Editing PDP-1 (section)

==Description==
[[File:Steve Russell and PDP-1.png|thumb|right|PDP-1 at the [[Computer History Museum]] with [[Steve Russell (computer scientist)|Steve Russell]], creator of ''[[Spacewar (video game)|Spacewar!]]'' The large cabinet houses the processor. The main control panel is just above the desk, the paper tape reader is above it (metallic), and the output of the Teletype model BRPE paper tape punch above that (vertical slot). A storage tray for eight fanfold paper tapes is attached to the top panel. At the left is the [[IBM Electric typewriter|IBM Model B]] [[typewriter]] modified by Soroban Engineering, and the Type 30 CRT display is to the far right.]]

The PDP-1 uses an [[18-bit]] [[word (computer architecture)|word]] size and has 4096 words as standard [[main memory]] (equivalent in bit size to 9,216 eight-bit [[byte]]s, but in character size to 12,388 bytes since the system actually divides an 18-bit word into three six-bit characters), upgradable to 65,536 words. The [[magnetic-core memory]]'s cycle time is 5.35 [[microsecond]]s (corresponding roughly to a [[clock speed]] of 187 [[kilohertz]]); consequently most arithmetic instructions take 10.7 microseconds (93,458 operations per second) because they use two memory cycles: the first to fetch the instruction, the second to fetch or store the data word. Signed numbers are represented in [[ones' complement]]. The PDP-1 has computing power roughly equivalent to a 1996 pocket organizer and a little less memory.<ref>{{Cite book |last1=Hafner |first1=Katie |url=https://archive.org/details/wherewizardsstay00haf_vgj/page/85 |title=Where wizards stay up late : the origins of the Internet |last2=Lyon |first2=Matthew |date=1996 |publisher=[[Simon and Schuster]] |isbn=978-0-684-81201-4 |edition=1st Touchstone |location=[[New York City]] |page=85 |lccn=96019533 |oclc=935805191 |ol=23262579M |author-link=Katie Hafner |url-access=registration |via=[[Internet Archive]]}}</ref>

[[File:Dec SYSTEM BUILDING BLOCKS logo.jpg|thumb|A System Building Block, seen end-on]]
[[File:Dec SYSTEM BUILDING BLOCKS 1103.jpg|thumb|System Building Blocks 1103 hex-inverter card]]
[[File:PDP-1 System Building Block No. 4106.jpg|thumb|PDP-1 System Building Block #4106, circa 1963, with a [[Quarter (United States coin)|US quarter]] – note that one transistor (yellow) has been replaced]]

The PDP-1 uses 2,700 [[transistor count|transistors]] and 3,000 diodes.<ref>{{Cite web |title=PDP-1 computer |url=http://www.computerhistory.org/revolution/digital-logic/12/273/1370 |url-status=live |archive-url=https://web.archive.org/web/20210607163900/https://www.computerhistory.org/revolution/digital-logic/12/273/1370 |archive-date=2021-06-07 |access-date=2022-03-23 |website=[[Computer History Museum]] |language=en}}</ref> It is constructed mostly of [[Digital Equipment Corporation|DEC]] 1000-series [[System Module|System Building Blocks]], using [[micro-alloy transistor|micro-alloy]] and [[micro-alloy diffused transistor]]s with a rated switching speed of 5{{nbsp}}MHz. The System Building Blocks are packaged into several [[19-inch rack]]s. The racks are themselves packaged into a single large mainframe case, with a hexagonal control panel containing switches and lights mounted to lie at table-top height at one end of the mainframe. Above the control panel is the system's standard [[input/output]] solution, a [[punched tape]] reader and writer.

The PDP-1 weighs about {{cvt|1600|lb|kg|order=flip}}.<ref>{{Cite web |last=Weik |first=Martin H. |date=March 1961 |title=Programmed Data Processor |url=http://www.ed-thelen.org/comp-hist/BRL61-p.html#PROGRAMMED-DATA-PROCESSOR |url-status=live |archive-url=https://web.archive.org/web/20220321031719/http://www.ed-thelen.org/comp-hist/BRL61-p.html#PROGRAMMED-DATA-PROCESSOR |archive-date=2022-03-21 |access-date=2018-07-06 |website=Ed Thelen's Nike Missile Web Site |series=A Third Survey of Domestic Electronic Digital Computing Systems |language=en}}</ref>