DEC Mini Computers - PDP Family

How it all began

In 1957, Kenneth Olsen and Harlan Anderson established Digital Equipment Corporation (DEC), which launched its first PDP-1 computer. Prior to that, Olsen and Anderson participated in the development of the AN / FSQ-7, TX-0 and TX-2 machines at Lincoln Labs.


AN / FSQ-7


Tx-0


Tx-2
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The company expanded, developed and due to the fact that the cost of such mini-computers was relatively not high (PDP-1 cost 120 thousand dollars, while mainframes, mainframes cost more than a million dollars), quickly found its customers and occupied a new niche on the market. DEC provided the market with small and inexpensive computers as an alternative to IBM mainframes. Subsequently, 16 models of the PDP family of computers were released. Each subsequent upgrade of the PDP increased the performance of the computer, the range of peripheral devices was expanded.

The PDP-1 was a 4K computer with 18 bit words. Computer speed - 200 thousand teams per second. Its cost was less than 5% of the cost of IBM 7094. Initially, the PDP-1 computer was used for teaching students. Glory to the PDP-1 came soon: the US Congress chose this compact computer as a typical computing platform that was used in mobile seismic stations for monitoring nuclear tests. Orders from NASA and other commercial organizations began to arrive. Began its mass production, he was "baptized" - Programmed Data Processor (PDP).

The PDP-1 machine reader was built on photocells and its speed reached 400 characters per second, which was a great advantage over the Flexowriter used at that time, which performance was only 10 characters per second.


Flexowriter

The principle of operation of the flexorayter was simple: the engineer typed the text as on an ordinary typewriter, the flexorayter printed it on paper and made holes in the punched tape, after which the punched tape was used to enter data into the computer.

The machine was equipped with a display station, which was monochrome with a CRT display, with a diameter of 16 inches with a resolution of 1024 x 1024 pixels (the number of points that can be set as the boundary coordinates of the displayed segments).


PDP-1





One copy was presented to students of MIT (Massachusetts Institute of Technology). Student Stephen Peiner wrote one of the world's first text editing software for the PDP-1. A total of 50 PDP-1s were released, the second PDP-2 model was not launched into serial production, but only a prototype was created.

The PDP-3 was developed by order of the government (presumably the CIA) in a single copy.

The next model of the PDP family, the PDP-4 , was in many ways similar to the PDP-1, which was released in 1962. It is important to note that the software compatibility between the machines was not yet there.


PDP-4

The cost of the PDP-4 was two times cheaper (about 65 thousand dollars), but it was sold much worse than its successful predecessor, the reason was the lack of a developed software and technology base. It was used in laboratory studies for data processing. The PDP-4 was a unicast parallel-acting machine with a binary number system. Although the PDP-4 was originally conceived as a 12-bit computer, the 18-bit option was chosen at the last moment.



At the request of the Atomic Energy Commission in 1963, the PDP-5 was developed to control nuclear reactors. This model was used with the PDP-4 machine, which was the main control computer. Later, the PDP-5 mini-computer became the predecessor of the PDP-8. The cost of such a machine was only 27 thousand dollars, for all the time 1000 copies were produced. It was a 12-bit machine, with 4K word of RAM and a simple but powerful instruction set. The memory access cycle was 6 microseconds.


PDP-5

The PDP-5 was a unicast parallel action 12-bit computer with a binary number system.

At the end of 1964, the first machine created on the basis of multiprocessor technology appeared on the market - the PDP-6 . Basically, the machine was used for data processing, a total of about 20 copies were produced. At that time it was a “revolutionary” computer.


It was the first machine with the concept of "time-sharing" (time-shared), which allowed many users to simultaneously interact with one computer. This system gives each user some processor time to complete the task. It was a 36-bit machine, the memory access cycle was 2 microseconds. The cost of such a mini-computer was approximately 300 thousand dollars.


PDP-6

In 1965, the PDP-7 was created for real-time systems. The cost of such an 18-bit mini-computer was 72 thousand dollars, a total of 120 copies were produced. The PDP-7 machine is known for developing the operating system, which was later transferred to the PDP-11. The well-known Unix operating system (its first version) was created specifically for the PDP-7. PDP-7 in its performance in no way inferior to the giants of IBM, and the size was several times smaller. The OS was written in assembler and was tied to the PDP-7 architecture.


PDP-7

The memory access cycle was 1.75 microseconds, while the addition operation was 4 microseconds. The mini-computer was equipped with a keyboard, printer, and a DECtape tape drive.

Soon an order came from a Canadian energy company to build a machine for controlling a nuclear reactor. It was decided to design a universal machine. So in 1965, the PDP-8 appeared - the first car of the PDP-8 family, it became the first mass production machine in the world and the most successful development of the DEC company. The cost of the car was 18 thousand dollars, the price was later reduced.



The first PDP-8 was a 12-bit mini-computer with 4 KB RAM, with the ability to expand it to 48 KB, the access time to memory was 1.2 μs. The base RAM was 4,096 12-bit words, which were paginated with 128 words each. The performance of the machine was 385 thousand additions per second, the subtraction operation took 5 μs, multiplying two signed 12-bit numbers, giving a 24-bit result, - 256.5 μs., While dividing - 342.4 μs. To increase speed during multiplication / division operations, an optional arithmetic accelerator board (Extended Arithmetic Element) has been developed.



The software included such procedural programming languages ​​(HLM) of a high level: Fortran (two versions), FOCAL, DIBOL, various macro assemblers, BASIC, utilities, debuggers, single-task OS.

Over a thousand programs have been written under the PDP-8 family, more than 60 peripheral devices have been developed, among them magnetic disks, tapes. It was possible to connect IBM tape drives, 17 types of teletypes, graphic displays, devices for reading tape and output to punched tape. It is important that PDP-8 cards have been developed for input and output of analog signals, which made it possible to use it as part of laboratory equipment.

For 15 years, the following PDP-8 models have been developed: LINC-8, PDP-8 / S, PDP-8 / I, PDP-8 / L, PDP-12, PDP-8 / E - 8 / E, PDP- 8 / F, PDP-8 / M, PDP-8 / A, PDP-8 compliant single-chip Intersil 6100 microprocessor for the VT78 terminal, PDP-8-compatible single-chip Harris 6120 microprocessor.


PDP-8 / I


PDP-8 / E front panel

Established in 1966, the PDP-9 is considered an upgrade of the PDP-7, such 18-bit machines were released in an amount of 445 pieces, the price was $ 35 thousand per unit.


PDP-9

In 1969, the PDP-10 was created on the basis of the PDP-6. It was released under the name DECSYSTEM-20, and was a 36 bit mini-computer. At that time, the machine provided more opportunities for programming in assembler, had a large set of commands for executing commands, for performing operations with individual bits, for working with fields and integers.


PDP-10

In 1970, the PDP-11 was developed. It was a series of 16-bit mini-computers. They were an alternative to 12-bit and 16-bit computers, the innovative solution was an 18-bit UNIBUS internal bus, a set of registers and an addressing system. The bus architecture allowed other companies to set up standard peripherals for the PDP-11. In the PDP-11, instead of individual buses, there is one common information channel for each peripheral device. It is called the common bus and is the core of the PDP-11 system.


PDP-11 processor

The first model of this family was the PDP 11/20 computer. According to various sources, a total of 16 to 22 different models were produced. The “family tree” of the PDP-11 is confusing and complicated.

16-bit PDP-11/20 with a KA11 processor, which later evolved from a small DEC TTL-module M Series Integrated Circuit FLIP-CHIP Modules. Onboard 8 general-purpose registers and the UNIBUS bus, which linked all the components of the system, - CPU, memory, peripherals (the UNIBUS bus was not the successor of the OMNIBUS from the PDP-8). The bus was 18-bit, but only 16 were actually used, addressing the memory to a maximum of 32 K words. The original OS was DOS / BATCH. Later, a cheaper version of the PDP-11/20, the PDP-11/05, was developed.


PDP-11/20

D 1973 PDP-11/40 was released, possessed 18-bit MMU, FPU and EIS / FIS (extended / floating point instruction set). Under it was developed a graphic workstation GT44. 11/40 machines were often used in DECsystem-10 (KL10) as input / output processors. OS for PDP-11/40 - DOS / BATCH, RSX11, RT-11 and RSTS.

In 1975, the next PDP-11/03 machine was developed, using LSI semiconductor technology (LSI-11, LSI-11/2) processors. PDP-11/03 was used as a preprocessor for the VAX11-780. This model was with the lowest performance in comparison with its "brothers".


LSI11 (PDP11 / 03)

In the spring of 1975, the largest minicomputer of the PDP-11/70 line, with the KB11B processor, which contained the cache memory (2 KB of bipolar memory), was released. It was released about 10 thousand copies.


PDP-11/70


PDP-11/34


PDP 11/55

PDP-11 series models

The PDP-11 was an incredible success, in the USSR the KM1801VM2 processor (analogue of DEC LSI-11/03) was “completely copied” and on its basis almost complete PDP-11 clones were built - the DVK and a series of microcomputers, such as BK-0010, UKSC and MK-90 "... Variations on the theme of PDP-11 took root in our country under two names: SM-COMPUTER and" Electronics ".

In 1969, the PDP-12 was developed; 725 of these machines were produced, they were sold for $ 27,900. It was a dual-processor 12-bit mini-computer. The main operating system on the PDP-12 was the LAP6-DIAL (Display Interactive Assembly Language), later it was supplanted by one of the versions of the OS / 8 operating system (OS / 12).


PDP-12

The PDP-14 was a 1-bit machine, a programmable controller. It consisted of a control unit and several systems located in a stand-alone external cabinet.



The PDP-15 was released in 1970. This was the last 18-bit system from DEC. Previous models of PDP were based on discrete transistors, and PDP-15 - on integrated TTL chips. The PDP-15 was compatible with the PDP-9 and included some additional features, such as memory protection and floating point operations.


PDP-15

In 1972, the PDP-16 was developed, for all time only 3 copies of such a specialized modular system were released.



Corporation Digital Equipment and its PDP mini-computers have rightfully entered the history of the IT market, becoming a legend.