PDP-11

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