The PDP-11 is a series of minicomputers introduced in 1969  by the Digital Equipment Corporation (DEC), in production by them from 1970-1990. Their life-time spanned a period of momentous changes in the computer world: when they were first introduced (and for a little less than half their life), core memory was still the standard main memory technology; by the end, microprocessors had become ubiquitous.
The machine word size was 16 bits, and it was a general register architecture. Although it was not the first to feature the latter, its wide distribution (in 1980, it was the world's best-selling computer) has helped influence almost all later machines to follow that path.
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.
Towards the end of its life, there were several microcomputer implementations of the PDP-11, as chips.
It could run a variety of operating systems. Many were produced by DEC themselves, but several were produced by third-parties. It was the machine which made UNIX, which now seems to have taken over the world (in the form of Linux) widely known and popular, with UNIX Sixth Edition. Often DEC would purchase or re-brand such an OS and re-sell it as their own product; for example, UNIX sold as Ultrix by DEC.
After DEC discontinued production of PDP-11's, the line was sold to Mentec, who produced a few newer models.
Unix based Operating Systems
- UNIX First Edition
- UNIX Second Edition
- UNIX Third Edition
- UNIX Fourth Edition
- UNIX Fifth Edition
- UNIX Sixth Edition
- Unix Seventh Edition
These are the original Bell Laboratories releases of Unix; the first 4 were only internal to Bell, the Fifth saw limited distribution outside it, and the Sixth took over the world.
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 BSD 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 experience one can get going to get on a 16-bit mini.
PDP-11 Models and notes
|Model||Introduced||Bus Type||Addressing||Notes||Speed (VUPS)|
|11/55||1976||UNIBUS||18-bit||fast bipolar memory|
|11/03||1975||QBUS||16-bit||first QBUS model||0.5|
|11/60||1977||UNIBUS||18-bit||writable control store|
|11/23||1979||QBUS||18-bit or 22-bit||first F-11||0.12|
|11/24||1979||UNIBUS||22-bit||only UNIBUS model to use F-11 chip||0.18|
|11/44||1979||UNIBUS||22-bit||last non-LSI PDP-11||0.42|
|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 KA11 CPU-based 11/10 from 1969, or at least it existed in advertisements
- PDP11 - Documentation at Bitsavers
- PDP-11 Recognition - Illustrated guide to identifying PDP-11 models
- A brief tour of the PDP-11, the most influential minicomputer of all time - has some minor errors, but generally good
- What Have we Learned From the PDP-11? - a retrospective on a group of papers by Gordon Bell
|v • d • e PDP-11 Computers and Peripherals|
|UNIBUS PDP-11s - PDP-11/20 • PDP-11/15 • PDP-11/35 • PDP-11/40 • PDP-11/45 • PDP-11/50 • PDP-11/55 • PDP-11/70 • PDP-11/05 • PDP-11/10 • PDP-11/34 • PDP-11/04 • PDP-11/44 • PDP-11/60 • PDP-11/24 • PDP-11/84 • PDP-11/94|