PDP-4

{{Short description|1962 computer made by Digital Electronics Corp}}

{{Infobox computing device

| name = PDP-4

| title =

| aka =

| logo = PDP-4 wordmark.svg

| image = Photograph of Exhibit of PDP-4 Digital Equipment Corporation Machines on the Stage of the National Archives Auditorium, 1964 (3874706978).jpg

| caption = The PDP-4 on display at NARA's auditorium stage in Washington, D.C., 1964

| developer = Digital Equipment Corporation

| manufacturer =

| family = Programmed Data Processor

| type = Minicomputer

| generation =

| releasedate = {{Start date and age|1962}}

| lifespan =

| price = {{USD|65,000|1962}}

| discontinued =

| unitssold = Approximately 54

| unitsshipped =

| media = Paper tape

| os =

| power =

| soc =

| cpu =

| memory =

| storage =

| memory card =

| display =

| graphics =

| sound =

| input =

| controllers =

| camera =

| touchpad =

| connectivity =

| platform = DEC 18-bit

| service =

| dimensions =

| weight = {{Convert|1090|lb|kg}}

| topgame =

| compatibility =

| predecessor = PDP-1

| successor = PDP-7

| related =

| website =

}}

The PDP-4 was the successor to the Digital Equipment Corporation's PDP-1.

History

This 18-bit machine, first shipped in 1962,{{cite book |title=Portraits in Silicon |page=[https://archive.org/details/portraitsinsilic00slat/page/210 210] |author=Robert Slater |date=1989 |publisher=MIT Press |isbn=0262691310 |url=https://archive.org/details/portraitsinsilic00slat/page/210 }} was a compromise: "with slower memory and different packaging" than the PDP-1, but priced at $65,000 - less than half the price of its predecessor.{{rp|p.4}} All later 18-bit PDP machines (7, 9 and 15) are based on a similar, but enlarged instruction set, more powerful than, but based on the same concepts as, the 12-bit PDP-5/PDP-8 series.

Approximately 54 were sold.{{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}}

Hardware

File:Teletype Model 28 KSR Keyboard.png ASR, with a built in paper tape reader and paper tape punch.]]

The system's memory cycle is 8 microseconds, compared to 5 microseconds for the PDP-1.{{cite book

|title=A History of Modern Computing |page=[https://archive.org/details/historyofmodernc00ceru_0/page/209 209]

|url=https://archive.org/details/historyofmodernc00ceru_0 |url-access=registration |isbn=978-0262532037

|author=Paul E. Ceruzzi |date=2012|publisher=MIT Press

}}{{cite book |date=2014

|title=Computer Engineering: A DEC View of Hardware Systems Design

|url=https://books.google.com/books?isbn=1483221105 |isbn=978-1483221106

}}

The PDP-4 weighs about {{Convert|1090|lb|kg}}.{{Cite web|url=http://www.ed-thelen.org/comp-hist/BRL64-p.html#PROGRAMMED-DATA-PROCESSOR-4|title=PROGRAMMED DATA PROCESSOR 4|last=Weik|first=Martin H.|date=Jan 1964|website=ed-thelen.org|series=A Fourth Survey of Domestic Electronic Digital Computing Systems}}

Mass storage

Both the PDP-1 and the PDP-4 were introduced as paper tape-based systems.{{cite web

|url=http://www.soemtron.org/downloads/decinfo/architecture18b-08102006.pdf

|title=Architectural Evolution in DEC's 18b Computers |author=Bob Supnik}} The only use, if any, for IBM-compatible 200 BPI or 556 BPI magnetic tape{{cite book

|url=http://www.soemtron.org/downloads/decinfo/pdp7brochure1.pdf

|title=Brochure F-71 - "Programmed Data Processor - 7" |date=1964

|publisher=Digital Equipment Corporation}} was for data. The use of "mass storage" drums - not even a megabyte and non-removable - were an available option, but were not in the spirit of the “personal” or serially shared systems that DEC offered.

It was in this setting that DEC introduced DECtape, initially called "MicroTape", for both the PDP-1 and PDP-4.