PDP-11

LSI-11PDP-11/70DEC PDP-11PDP-11/45PDP-11/40DEC LSI-11PDP11PDP-11/20DEC PDP-11/70MINC-11
The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a succession of products in the PDP series.wikipedia
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Digital Equipment Corporation

DECDigitalDigital Equipment
The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a succession of products in the PDP series.
Looking to simplify and update their line, DEC replaced most of their smaller machines with the PDP-11 in 1970, eventually selling over 600,000 units and cementing DEC's position in the industry.

16-bit

16 bit16-16
The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a succession of products in the PDP series.
undefined 1965–70) include the IBM 1130, the HP 2100, the Data General Nova, and the DEC PDP-11.

Unibus

Additionally, the innovative Unibus system allowed external devices to be easily interfaced to the system using direct memory access, opening the system to a wide variety of peripherals. Early models of the PDP-11 had no dedicated bus for input/output, but only a system bus called the Unibus, as input and output devices were mapped to memory addresses.
The Unibus was the earliest of several computer bus and backplane designs used with PDP-11 and early VAX systems manufactured by the Digital Equipment Corporation (DEC) of Maynard, Massachusetts.

Motorola 68000

68000M68000MC68000
The design of the PDP-11 inspired the design of late-1970s microprocessors including the Intel x86 and the Motorola 68000.
The MACSS team drew heavily on the influence of minicomputer processor design, such as the PDP-11 and VAX systems, which were similarly microcode-based.

MS-DOS

DOSMS-DOS 5.0MS-DOS 6.0
Design features of PDP-11 operating systems, as well as other operating systems from Digital Equipment, influenced the design of other operating systems such as CP/M and hence also MS-DOS.
The company planned, over time, to improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS, which would also run on the Motorola 68000, Zilog Z8000, and the LSI-11; they would be upwardly compatible with Xenix, which Byte in 1983 described as "the multi-user MS-DOS of the future".

CP/M

CP/M-80CP/M operating systemBDOS
Design features of PDP-11 operating systems, as well as other operating systems from Digital Equipment, influenced the design of other operating systems such as CP/M and hence also MS-DOS.
CP/M's command-line interface was patterned after the operating systems from Digital Equipment, such as RT-11 for the PDP-11 and OS/8 for the PDP-8.

Data General

Data General Corporation Data General CorporationDG.com
Several of the engineers from the PDP-X left DEC and formed Data General.
It lacked general registers and the stack-pointer functionality of the more advanced PDP-11, as did competing products, such as the HP 1000; compilers used hardware-based memory locations in lieu of a stack pointer.

VAX-11

VAX-11/780VAX-11/750VAX 11/780
An effort to expand the PDP-11 from 16 to 32-bit addressing led to the VAX-11 design, which took part of its name from the PDP-11.
The VAX-11 is a discontinued family of minicomputers developed and manufactured by Digital Equipment Corporation (DEC) using processors implementing the VAX instruction set architecture (ISA), succeeding the PDP-11.

DEC J-11

J-11DEC J11
A two-or-three-chip processor, the J-11 was developed in 1979.
The J-11 is a microprocessor chip set that implements the PDP-11 instruction set architecture (ISA) jointly developed by Digital Equipment Corporation and Harris Semiconductor.

Unix

UNIX operating systemAT&T UnixUnix-like
The first officially named version of Unix ran on the PDP-11/20 in 1970.
Version 4 Unix, however, still had many PDP-11 dependent codes, and was not suitable for porting.

PDP-11 architecture

PDP-11DEC PDP-11EIS instructions
The article on PDP-11 architecture provides more details on interrupts.
It is implemented by central processing units (CPUs) and microprocessors used in PDP-11 minicomputers.

C (programming language)

CC programming languageC language
It is commonly stated that the C programming language took advantage of several low-level PDP-11–dependent programming features, albeit not originally by design.
Eventually, they decided to port the operating system to a PDP-11.

VAX

DEC VAXVAX 11/780DEC VAX ULTRIX
DEC's 32-bit successor to the PDP-11, the VAX (for "Virtual Address eXtension") overcame the 16-bit limitation, but was initially a superminicomputer aimed at the high-end time-sharing market.
A 32-bit system with a complex instruction set computer (CISC) architecture based on DEC's earlier PDP-11, VAX ("virtual address extension") was designed to extend or replace DEC's various Programmed Data Processor (PDP) ISAs.

Word (computer architecture)

wordwordsword size
During this period, the computer market was moving from computer word lengths based on units of 6 bits to units of 8 bits, following the introduction of the 7-bit ASCII standard.
In the mid-1970s, DEC designed the VAX to be a 32-bit successor of the 16-bit PDP-11.

Western Digital

WDWestern Digital CorporationParadise
The LSI-11 (PDP-11/03), introduced in February 1975 is the first PDP-11 model produced using large-scale integration; the entire CPU is contained on four LSI chips made by Western Digital (the MCP-1600 chip set; a fifth chip can be added to extend the instruction set, as pictured on the right).
The MCP-1600 was used to implement DEC's LSI-11 system and their own Pascal MicroEngine microcomputer which ran the UCSD p-System Version III and UCSD Pascal.

System bus

dual independent busbusavionics data bus
Early models of the PDP-11 had no dedicated bus for input/output, but only a system bus called the Unibus, as input and output devices were mapped to memory addresses.
This was implemented in the Unibus of the PDP-11 around 1969, eliminating the need for a separate I/O bus.

Central processing unit

CPUprocessorprocessors
Instead, memory was interfaced by dedicated circuitry and space in the CPU cabinet, while the Unibus continued to be used for I/O only.
DEC's PDP-8/I and KI10 PDP-10 also switched from the individual transistors used by the PDP-8 and PDP-10 to SSI ICs, and their extremely popular PDP-11 line was originally built with SSI ICs but was eventually implemented with LSI components once these became practical.

DEC Professional (computer)

DEC ProfessionalPro-350PRO-380
A line of personal computers based on the PDP-11, the DEC Professional series, failed commercially, along with other non-PDP-11 PC offerings from DEC.
The Professional 325 (PRO-325) and Professional 350 (PRO-350) were PDP-11 compatible microcomputers introduced in 1982 by Digital Equipment Corporation (DEC) as high-end competitors to the IBM PC.

Programmed Data Processor

PDPProgrammable Data ProcessorPDP-16
The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a succession of products in the PDP series.

Booting

bootloaderboot loaderboot
The operator can also specify which disk to boot from.
Other minicomputers with such simple form of booting include Hewlett-Packard's HP 2100 series (mid-1960s), the original Data General Nova (1969), and DEC's PDP-11 (1970).

Amiga

Commodore AmigaAmiga ComputerAmiga 500/600 (OCS/ECS)
Personal computers based on the 68000 like the Apple Lisa and Macintosh or the Commodore Amiga arguably constituted less of a threat to DEC's business, although technically these systems could also run Unix derivatives.
TRIPOS was a multitasking system that had been written in BCPL during the 1970s for minicomputer systems like the PDP-11, but later experimentally ported to the 68000.

Bus (computing)

buscomputer busdata bus
Early models of the PDP-11 had no dedicated bus for input/output, but only a system bus called the Unibus, as input and output devices were mapped to memory addresses.
This was implemented in the Unibus of the PDP-11 around 1969.

X86

x86 architectureIntel x8680x86
The design of the PDP-11 inspired the design of late-1970s microprocessors including the Intel x86 and the Motorola 68000.
Some minicomputers like the PDP-11 used complex bank-switching schemes, or, in the case of Digital's VAX, redesigned much more expensive processors which could directly handle 32-bit addressing and data.

Xenix

SCO XenixMS-XenixTrusted Xenix
In the early years, in particular, Microsoft's Xenix was ported to systems like the TRS-80 Model 16 (with up to 1 MB of memory) in 1983, and to the Apple Lisa, with up to 2 MB of installed RAM, in 1984.
In 1981, Microsoft said the first version of XENIX was "very close to the original UNIX version 7 source" on the PDP-11, and later versions were to incorporate its own fixes and improvements.

Mentec PDP-11

M100 and family from MentecMentecMentec M100
Mentec Computer Systems Limited was a subsidiary of Mentec Limited that developed PDP-11 processors.