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.

The LSI-11 ( PDP-11 / 03 ), introduced in February, 1975 was the first PDP-11 model produced using large-scale integration ; the entire CPU was contained on four LSI chips made by Western Digital ( the MCP-1600 chip set ; a fifth chip could be added to extend the instruction set, as pictured on the right ).

For example, a system variant of the PDP-11 / 03 introduced full system Power-On Self-Test ( POST ).

Digital produced a version of the PDP-11 / 03 called the MINC-11, housed in a portable cart, and equipable with Digital-designed laboratory I / O modules supporting capabilities such as analog input and output.

Historically, RT-11 also served as the inspiration for many microcomputer OS's, as these were generally being written by programmers who cut their teeth on one of the many PDP-11 models.

* RSX-11M-Plus — a much extended version of RSX-11M, originally designed to support the multi-processor PDP-11 / 74, a computer that was never released, but also used widely as a standard operating system on the PDP-11 / 70.

The introduction of memory management in the newer PDP-11 computers not only meant these machines were able to address four ( 4 ) times the amount of memory ( 18bit addressing, 256K bytes ), it also paved the way for the developers to separate user mode processes from the core of the kernel.

MOS was also used in high-end PDP-11 clones.

The original version, DIBOL-8, was produced for PDP-8, PDP-11 and DIBOL-32 VAX / VMS systems, though it can also be run on other systems through emulators.

Other DEC operating systems also had PTYs, including RSTS / E for the PDP-11, as did the third-party TENEX operating system for the PDP-10.

A PDP-11 implementation ( the PDP-11 / 27 ) was also envisioned but never advanced beyond the concept stage.

All other I / O devices in the PRO family were also different ( in most cases, radically different ) from their counterparts on other PDP-11 models.

The V7m product was later renamed to Ultrix-11 to establish the family with Ultrix-32, but as the PDP-11 faded from view Ultrix-32 became known simply as Ultrix.

; PDP-11: The archetypal minicomputer ; a 16-bit machine and another commercial success for DEC. ( Also the LSI-11, primarily for embedded systems ).

In 1994 DEC sold the PDP-11 system-software rights to Mentec Inc., an Irish producer of LSI-11 based boards for Q-Bus and ISA architecture personal computers, and in 1997 discontinued PDP-11 production.

# Redirect PDP-11 # LSI-11

* LSI-11, an early large-scale integration computer processor that implemented the DEC PDP-11 instruction set

TSX-Plus is a multi-user operating system for the PDP-11 / LSI-11 series of computers.

Due to the constraints of the memory management system in the PDP-11 / LSI-11, the entire operating system core must occupy no more than 40 kibibytes of memory, out of a maximum possible 4 mebibytes of physical memory that can actually be installed in those machines ( mandated by the 22-bit address space ).

It was binary compatible with Unix V6 on PDP-11, but it could run on non-memory managed systems ( like LSI-11 or PDP-11 / 23 ) as well.

The PRO-325 and-350 used the F-11 chipset ( as used in LSI-11 / 23 systems ) to create a relatively compact single-board PDP-11 with up to 6 expansion slots of proprietary CTI ( Computing Terminal Interconnect ) bus using 90-pin ZIF connectors.

Bell Labs developed several variants of V6, including the stripped-down MINI-UNIX for low-end PDP-11 models, LSI-UNIX or LSX for the LSI-11, and the real-time operating system UNIX / RT, which merged V6 Unix and the earlier MERT hypervisor.

In its final incarnation, Belle was composed of a PDP-11 / 23 with a LSI-11 processor, and many custom boards.