PDP-11

a series of 16-bit [|minicomputers] manufactured and sold by Digital Equipment Corporation from 1970 into the 1990s. The PDP-11 was a little-endian machine, concerning the byte-order of 16-bit words in memory. The first officially named version of Unix ran on the PDP-11/20 in 1970. The C|C programming language was written to take advantage of PDP-11 features to rewrite Unix in a high level language. Further, the chess machine Belle by Ken Thompson and Joe Condon was composed of a PDP-11/23 with several custom boards. || toc =Photos= =Orthogonal Instruction Set= The PDP-11 processor architecture had a mostly [|orthogonal instruction set], and influenced the design of microprocessors, such as Motorola's 68000. Almost any operand could apply any of eight [|addressing modes] to eight registers R0 to R7, where R0 to R5 were general purpose registers, R6 the Stack- and R7 the instruction pointer.
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 * [[image:250px-Pdp-11-40.jpg link="https://commons.wikimedia.org/wiki/File:Pdp-11-40.jpg"]] ||~  || **PDP-11**,
 * PDP-11/40 ||~  ||^   ||
 * [[image:Ken_Thompson_and_Dennis_Ritchie_at_PDP-11.jpg link="https://commons.wikimedia.org/wiki/File:Ken_Thompson_%28sitting%29_and_Dennis_Ritchie_at_PDP-11_%282876612463%29.jpg"]] ||
 * Ken Thompson (sitting) and [|Dennis Ritchie] working together at a PDP-11, ca 1972 ||

=Unibus= A second innovation was the memory bus called [|Unibus] - input and output devices were mapped to memory addresses, and no special I/O instructions or buses were needed.

=See also=
 * 6800
 * 68000
 * PDP-1
 * PDP-6
 * PDP-8
 * PDP-10
 * Nova
 * VAX

=Publications=
 * [|Gordon Bell], Roger Cady, Harold McFarland, Bruce Delagi, J. O'Laughlin, R. Noonan, W. Wulf (**1970**). //A New Architecture for Mini-Computers - The DEC PDP-11//. [|pdf] from The Computer History Museum, [|pdf] from Microsoft Research
 * [|Gordon Bell], [|Bill Strecker] (**1975**). //What We Learned From the PDP-11//. [|pdf]

=External Links=
 * [|PDP-11 from Wikipedia]
 * [|Programmed Data Processor from Wikipedia]
 * [|PDP-11 architecture from Wikipedia]
 * [|PDP-11 - Introduction]
 * [|PDP 11/40 minicomputer system] from The Computer History Museum
 * [|PDP11/70 minicomputer] from The Computer History Museum
 * [|PDP-11] by [|Ed Thelen]
 * [|/pdf/dec/pdp11] from [|bitsavers.org]
 * [|MACRO-11 from Wikipedia] (PDP-11 Assembly)

=References= =What links here?= include component="backlinks" page="PDP-11" limit="60"
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