View source for PDP-9

{{Short description|18-bit computer from Digital, 1966}}
{{Infobox computing device
| name         = PDP-9
| title        =
| aka          =
| logo         = PDP-9 wordmark.svg
| image        = File:PDP-9.jpg
| image_size   = 
| caption      =
| developer    = [[Digital Equipment Corporation]]
| manufacturer =
| family       = [[Programmed Data Processor]]
| type         = [[Minicomputer]]
| generation   =
| releasedate  = {{Start date and age|1966}}
| lifespan     =
| price        = 
| discontinued =
| unitssold    = 445
| unitsshipped =
| media        = [[Paper tape]], [[DECtape]]
| os           =
| power        =
| soc          =
| cpu          =
| memory       =
| storage      =
| memory card  =
| display      =
| graphics     =
| sound        =
| input        =
| controllers  =
| camera       =
| touchpad     =
| connectivity =
| platform     = DEC 18-bit
| service      =
| dimensions   =
| weight       = {{convert|750|lb|kg}}
| topgame      =
| compatibility=
| predecessor  = [[PDP-7]]
| successor    = [[PDP-15]]
| related      =
| website      =
}}
[[File:PDP9-ACONIT.jpg|thumb|A PDP-9 on display at ACONIT in Grenoble, France]]

The '''PDP-9''', the fourth of the five 18-bit [[minicomputer]]s produced by [[Digital Equipment Corporation]], was introduced in 1966.<ref name=DEC57.PRES>{{cite book   
|title=DIGITAL EQUIPMENT CORPORATION - Nineteen Fifty-Seven To The Present
|url=http://s3data.computerhistory.org/pdp-1/dec.digital_1957_to_the_present_(1978).1957-1978.102630349.pdf
|date=1975 |publisher=Digital Equipment Corporation}}</ref>{{RP|P.10}} A total of 445 PDP-9 systems were produced,<ref name=RICM>{{cite web |url=https://www.ricomputermuseum.org/collections-gallery/equipment/dec-pdp-9
|title=RI Computer Museum, DEC PDP-9, System Number 319}}</ref> of which 40 were the compact, low-cost PDP-9/L units.<ref name=Pan7>.{{cite web |url=http://www.quadibloc.com/comp/pan07.htm |title=The Early Architectures of DEC}}</ref>

==History==
The 18-bit PDP systems preceding the PDP-9 are the [[PDP-1]], [[PDP-4]] and [[PDP-7]]. Its successor is the [[PDP-15]].

==Hardware==
The PDP-9, which is "two metres wide and about 75cm deep,"<ref>{{cite web
|url=https://50years.latrobe/david-millsom  |title=David Millson - 50 years}}</ref> is approximately twice the speed of the PDP-7.  It was built using discrete transistors, and has an optional integrated [[vector graphics]] terminal. The PDP-9 has a memory cycle time of 1 microsecond, and weighs about {{convert|750|lb|kg}}.<ref name="maintenance-manual">{{cite book|url=http://www.bitsavers.org/pdf/dec/pdp9/F-97_PDP-9_MaintMan_Apr72.pdf|title=PDP-9 Maintenance Manual, Volume 1|date=April 1972}}</ref>{{rp|pages=1{{hyphen}}7-1{{hyphen}}8}}  The PDP-9/L has a memory cycle time of 1.5 microseconds, and weighs about {{convert|900|lb|kg}}.<ref>{{cite book|title=PDP-9/L User Handbook|url=http://www.bitsavers.org/pdf/dec/pdp9/pdp9l/DEC-9L-GRVA-D_PDP9L_Hbk.pdf|pages=|date=June 1968}}</ref>{{rp|page=1{{hyphen}}1, 15{{hyphen}}8}}

It is DEC's first microprogrammed machine.<ref>{{cite book|chapter-url=https://books.google.com/books?id=SDOoBQAAQBAJ&pg=PA154|title=Computer Engineering: A DEC View of Hardware Systems Design|chapter=Chapter 6: The PDP-1 and Other 18-bit Computers|author1=C. Gordon Bell|authorlink1=Gordon Bell|author2=Gerald Butler|author3=Robert Gray|author4=John E. McNamara|author5=Donald Vonada|author6=Ronald Wilson|pages=154–155|editor1=C. Gordon Bell|editor2=J. Craig Mudge|editor3=John E. McNamara|publisher=[[Digital Press]]|year=1978|isbn=0-932376-00-2}}</ref><ref name="maintenance-manual"/>{{rp|page=3{{hyphen}}16}}

A typical configuration included:<ref name=RICM/>
* 300 cps [[paper tape]] reader
* 50 cps paper tape punch
* [[DECtape]] for operating system and user files
* 10 cps [[Teletype Model 33|console teleprinter, Model 33 KSR]]
[[File:Teletype-IMG 7287.jpg|thumb|Model 33 Teleprinter, similar to the PDP-9's console device, though the PDP-9 had faster dedicated paper tape devices instead of the integrated reader/punch.]]

Among the improvements of the PDP-9 over its PDP-7 predecessor are:
* the addition of status flags for reader and punch errors, thus providing added flexibility and for error detection<ref name=Arc18b>{{cite web
|url=http://www.soemtron.org/downloads/decinfo/architecture18b-08102006.pdf
|title=Architectural Evolution in DEC's 18b Computers |author=Bob Supnik}}</ref>
* an entirely new design for multi-level interrupts, called the Automatic Priority Interrupt (API) option
* a more advanced form of memory management<ref>{{cite web
|url=https://github.com/parsa/simh/wiki/PDP-9-Simulator-Configuration
|title=PDP 9 Simulator Configuration |website=GitHub.com}}</ref>

User/university-based research projects for extending the PDP-9 include:
* a hardware capability for [[floating-point arithmetic]], at a time when machines in this price range used software for floating-point arithmetic<ref>{{cite thesis
|url=http://arizona.openrepository.com/arizona/handle/10150/318186
|title=Design of a floating point processor for the PDP-9 computer
|degree=MSc
|publisher=University of Arizona  |author=Ben Milton Huey  |date=1969}}</ref>
* a PDP-9 controlled parallel computer<ref>{{cite thesis
|url=http://arizona.openrepository.com/arizona/handle/10150/347638
|title=The logic design of a PDP-9 controlled parallel computer 
|degree=MSc
|publisher=University of Arizona  |author=Wokhlu, Roop Krishen  |date=1969}}</ref>

==Software==
The system came with an OS that functions as single-user keyboard monitor, called ADSS (ADvanced Software System).<ref>{{cite web
|url=http://www.bitsavers.org/pdf/dec/spd/17.06.00_7608_ADSS-B_F-15_5C.pdf
|title=Software Product Description, ADSS-B/F-15, Version SC, Advanced Software System, B/F |author=Digital Equipment Corporation}}</ref> DECsys provided an interactive, single-user, program development environment for [[Fortran]] and assembly language programs.<ref name=DECsys>{{cite web
|url=http://simh.trailing-edge.com/docs/decsys.pdf
|title=Technical Notes on DECsys   |author=Bob Supnik  |date=19 June 2006}}</ref>

Both FORTRAN II<ref name=RICM/> and FORTRAN IV<ref>{{cite web
|url=http://www.silogic.com/Athena/Hybrid%20Lab/1968%20CMU%20Hybrid%20Lab%20-%20Linkage%20-%20PDP-9%20Facilities.pdf
|title=User Manual - Linkage - PDP-9 Facilities |publisher=[[Carnegie-Mellon University]] Hybrid Computation Laboratory |date= September 1968 |access-date= 19 September 2017}}</ref> were implemented for the PDP-9.

[[MUMPS]] was originally developed on the PDP-7, and ran on several PDP-9s at the [[Massachusetts General Hospital]].<!-- need to find good refs for exactly what role the pdp-9 played in Mumps development-->

==Sales==
The [[PDP-7]], of which 120 were sold,<ref name=DEC57.PRES/>{{rp|p.8}} was described as "highly successful".<ref name=RICM/>  The PDP-9 sold 445 units. Both have submodels, the PDP-7A<ref group="NB">sometimes identified by customers and media as PDP-7/A</ref> and the PDP-9/L,<ref group="NB">yes, DEC had a "slash" for the 9/L but not for the 7A</ref> neither of which accounted for a substantial percentage of sales.<ref name=DEC57.PRES/><ref group="NB">directly mentioned for one, calculated in the other case</ref>

==See also==
* [[Programmed Data Processor]]
* [[PDP-15]] - successor to the PDP-9

==Notes==
{{reflist|group="NB"}}

==References==
{{reflist}}

{{DEC hardware}}

[[Category:DEC minicomputers]]
[[Category:18-bit computers]]
[[Category:Transistorized computers]]
[[Category:Computer-related introductions in 1966]]


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