IMP-16 , PACE and SC/MP from National Semiconductor ; TMS1000 from Texas Instruments ; PPS-4 and PPS-8 from Rockwell International . There are several commercial firsts in this list of microprocessors:

2128-517: The MOSFET offers a number of advantages: Disadvantages relative to bipolar integrated circuits were: General Microelectronics introduced the first commercial PMOS circuit in 1964, a 20-bit shift register with 120 MOSFETs – at the time an incredible level of integration. The attempt by General Microelectronics in 1965 to develop a set of 23 custom integrated circuits for an electronic calculator for Victor Comptometer proved to be too ambitious given

2204-462: The PACE design. The PACE was followed by the INS8900 , which had the same architecture but was implemented in nMOS . This version made electrical interfacing easier and also fixed several bugs in the PACE logic and increased the speed about 50%. By the time it was available, higher-performance 16-bit CPUs were appearing, and the company began to deemphasize sales of the line. The PACE was packaged in

2280-421: The PACE is that after the stack is almost full and another push is attempted, or it is empty after a pull is attempted, an interrupt is generated. This is normally used to call interrupt handler code that copies some or all of the values to or from the stack into main memory . This allows the internal stack registers to be used like a cache of a larger memory-based stack. The Status and Control Flag register

2356-496: The System Timing Element, STE, chip to produce signals of the required signal strength. As these signals were also used by external devices, the clock signals were at TTL levels, +5V, in contrast to most pins which were at +8V. As the external signals were presented at the +8V, interfacing the system with common devices working at TTL levels was not trivial. For this reason, systems using the PACE normally included

National Semiconductor PACE - Misplaced Pages Continue

2432-402: The address was constructed as normal, adding the eight address bits to the base page or PC. It would then read the 16-bit value in that memory location and then load or store from that address. When combined with the X flag, the 8-bit offset is first added or subtracted from the indicated index register. Another user of indirect addressing was ISZ and DSZ . These incremented or decremented

2508-417: The addressing mode. The remaining eight bits in the instruction normally held an 8-bit address. This meant that an arbitrary memory location could not be specified directly; several different systems were used to build the required 16-bit address from the 8-bit value. There were 43 instructions and 45 opcodes, with two opcodes each for LD and ST (see below). When X was zero, the address bits represented

2584-1292: 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

2660-574: The bits in the SCF are mostly mapped directly onto pins on the outside of the chip. Bits 1 through 5 are the IE1 through IE5 flags, which are used to control interrupts in a priority fashion. IE1 is set only in the case of a stack overflow/underflow. The other four can be used to disable individual interrupt lines, or more commonly, produce a binary value from 0 to 15 that external devices use to determine whether or not they should perform an interrupt. For instance, if

2736-445: The bus, which it might do by mapping 128 bytes of internal buffer onto the split base page mentioned earlier. In contrast to most microcomputer designs of the era, the PACE did not use variable-length instructions, all instructions used 16 bits. The 16-bit words were broken into a series of bit fields for the instruction format. The top six bits, 10 through 15, held the opcode , while bits 8 (R for Relative) and 9 (X for indeX) indicated

2812-458: 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

2888-494: The chip area. The polysilicon gate material not only made the self-aligned gate possible, it also resulted in a reduced threshold voltage and consequently in a lower minimum power supply voltage (e.g. -16 V ), reducing the power consumption. Because of the lower power supply voltage, silicon gate PMOS logic is often referred to as low-voltage PMOS in contrast to the older, metal-gate PMOS as high-voltage PMOS . For various reasons Fairchild Semiconductor did not proceed with

2964-472: 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

3040-489: 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

3116-403: The development of PMOS integrated circuits as intensively as the involved managers wanted. Two of them, Gordon Moore and Robert Noyce , decided in 1968 to found their own startup instead – Intel . They were shortly afterwards joined by other Fairchild engineers, including Federico Faggin and Les Vadasz . Intel introduced its first PMOS static random-access memory with a capacity of 256 bit,

National Semiconductor PACE - Misplaced Pages Continue

3192-485: 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

3268-554: The external devices, like the main memory , to latch the address between cycles. National Semiconductor's IMP-16 had been inspired by the Data General Nova but had a number of minor differences in its ISA. Among these was the handling of the four user-accessible 16-bit processor registers . In the Nova, the first two registers were general-purpose accumulators and used for most basic arithmetic and logic operations, while

3344-469: The first 4-bit microprocessor (4004), the first 8-bit microprocessor (8008), the first single-chip 16-bit microprocessor (PACE), and the first single-chip 4-bit microcontroller (TMS1000; RAM and ROM on the same chip as the CPU ). By 1972, NMOS technology had finally been developed to the point where it could be used in commercial products. Both Intel (with the 2102) and IBM introduced 1 kbit memory chips. As

3420-432: The first working MOSFET at Bell Labs in 1959. They fabricated both PMOS and NMOS devices but only the PMOS devices were working. It would be more than a decade before contaminants in the manufacturing process (particularly sodium) could be managed well enough to manufacture practical NMOS devices. Compared to the bipolar junction transistor , the only other device available at the time for use in an integrated circuit ,

3496-519: The introduction of the NMOS logic concept, or nMOS. This type of logic has the significant advantage that its internal transistors do not require a large voltage on the substrate layer, like pMOS. In practical terms, this means an nMOS processor can operate with only two input voltages rather than three, and the positive supply can be set to +5V, making interfacing with TTL circuits trivially easy. National Semiconductor took advantage of this technique with

3572-402: The last instruction in the loop would be a JMP back to the top of the loop, but when the value reached 0 it would automatically SK past that JMP and continue. This style of looping control is common in minicomputers, but not so in microcomputer designs. In dedicated micros, this sort of operation is normally accomplished with several instructions, one that compares the loop index with

3648-649: 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

3724-612: The main technology for microprocessors. PMOS circuits have a number of disadvantages compared to the NMOS and CMOS alternatives, including the need for several different supply voltages (both positive and negative), high-power dissipation in the conducting state, and relatively large features. Also, the overall switching speed is lower. PMOS uses p-channel (+) metal-oxide-semiconductor field effect transistors (MOSFETs) to implement logic gates and other digital circuits . PMOS transistors operate by creating an inversion layer in an n-type transistor body. This inversion layer, called

3800-401: 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 a teleprinter and at least four thousand words of memory, that

3876-423: 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

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3952-533: 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

4028-496: 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

4104-547: 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

4180-454: The p-channel, can conduct holes between p-type "source" and "drain" terminals. The p-channel is created by applying a negative voltage (-25V was common ) to the third terminal, called the gate. Like other MOSFETs, PMOS transistors have four modes of operation: cut-off (or subthreshold), triode, saturation (sometimes called active), and velocity saturation. While PMOS logic is easy to design and manufacture (a MOSFET can be made to operate as

4256-411: The process but also increases static power dissipation. Additionally, the asymmetric input logic levels make PMOS circuits susceptible to noise. Most PMOS integrated circuits require a power supply of 17-24 volt DC. The Intel 4004 PMOS microprocessor, however, uses PMOS logic with polysilicon rather than metal gates allowing a smaller voltage differential. For compatibility with TTL signals,

4332-515: The reliability of PMOS circuits at the time and ultimately led to the demise of General Microelectronics. Other companies continued to manufacture PMOS circuits such as large shift registers ( General Instrument ) or the analogue multiplexer 3705 ( Fairchild Semiconductor ) which were not feasible in bipolar technologies of the day. A major improvement came with the introduction of polysilicon self-aligned gate technology in 1968. Tom Klein and Federico Faggin at Fairchild Semiconductor improved

4408-427: The same address in both locations so they would always call the same code, which would then determine what had actually occurred. There were similar problems when a level-0 interrupt occurred within a 12 cycles of other interrupts, causing the wrong code to be called. All of these problems were solved in the 8900. Although the PACE ran at a relatively fast clock speed for the era, the instruction set architecture (ISA)

4484-449: 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

4560-415: The second two could be used as operands or used as index registers . The IMP-16 followed this model, but the PACE changed a number of instructions so that they operated only on the first accumulator, AC0. The original Nova did not implement a stack in hardware, although this was added in the later Nova 3 models starting in 1975. PACE implemented a different style of stack using a hidden stack pointer which

4636-406: The self-aligned gate process to make it commercially viable, resulting in the release of the analogue multiplexer 3708 as the first silicon-gate integrated circuit. The self-aligned gate process allowed tighter manufacturing tolerances and thus both smaller MOSFETs and reduced, consistent gate capacitances. For instance, for PMOS memories this technology delivered three to five times the speed in half

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4712-485: The setting of the BPS , instead most systems connected the pin to one of the status pins, and then used the status changing instructions to control it. Indirect addressing in the PACE was limited, supported primarily by the LD and ST instructions, which load and saved values between the registers and memory. Indicating indirect addressing used separate opcodes, as opposed to using the addressing indication bits. When used,

4788-471: 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 ,

4864-543: 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

4940-403: 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

5016-407: The transistors provide low resistance, and the capacitive charge at the output accumulates very quickly (similar to charging a capacitor through a very low resistance). But the resistance between the output and the negative supply rail is much greater, so the high-to-low transition takes longer (similar to discharge of a capacitor through a high resistance). Using a resistor of lower value will speed up

5092-417: 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"

5168-505: 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

5244-403: The value in these flags adds up to 5, any device with an interrupt value of 5 or lower (1 is the highest priority) can express it, a device wishing to call a lower priority, say 7, is being instructed to hold it. Similarly, SCF flags F11 through F14 are used as outputs to provide direct control over external devices. For instance, they might be used to indicate that device 6 should present data on

5320-471: 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,

5396-490: 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

5472-432: Was also 16-bits wide. Bits 0 and 15 are both set to 1 and are normally unused, while the remaining fourteen are actively used. This included common flags like CRY to indicate an addition resulted in a carry, OVF if it overflowed, and LINK, which indicated a bit needed to be shifted during shift and rotate instructions. LINK is normally handled using the carry flag in most microcomputer CPU designs, but having two separate flags

5548-440: Was implemented using microcode and the multiplexed bus required two cycles for each memory access. As a result, a typical instruction took about 12 to 30 microseconds to complete, making it about the same speed as contemporary 8-bit processors like the Intel 8080 . This still provided an advantage when working with larger data, for instance in a floating point library, as that single instruction could process twice as much data in

5624-541: 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

5700-417: 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

5776-517: Was that the various signal pins now worked at TTL voltages, allowing them to communicate directly with external systems like memory. This change did not address the issue of having to latch the address on the shared data/address bus, but it did make such latching much easier. Instead of requiring the relatively complex BTE chip, this task could now be performed by common TTL components, although National Semiconductor suggested their own INS8208 and INS8212 for this purpose. The bus could now be implemented by

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