Editing PDP-11 (section)

== Models ==
The PDP–11 processors tend to fall into several natural groups depending on the original design upon which they are based and which I/O [[Bus (computing)|bus]] they use. Within each group, most models were offered in two versions, one intended for [[Original equipment manufacturer|OEMs]] and one intended for end-users. Although all models share the same instruction set, later models added new instructions and interpreted certain instructions slightly differently. As the architecture evolved, there were also variations in handling of some processor status and control registers.

=== Unibus models ===
[[File:Digital PDP11-IMG 1498 cropped.jpg|thumb|Original PDP–11/20 front panel]]
[[File:Pdp-11-70-panel.jpg|thumb|Original PDP–11/70 front panel]]
[[File:PDP-11-70-DDS570.jpg|thumb|Later PDP–11/70 with disks and tape]]

The following models use the [[Unibus]] as their principal bus:
* PDP–11/20 and PDP–11/15 – 1970.<ref name=pdp-11-faq-models>{{cite web |url=http://www.village.org/pdp11/faq.pages/11model.html |title=The PDP-11 FAQ |publisher=Village.org |date=2000-04-18 |access-date=2014-04-14 |url-status=dead |archive-url=https://web.archive.org/web/20160618161413/http://www.village.org/pdp11/faq.pages/11model.html |archive-date=2016-06-18 }}</ref> The 11/20 sold for $11,800.<ref>{{cite web |url=http://vintagecomputer.net/digital/PDP11-20/PDP11_Price-List_19691215.pdf |title=PDP-11 Price List (1969) |access-date=2020-10-19 |archive-date=2024-07-01 |archive-url=https://web.archive.org/web/20240701172332/http://vintagecomputer.net/digital/PDP11-20/PDP11_Price-List_19691215.pdf |url-status=live }}</ref> The original, non-microprogrammed processor was designed by Jim O'Loughlin. [[Floating point]] is supported by [[peripheral]] options using various data formats. The 11/20 lacks any kind of [[memory protection]] hardware unless retrofitted with a KS-11 [[Memory-mapped I/O|memory mapping]] add-on.<ref name="Ritchie">{{cite web |first=Dennis M. |last=Ritchie |author-link=Dennis Ritchie |title=Odd Comments and Strange Doings in Unix |url=https://www.bell-labs.com/usr/dmr/www/odd.html |publisher=[[Bell Labs]] |date=22 June 2002 |access-date=18 October 2015 |archive-date=3 January 2016 |archive-url=https://web.archive.org/web/20160103171003/http://www.bell-labs.com/usr/dmr/www/odd.html |url-status=live }}</ref> There was also a very stripped-down 11/20 at first called the 11/10,{{citation needed|date=August 2023}} but this number was later re-used for a different model.
* PDP–11/45 (1972),<ref name=pdp-11-faq-models/> PDP–11/50 (1973),<ref>{{Cite web |title=When was the PDP-11/50 released? |url=https://retrocomputing.stackexchange.com/a/28404/7208 |access-date=2024-02-05 |website=Retrocomputing Stack Exchange |language=en |archive-date=2024-07-01 |archive-url=https://web.archive.org/web/20240701172338/https://retrocomputing.stackexchange.com/questions/28397/when-was-the-pdp-11-50-released/28404#28404 |url-status=live }}</ref> and PDP–11/55 (1976)<ref name=pdp-11-faq-models/> – A much faster microprogrammed processor that can use up to 256&nbsp;[[kilobyte|KB]] of semiconductor memory instead of or in addition to [[Magnetic-core memory|core memory]] and support memory mapping and protection.{{r|Ritchie}} It was the first model to support an optional FP11 floating-point [[coprocessor]], which established the format used in later models.
* PDP–11/35 and PDP–11/40 – 1973.<ref name=pdp-11-faq-models/> [[Microprogram]]med successors to the PDP–11/20; the design team was led by Jim O'Loughlin.
* PDP–11/05 and PDP–11/10 – 1972.<ref name=pdp-11-faq-models/> A cost-reduced successor to the PDP–11/20. DEC Datasystem 350 models from 1975 include the PDP–11/10.<ref>{{cite journal |author=<!--Staff writer(s); no by-line.--> |date=July 30, 1975 |title=Time-Sharing Uses Emphasized for DEC Datasystem 350 Series |url=https://books.google.com/books?id=jT2fQqJplN8C&pg=PT29 |journal=Computerworld |volume=IX |issue=31 |pages=19 |access-date=November 4, 2022 |quote=All DEC Datasystem 350 models have PDP–11/10 CPUs |archive-date=March 6, 2023 |archive-url=https://web.archive.org/web/20230306042705/https://books.google.com/books?id=jT2fQqJplN8C&pg=PT29 |url-status=live }}</ref>
* PDP–11/70 – 1975.<ref name=pdp-11-faq-models/> The 11/45 architecture expanded to allow 4&nbsp;[[megabyte|MB]] of physical memory segregated onto a private memory bus, 2&nbsp;KB of cache memory, and much faster I/O devices connected via the Massbus.
* PDP–11/34 (1976<ref name=pdp-11-faq-models/>) and PDP–11/04 (1975<ref name=pdp-11-faq-models/>) – Cost-reduced follow-on products to the 11/35 and 11/05; the PDP–11/34 concept was created by Bob Armstrong. The 11/34 supports up to 256&nbsp;kB of Unibus memory. The PDP–11/34a (1978)<ref name=pdp-11-faq-models/> supports a fast floating-point option, and the 11/34c (same year) supported a [[cache memory]] option.
* PDP–11/60 – 1977.<ref name=pdp-11-faq-models/> A PDP–11 with user-writable microcontrol store; this was designed by another team led by Jim O'Loughlin.
* PDP–11/44 – 1979.<ref name=pdp-11-faq-models/> A replacement for the 11/45 and 11/70, introduced in 1980, that supports optional (though apparently always included) cache memory, optional FP-11 floating-point processor (one circuit board, using sixteen [[AMD]] [[Am2900|Am2901]] bit slice processors), and optional commercial instruction set (CIS, two boards). It includes a sophisticated serial console interface and support for 4&nbsp;MB of physical memory. The design team was managed by John Sofio. This was the last PDP–11 processor to be constructed using discrete [[logic gate]]s; later models were all microprocessor-based. It was also the last PDP–11 system architecture created by [[Digital Equipment Corporation]], later models were VLSI chip realizations of the existing system architectures.
* PDP–11/24 – 1979.<ref name=pdp-11-faq-models/> First VLSI PDP–11 for Unibus, using the "Fonz-11" (F11) chip set with a Unibus adapter.
* PDP–11/84 – 1985–1986.<ref name=pdp-11-faq-models/> Using the VLSI [[DEC J-11|"Jaws-11"]] (J11) chip set with a Unibus adapter.
* PDP–11/94 – 1990.<ref name=pdp-11-faq-models/> J11-based, faster than 11/84.

=== Q-bus models ===
[[File:DEC LSI11-23.jpg|thumb|A PDP–11/03 with cover removed to show the CPU board, with memory board beneath (Two of the CPU chipset's four 40-pin packages have been removed, and the optional [[Floating-point unit|FPU]] is also missing.)]]

The following models use the [[Q-Bus]] as their principal bus:
* PDP–11/03 (also known as the LSI-11/03) – The first PDP–11 implemented with [[Integrated circuit#LSI|large-scale integration]] ICs, this system uses a four-package [[MCP-1600]] chipset from Western Digital and supports 60&nbsp;KB of memory.
* {{visible anchor|PDP-11/23}} – Second generation of LSI (F-11). Early units supported only 248&nbsp;KB of memory.
* PDP–11/23+/MicroPDP–11/23 – Improved 11/23 with more functions on the (larger) processor card. By mid-1982, the 11/23+ supported 4 MB of memory.<ref>{{cite magazine |magazine=Hardcopy |date=October 1982 |page=9 |title=TSX-Plus: Time Share RT-11}}</ref>
* [[PDP-11/73|MicroPDP–11/73]] – The third generation LSI-11, this system uses the faster "Jaws-11" ([[DEC J-11|J-11]]) chip set and supports up to 4&nbsp;MB of memory.
* MicroPDP–11/53 – Slower 11/73 with on-board memory.
* MicroPDP–11/83 – Faster 11/73 with PMI (private memory interconnect).
* MicroPDP–11/93 – Faster 11/83; final DEC Q-Bus PDP–11 model.
* KXJ11 – Q-Bus card (M7616) with PDP–11 based peripheral processor and DMA controller. Based on a J11 CPU equipped with 512&nbsp;KB of RAM, 64&nbsp;KB of ROM, and parallel and serial interfaces.
* [[Mentec#M100|Mentec M100]] – Mentec redesign of the 11/93, with J-11 chipset at 19.66&nbsp;MHz, four on-board serial ports, 1-4&nbsp;MB of on-board memory, and optional FPU.
* [[Mentec#M11|Mentec M11]] – Processor upgrade board; microcode implementation of PDP–11 instruction set by Mentec, using the TI 8832 ALU and TI 8818 microsequencer from [[Texas Instruments]].
* [[Mentec#M1|Mentec M1]] – Processor upgrade board; microcode implementation of PDP–11 instruction set by Mentec, using [[Atmel]] 0.35&nbsp;[[Micrometre|μm]] [[Application-specific integrated circuit|ASIC]].<ref>{{cite web |url=http://www.fuse-network.com/fuse/demonstration/30/24675/24675.pdf |title=Development Project Report |access-date=2014-04-14 |url-status=dead |archive-url=https://web.archive.org/web/20160412201307/http://www.fuse-network.com/fuse/demonstration/30/24675/24675.pdf |archive-date=2016-04-12 }}</ref>
* Quickware QED-993 – High performance PDP–11/93 processor upgrade board.
* DECserver 500 and 550 LAT terminal servers DSRVS-BA using the KDJ11-SB chipset
[[File:DEC-PDT-11-150.jpg|thumb|The PDT-11/150 smart terminal system had two 8-inch floppy disc drives.]]

=== Models without standard bus ===
* PDT-11/110
* PDT-11/130
* PDT-11/150

The PDT series were desktop systems marketed as "smart terminals". The /110 and /130 were housed in a [[VT100]] terminal enclosure. The /150 was housed in a table-top unit which included two 8-inch floppy drives, three asynchronous serial ports, one printer port, one modem port and one synchronous serial port and required an external terminal. All three employed the same chipset as used on the LSI-11/03 and LSI-11/2 in four "microm"s. There is an option which combines two of the microms into one dual carrier, freeing one socket for an EIS/FIS chip. The /150 in combination with a [[VT100#Variants|VT105]] terminal was also sold as [[MiniMINC]], a budget version of the [[MINC-11]].
[[File:DEC VT100 terminal.jpg|thumb|VT100 terminal]]
* PRO-325
* PRO-350
* PRO-380

The [[DEC Professional (computer)|DEC Professional]] series are desktop PCs intended to compete with IBM's earlier [[Intel 8088|8088]] and [[Intel 80286|80286]] based personal computers. The models are equipped with 5{{frac|1|4}} inch floppy disk drives and hard disks, except the 325 which has no hard disk. The original operating system was P/OS, which was essentially [[RSX-11]]M+ with a menu system on top. As the design was intended to avoid software exchange with existing PDP–11 models, the poor market response was unsurprising. The [[RT-11]] operating system was eventually ported to the PRO series. A port of the [[RSTS/E]] operating system to the PRO series was also done internal to DEC, but it was not released. The PRO-325 and -350 units are based on the DCF-11 ("Fonz") chipset, the same as found in the 11/23, 11/23+ and 11/24. The PRO-380 is based on the DCJ-11 ("Jaws") chipset, the same as found in the 11/53,73,83 and others, though running only at 10&nbsp;MHz because of limitations in the support chipset.

=== Models that were planned but never introduced ===
* PDP–11/74 – A PDP–11/70 that was extended to contain multiprocessing features. Up to four processors could be interconnected, although the physical cable management became unwieldy. Another variation on the 11/74 contained both the multiprocessing features and the Commercial Instruction Set. A substantial number of prototype 11/74s (of various types) were built and at least two multiprocessor systems were sent to customers for beta testing, but no systems were ever officially sold. A four processor system was maintained by the RSX-11 operating system development team for testing and a [[uniprocessor]] system served PDP–11 engineering for general purpose timesharing. The 11/74 was due to be introduced around the same time as the announcement of the new 32-bit product line and the first model: the VAX 11/780. The 11/74 was cancelled because of concern for its field maintainability,<ref>{{cite web|title=Multiprocessor FAQ|year=2005|publisher=Machine Intelligence|author1=Bruce Mitchell|author2=Brian S. McCarthy|url=http://www.miim.com/faq/hardware/multipro.shtml|access-date=August 20, 2019}}{{Dead link|date=March 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> though employees believed the real reason was that it outperformed the 11/780<ref>{{cite mailing list|url=http://www.classiccmp.org/pipermail/cctech/2006-February/057197.html|title=Original 11/74 front panel|author=Don North|date=February 7, 2006|mailing-list=cctech|archive-url=https://web.archive.org/web/20110718232453/http://www.classiccmp.org/pipermail/cctech/2006-February/057197.html|archive-date=July 18, 2011|access-date=March 15, 2007|url-status=dead}}</ref> and would inhibit its sales. In any case, DEC never entirely migrated its PDP–11 customer base to the VAX. The primary reason was not performance, but the PDP–11's superior real-time responsiveness.{{citation needed|date=May 2011}}
* PDP–11/27 – A Jaws-11 implementation that would have used the [[VAXBI Bus]] as its principal I/O bus.
* PDP–11/68 – A follow-on to the PDP–11/60 that would have supported 4&nbsp;MB of physical memory.

[[File:GT40 Lunar Lander.jpg|thumb|DEC GT40 running ''[[Lunar Lander (video game genre)|Moonlander]]''|229x229px]]

=== Special-purpose versions ===
* [[DEC GT40|GT40]] – VT11 [[vector graphics]] terminal using a PDP–11/10.<ref name="gt40/42">{{Cite web |date=February 1975 |title=GT40/GT42 user's guide |url=http://www.bitsavers.org/pdf/dec/graphics/VT11/EK-GT40-OP-002_GT40_GT42_Users_Guide_Feb75.pdf |page=29 |access-date=2022-12-22 |archive-date=2022-12-22 |archive-url=https://web.archive.org/web/20221222163442/http://www.bitsavers.org/pdf/dec/graphics/VT11/EK-GT40-OP-002_GT40_GT42_Users_Guide_Feb75.pdf |url-status=live }}</ref>
* GT42 – VT11 vector graphics terminal using a PDP–11/10.<ref name="gt40/42" />
* GT44 – VT11 vector graphics terminal using a PDP–11/40.
* GT62 – VS60 vector graphics workstation using a PDP–11/34a and VT48 graphics processor.
* [[Heathkit H11|H11]] – [[Heathkit]] OEM version of the LSI-11/03.
* VT20 – Terminal with PDP–11/05 with direct mapped character display for text editing and typesetting (predecessor of the VT71).
* [[File:PDP-11-34 front panel.jpg|thumb|229x229px|PDP–11/34 front panel which was a replacement for toggle switches in earlier PDP–11 computers]]VT71 – Terminal with LSI-11/03 and Q-Bus backplane with direct mapped character display for text editing and typesetting.
* [[VT103]] – VT100 with backplane to host an LSI-11.
* VT173 – A high-end editing terminal containing an 11/03, which loaded its editing software over a serial connection to a host minicomputer. Used in various publishing environments, it was also offered with DECset, Digital's VAX/VMS 3.x native mode OEM version of the [[Datalogics]] Pager automated batch composition engine. When VT173 inventory was exhausted in 1985, Digital discontinued DECset and transferred its customer agreements to Datalogics. (HP now uses the name HP [[DECset]] for a software development toolset product.)[[File:DEC-MINC-23.jpg|thumb|MINC-23 laboratory computer|229x229px]]
{{anchor|MINC-11}}
* [[MINC-11]] – Laboratory system based on 11/03 or 11/23;<ref>{{cite web|url=http://www.binarydinosaurs.co.uk/Museum/Digital/minc/index.php |title=Digital MINC-11 |publisher=Binary Dinosaurs |access-date=2014-04-14}}</ref> when based on the 11/23, it was sold as a 'MINC-23', but many MINC-11 machines were field-upgraded with the 11/23 processor. Early versions of the MINC-specific software package would not run on the 11/23 processor because of subtle changes in the instruction set; MINC 1.2 is documented as compatible with the later processor.
* [[C.mmp]] – Multiprocessor system from [[Carnegie Mellon University]].
[[File:Unimation controller internals.jpg|thumb|This [[Unimation]] robot arm controller used DEC LSI-11 series hardware.|229x229px]]
* The [[Unimation]] robot arm controllers used Q-Bus LSI-11/73 systems with a DEC M8192 / KDJ11-A processor board and two DEC DLV11-J (M8043) async serial interface boards.
* SBC 11/21 (boardname KXT11) Falcon and Falcon Plus – single board computer on a Q-Bus card implementing the basic PDP–11 instruction set, based on T11 chipset containing 32&nbsp;KB static RAM, two ROM sockets, three serial lines, 20&nbsp;bit parallel I/O, three interval timers and a two-channel DMA controller. Up to 14&nbsp;Falcons could be placed into one Q-Bus system.
* KXJ11 Q-Bus card (M7616) with PDP–11 based peripheral processor and DMA controller. Based on a J11 CPU equipped with 512&nbsp;KB RAM, 64&nbsp;KB ROM and parallel and serial interfaces.
* HSC high end CI disk controllers used backplane mounted J11 and F11 processor cards to run the CHRONIC operating system.<ref name="ReferenceA">{{cite book|url=http://vaxhaven.com/images/b/ba/EK-HSCMN-IN-002.pdf|id=EK-HSCMN-IN-002|title=HSC Controller Installation Manual|at=p. 4-28|date=July 1991|publisher=Digital Equipment Corporation|access-date=2017-05-29|archive-date=2019-09-03|archive-url=https://web.archive.org/web/20190903150133/http://vaxhaven.com/images/b/ba/EK-HSCMN-IN-002.pdf|url-status=live}}</ref>
* VAX Console – The [[DEC Professional (computer)|DEC Professional Series]] PC-38N with a real-time interface (RTI) was used as the console for the [[VAX 8000|VAX 8500 and 8550]]. The RTI has two serial line units: one connects to the VAX environmental monitoring module (EMM) and the other is a spare that could be used for data transfer. The RTI also has a programmable peripheral interface (PPI) consisting of three 8-bit ports for transferring data, address, and control signals between console and the VAX console interface.<ref>{{cite book |author=<!--Staff writer(s); no by-line.--> |title=VAX 8500/8550 System Hardware User's Guide |publisher=Digital Equipment Corporation |pages=1–8 |date=1986 }}</ref>
* [[DEC T-11|T-11]] is a microprocessor that implements the PDP-11 instruction set architecture. It was developed for embedded systems and was the first single-chip microprocessor developed by DEC. It was sold on the open market.<ref>{{cite web |date=March 24, 1982 |title=T-11 Engineering Specification |url=http://www.bitsavers.org/pdf/dec/pdp11/t11/T11_Engineering_Specification_Rev_E_Mar82.pdf |access-date=May 15, 2023 |archive-date=March 8, 2023 |archive-url=https://web.archive.org/web/20230308003715/http://www.bitsavers.org/pdf/dec/pdp11/t11/T11_Engineering_Specification_Rev_E_Mar82.pdf |url-status=live }}</ref>

=== Unlicensed clones ===
The PDP–11 was sufficiently popular that many unlicensed PDP–11-compatible minicomputers and microcomputers were produced in [[Eastern Bloc]] countries. Some were pin-compatible with the PDP–11 and could use its peripherals and system software. These include:
* [[SM-4]], [[SM-1420]], [[SM-1600]], [[Electronika 100-25]], [[Electronika BK]] series, [[Electronika 60]], [[Electronika 85]], [[DVK]], [[UKNC]], and some models of the [[SM EVM]] series (in the [[Soviet Union]]).
* [[SM-4]], [[SM-1420]], [[IZOT-1016]] and peripherals (in [[Bulgaria]]).
* MERA-60 in [[Poland]].
* SM-1620, SM-1630 (in [[East Germany]]).
* [[SM-4]], TPA-1140,<ref>{{Cite web |title=Múzeum - KFKI TPA 1140 |url=http://hampage.hu/tpa/e_tpa1140.html |access-date=2023-04-30 |website=hampage.hu |archive-date=2023-04-06 |archive-url=https://web.archive.org/web/20230406010424/http://hampage.hu/tpa/e_tpa1140.html |url-status=live }}</ref> TPA-1148,<ref>{{cite web |author=Ákos Varga |url=http://hampage.hu/tpa/e_tpa1148.html |title=TPA-1148 |publisher=Hampage.hu |access-date=2014-04-14 |archive-date=2015-07-12 |archive-url=https://web.archive.org/web/20150712212348/http://hampage.hu/tpa/e_tpa1148.html |url-status=live }}</ref> TPA-11/440<ref>{{cite web |author=Ákos Varga |url=http://hampage.hu/tpa/e_tpa11440.html |title=TPA-11/440 |publisher=Hampage.hu |access-date=2014-04-14 |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303235921/http://hampage.hu/tpa/e_tpa11440.html |url-status=live }}</ref> (in [[Hungary]]).
* SM-4/20, SM {{not a typo|52-11}}, JPR-12R (in Czechoslovakia).
* CalData – Made in US, ran all DEC OSes.<ref>{{cite web |url=http://www.bitsavers.org/pdf/calData/CalData_Brochures_1974.pdf |title=CalData_brochure |access-date=2014-04-14 |archive-date=2012-09-12 |archive-url=https://web.archive.org/web/20120912170014/http://www.bitsavers.org/pdf/calData/CalData_Brochures_1974.pdf |url-status=live }}</ref> The CalData hardware was sufficiently DEC-compatible that CalData memory boards could be used in DEC PDP–11 systems.
* CORAL series (made at [[ICE Felix]] in [[Bucharest]]) and the INDEPENDENT series (made at ITC [[Timișoara]])<ref name="Dragomirescu2003">{{cite book|author=Ion Glodeanu (coord.), Oscar Hoffman, Doina Dragomirescu|title=Actorii sociali ai promovării tehnologiilor, informaţiei şi comunicaţiilor|url=https://books.google.com/books?id=Z2aoVu7XheMC&pg=PA122|year=2003|publisher=Editura Mica Valahie|isbn=978-973-85884-4-8|page=122|language=ro|access-date=2014-04-14}}</ref> running the [[RSX-11M]] operating system (in [[Romania]]). The CORAL series had several models: the CORAL 4001 was roughly equivalent to the PDP–11/04, the CORAL 4011 was a PDP 11/34 clone, while the CORAL 4030 was a PDP–11/44 clone.<ref>{{Cite web |url=http://uknc.narod.ru/Doc/rt11book.txt |title=Archived copy |access-date=2014-02-13 |archive-url=https://web.archive.org/web/20140223131154/http://uknc.narod.ru/Doc/rt11book.txt |archive-date=2014-02-23 |url-status=dead }}</ref> These were used in state-owned companies and in public universities, originally operated with [[punched card]]s, later through video terminals like the Romanian [[DAF-2020]], to teach FORTRAN and Pascal, until replaced by IBM PC compatibles, starting in 1991.
* [[Systime Computers]] models 1000, 3000, 5000 – OEM agreement for sales in the UK and Western Europe, but disputes originated over both intellectual property infringement and indirect sales to the [[Eastern Bloc]].<ref>{{cite news | url=<!--BD https://www.cbronline.com/news/systime_sets_80386_s_series_box_100_user_unix_system/ -->| title=Systime sets 80386 S-series box, 100-user Unix System | work=[[Computergram International]] | publisher=Computer Business Review | date=1 February 1987}}</ref><ref>{{cite news | url=https://books.google.com/books?id=Vzni1LqxEEsC&pg=PA29 | title=Who will tear the Silicon Curtain? | author-first=Mary | author-last=Fagan | magazine=New Scientist | date=24 September 1987 | pages=28–29 }}{{Dead link|date=November 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>