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The PDP-11 is a series of computers introduced in 1969 [1] by Digital Equipment Corporation (DEC); it was in production at DEC from 1970-1990, after which the line was sold to Mentec, who produced a few newer models.

A loaded QBUS PDP-11/23 PLUS

The machine word size was 16 bits, and it was a general register architecture. (For more information about the architecture, see PDP-11 architecture.)

PDP-11's came in two groups: those which used the UNIBUS for a bus, and the later ones which used the QBUS. Eventually DEC stopped producing UNIBUS PDP-11's (the last were the PDP-11/44 and PDP-11/24); later 'UNIBUS' machines (the PDP-11/84 and PDP-11/94) actually contained QBUS processors with a QBUS<->UNIBUS adapter board.

It could run a variety of operating systems. Many were produced by DEC themselves, but several were produced by third-parties. Often DEC would purchase or rebrand this OS and resell it as their own product. For example, UNIX sold as Ultrix by DEC.

Operating Systems

Unix based Operating Systems

These are the original Bell Laboratories releases of Unix.

This was the first shipping unix distro by AT&T. It only supported the PDP-11 and VAX computers.

This version was a port of the 4.3 feature set to the PDP-11. Although considered impossible by many, it accomplished this by using overlays for portions of the kernel, and to allow for user programs larger then 64kb.

This version is still supported, and if one really felt the need to load a Unix for use on a PDP-11 this would be the best fit. It has support for TCP/IP, large memory space and is the best UNIX experence one can get going to get on a 16-bit mini.

Other OS's

PDP-11 Models and notes

Model Introduced Bus Type Addressing Notes Speed (VUPS)
11/20 1969[1] UNIBUS 16-bit
11/05 1972 UNIBUS 16-bit
11/10 1972 UNIBUS 16-bit KD11-B processor[*]
11/15 1972 UNIBUS 16-bit OEM model
11/40 1973 UNIBUS 18-bit
11/45 1973 UNIBUS 18-bit core memory
11/50 1975 UNIBUS 18-bit MOS memory
11/70 1975 UNIBUS 22-bit 0.6
11/03 1975 QBUS 16-bit first QBUS model, first F-11 0.5
11/34 1976 UNIBUS 18-bit 0.21
11/04 1976 UNIBUS 16-bit 0.11
11/55 1976 UNIBUS 18-bit fast bipolar memory
11/60 1977 UNIBUS 18-bit writable control store
11/23 1979 QBUS 18-bit or 22-bit 0.12
11/24 1979 UNIBUS 22-bit first UNIBUS model to use F-11 chip 0.18
11/44 1979 UNIBUS 22-bit last non-LSI PDP-11 0.42
11/23+ 1981 Nov QBUS 22-bit 0.18
11/73 1983 QBUS 22-bit first J-11 machine, 15MHz, integrated FPU, also first PMI PDP-11 0.45
11/53 1984 QBUS 22-bit S-box or standard qbus, integrated FPU, 768KiW memory 0.29
11/83 1988 QBUS 22-bit J-11 at 18MHz, integrated FPU 0.72
11/84 1988 UNIBUS 22-bit J-11 at 18MHz, integrated FPU 0.72
11/93 1990 QBUS 22-bit J-11 at 18MHz, integrated FPU, 2MiW onboard memory 1.0
11/94 1990 UNIBUS 22-bit J-11 at 18MHz, integrated FPU, 2MiW onboard memory 1.0

[*]The name PDP-11/10 was recycled by DEC from an earlier KA-11 CPU-based 11/10 from 1969, or at least it existed in advertisements[1]

See also