Megabyte was used to describe the 22-bit addressing of DEC PDP-11 / 70 ( 1975 )

The effort was sufficiently complete that during the summer of 1973 the Unix kernel for the PDP-11 was rewritten in C. During the 1972 – 73 period there was a need to port to Honeywell 635 and IBM 360 / 370 machines, so Mike Lesk wrote the " portable I / O package " which would become the C " standard I / O " routines.

Many more machines offered user-programmable writable control stores as an option ( including the HP 2100, DEC PDP-11 / 60 and Varian Data Machines V-70 series minicomputers ).

Implementations also exist for the Interdata 8 / 32, PDP-11, VAX, Alpha platforms and HP Integrity servers ; for the Honeywell, and for the Computer Technology Limited ( CTL, later ITL ) Modular-1 ; as well as for SPARC running Solaris and Intel running Linux.

* PDP-11 CORAL / ASM interfacing library

Examples of CISC instruction set architectures are System / 360 through z / Architecture, PDP-11, VAX, Motorola 68k, and x86.

Digital Equipment Corporation should not be confused with the unrelated companies Digital Research, Inc or Western Digital ( despite the latter manufacturing the LSI-11 chipsets used in DEC's low end PDP-11 / 03 computers ).

The PDP-11 supported several operating systems, including Bell Labs ' new Unix operating system as well as DEC's DOS-11, RSX-11, IAS, RT-11, DSM-11, and RSTS / E.

Large numbers of PDP-11 / 70s were deployed in telecommunications and industrial control applications.

ed was originally written in PDP-11 / 20 assembler by Ken Thompson in 1971.

The most significant were Digital Equipment Corporation with DSM ( Digital Standard MUMPS ), InterSystems with ISM ( InterSystems M ) on VMS and UNIX, and M / 11 + on the PDP-11 platform.

* The Digital Equipment Corporation PDP-11 processors, with the exception of the PDP-11 / 20, were microprogrammed.

KL10 frontend PDP-11 / 40

The KL class machines could not be started without the assist of a PDP-11 / 40 frontend computer installed in every system.

PDP-11 / 40

Design features of the PDP-11 influenced the design of microprocessors such as the Motorola 68000 ; design features of its 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 first officially named version of Unix ran on the PDP-11 / 20 in 1970.

PDP-11 / 40 with TU56 dual DECtape drive.

The last models of the PDP-11 line were the PDP-11 / 94 and-11 / 93 introduced in 1990.

* PDP-11 / 03 ( also known as the LSI-11 / 03 ) — The first LSI PDP-11, this system used a chipset from Western Digital and supported 60 kB of memory.

* PDP-11 / 68 — A follow-on to the PDP-11 / 60 that would have supported 4 MB of physical memory.

The Digital Editing System, as Soundstream called it, consisted of a DEC PDP-11 / 60 minicomputer running a custom software package called DAP ( Digital Audio Processor ), a Braegen 14 "- platter hard disk drive, a storage oscilloscope to display audio waveforms to be edited, a video display terminal for controlling the system, and interface cards that plugged into the PDP-11's Unibus slots ( the Digital Audio Interface, or DAI ) that provided analog and digital audio input and output for interfacing to both Soundstream's digital recorders and conventional analog tape recorders as well.

Other versions of Runoff were developed for various computer systems including Digital Equipment Corporation's PDP-11 minicomputer systems running RT-11, RSTS / E, RSX on Digital's PDP-10 and for OpenVMS on VAX minicomputers, as well as Sperry Unisys Univac 90 / 60 mainframe using the EDT text editor under the VS / 9 operating system.

* PDP-11 / 20 and PDP-11 / 15 — The original, non-microprogrammed processor ; designed by Jim O ' Loughlin.

* PDP-11 / 35 and PDP-11 / 40 — A microprogrammed successor to the PDP-11 / 20 ; the design team was led by Jim O ' Loughlin.

* PDP-11 / 45, PDP-11 / 50, and PDP-11 / 55 — A much faster microprogrammed processor that could use up to 256 kB of semiconductor memory instead of or in addition to core memory.

* PDP-11 / 70 — The 11 / 45 architecture expanded to allow 4 MB of physical memory segregated onto a private memory bus, 2 kB of cache memory, and much faster I / O devices connected via the Massbus.

* PDP-11 / 05 and PDP-11 / 10 — A cost-reduced successor to the PDP-11 / 20.

* PDP-11 / 34 and PDP-11 / 04 — Cost-reduced follow-on products to the 11 / 35 and 11 / 05 ; the PDP-11 / 34 concept was created by Bob Armstrong.

* PDP-11 / 44 — Replacement for the 11 / 45 and 11 / 70 that supported optional cache memory and floating-point processor, and included a sophisticated serial console interface and support for 4 MB of physical memory.

* PDP-11 / 24 — First VLSI PDP-11 for Unibus, using the " Fonz-11 " ( F11 ) chip set with a Unibus adapter.

* PDP-11 / 84 — Using the VLSI " Jaws-11 " ( J11 ) chip set with a Unibus adapter.

* PDP-11 / 94 — J11-based, faster than 11 / 84.

* PDP-11 / 23 — Second generation of LSI ( F-11 ).

An early version of yacc was produced with this PDP-11 configuration.

DEC would later introduce the extremely popular PDP-11 line that originally was built with SSI ICs but was eventually implemented with LSI components once these became practical.

In stark contrast with its SSI and MSI predecessors, the first LSI implementation of the PDP-11 contained a CPU composed of only four LSI integrated circuits.

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 DECs position in the industry.

MUMPS was developed with the support of a government research grant, and so MUMPS was released to the public domain ( no longer a requirement for grants ), and was soon ported to a number of other systems including the popular DEC PDP-8, the Data General Nova and the DEC PDP-11 and the Artronix PC12 minicomputer.

Some platforms with a power-of-two word size still have instruction subwords that are more easily understood if displayed in octal ; this includes the PDP-11 and Motorola 68000 family.

While many attributed the success of the PDP-11 to DEC's decision to make the PDP-11 Unibus an open architecture, DEC reverted to prior philosophy with the KL, making MASSbus both unique and proprietary.

The PDP-10 was eventually eclipsed by the VAX superminicomputer machines ( descendants of the PDP-11 ) when DEC recognized that the PDP-10 and VAX product lines were competing with each other and decided to concentrate its software development effort on the more profitable VAX.

The 16-bit PDP-11 instruction set has been very influential, with processors ranging from the Motorola 68000 to the Renesas H8 and Texas Instruments MSP430, inspired by its highly orthogonal, general-register oriented instruction set and rich addressing modes.

The PDP-11 had several uniquely innovative features, and was easier to program than its predecessors with its use of general registers.

Higher-performance members of the PDP-11 family, starting with the PDP-11 / 45 Unibus and 11 / 83 Q-bus systems, departed from the single-bus approach.

In the PDP-11 / 70, this was taken a step further, with the addition of a dedicated interface between disks and tapes and memory, via the Massbus.

Later PDP-11 Unibus systems were designed to use similar Q-Bus processor cards, using a Unibus adapter to support existing Unibus peripherals, sometimes with a special memory bus for improved speed.

The early VAXes provided a PDP-11 compatibility mode under which much existing software could be immediately used, in parallel with newer 32-bit software.

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.

later PDP-11 / 70 with disks and tape