PDP-11

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The PDP-11 is a series of computers introduced in 1970 by Digital Equipment Corporation (DEC).
A loaded PDP-11/23 PLUS

The machine word size was 16 bits. For more information about the architecture itself, see PDP-11 architecture.

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.

PDP-11 Models and notes

Model Introduced Bus Type Addressing Notes
11/20 1970 UNIBUS 16-bit
11/05 1972 UNIBUS 16-bit
11/10 1972 UNIBUS 16-bit
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
11/03 1975 QBUS 16-bit first QBUS model, first F-11
11/34 1976 UNIBUS 18-bit
11/04 1976 UNIBUS 16-bit
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
11/24 1979 UNIBUS 22-bit first UNIBUS model to use F-11 chip
11/44 1979 UNIBUS 22-bit last non-LSI PDP-11
11/23+ 1981 Nov QBUS 22-bit
11/73 1983 QBUS 22-bit first J-11 machine, 15MHz, integrated FPU, also first PMI PDP-11
11/53 1984 QBUS 22-bit S-box or standard qbus, integrated FPU, 768KiW memory
11/83 1988 QBUS 22-bit J-11 at 18MHz, integrated FPU
11/84 1988 UNIBUS 22-bit J-11 at 18MHz, integrated FPU
11/93 1990 QBUS 22-bit J-11 at 18MHz, integrated FPU, 2MiW onboard memory
11/94 1990 UNIBUS 22-bit J-11 at 18MHz, integrated FPU, 2MiW onboard memory