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{{Short description|First commercially produced personal workstation with a Graphical User Interface}}
{{distinguish|PERC (disambiguation){{!}}PERC}}
{{Use dmy dates|date=April 2022}}
[[File:ICL PERQ 1 workstation Edinburgh University.jpg|thumb|Two ICL PERQ 1 workstations]]

The '''PERQ''', also referred to as the '''Three Rivers PERQ''' or '''ICL PERQ''', is a pioneering [[workstation]] [[computer]] produced in the late 1970s through the early 1980s. It is the first commercially produced personal workstation with a [[graphical user interface]] (GUI). The design of the PERQ was heavily influenced by the original workstation computer, the [[Xerox Alto]], which was never commercially produced. The workstation was conceived by six former [[Carnegie Mellon University]] [[alumnus|alumni]] and employees: Brian S. Rosen, James R. Teter, William H. Broadley, J. Stanley Kriz, [[Raj Reddy]] and Paul G. Newbury, who formed the startup [[Three Rivers Computer Corporation]] (3RCC) in 1974.

The name "PERQ" was chosen both as an acronym of "[[Pascal (programming language)|Pascal]] Engine that Runs Quicker," and to evoke the word ''[[employee benefits|perquisite]]'' commonly called a ''perk'', that is an additional employee benefit.<ref>[http://www.chilton-computing.org.uk/acd/sus/perq_history/part_1/c3.htm PERQ History: Part I: 3. Early Days]. [http://www.chilton-computing.org.uk/ Chilton Computing], UK.</ref>

In June 1979, the company took its very first order from the UK's Rutherford Appleton Laboratory and the computer was officially launched in August 1979 at [[SIGGRAPH]] in Chicago.<ref>{{Cite web|url=http://www.chilton-computing.org.uk/acd/sus/perq_papers/perq_external/p001.htm|title=PERQ and Advanced Raster Graphics Workstations|last=|first=|date=September 1982|website=|archive-url=|archive-date=|access-date=}}</ref> 3RCC later entered into a relationship with the British computer company [[International Computers Limited]] (ICL) in 1981 for European distribution, and later co-development and manufacturing,<ref>[http://www.chilton-computing.org.uk/acd/sus/perq_history/part_3/c16.htm PERQ History: Part III: 16. Decision Time], Chilton Computing, UK.</ref> as a result of interest from the [[United Kingdom|UK]] [[Science and Engineering Research Council|Science Research Council]] (later, the Science and Engineering Research Council).

The PERQ was used in a number of academic research projects in the UK during the 1980s. 3RCC was renamed PERQ System Corporation in 1984. It went out of business in 1986, largely due to competition from other workstation manufacturers such as [[Sun Microsystems]], [[Apollo Computer]] and [[Silicon Graphics]].

Brian Rosen, one of the founders of 3RCC, also worked at [[PARC (company)|Xerox PARC]] on the [[Xerox Dolphin|Dolphin]] workstation.

==Hardware==
=== Processor ===
The PERQ [[central processing unit|CPU]] was a [[microcode]]d [[transistor–transistor logic|discrete logic]] design, rather than a [[microprocessor]]. It was based around [[74S181]] [[bit-slice]] [[arithmetic logic unit|ALU]]s and an [[AMD Am2900|Am2910]] [[Microsequencer|microcode sequencer]]. The PERQ CPU was unusual in having 20-bit wide [[Processor register|registers]] and a writable [[control store]] (WCS), allowing the microcode to be redefined.<ref name="hardware-faq">{{cite newsgroup
 | title = PERQ 2 Hardware FAQ (long)
 | author = Tony Duell
 | date = 1993-10-12
 | newsgroup = alt.sys.perq
 |message-id= 12OCT199321195696@siva.bris.ac.uk
 | url = http://groups.google.com/group/alt.sys.perq/msg/d15c89bb70505499?hl=en
 | accessdate = 2008-12-02
}}</ref> The CPU had a microinstruction cycle period of 170 [[Nanosecond|ns]] (5.88&nbsp;MHz).<ref name="sus-leaflets-1985">[http://www.chilton-computing.org.uk/acd/sus/perq_pr/p017.htm PERQ Publicity: ICL's PERQ Leaflets 1985]</ref>

===PERQ 1===
The original PERQ (also known as the ''PERQ 1''), launched in 1980, was housed in a pedestal-type cabinet with a brown fascia and an 8-inch floppy disk drive mounted horizontally at the top.

The PERQ 1 CPU had a WCS comprising 4k [[Word (data type)|word]]s of 48-bit microcode memory. The later ''PERQ 1A'' CPU extended the WCS to 16k words. The PERQ 1 could be configured with 256 KB, 1 or 2 MB of 64-bit-wide [[Random-access memory|RAM]] (accessed via a 16-bit bus),<ref name="sus-leaflets-1985"/> a 12 or 24 MB, 14-inch [[Shugart Associates|Shugart]] SA-4000-series [[hard disk drive|hard disk]], and an 8-inch [[floppy disk]] drive.<ref>[http://www.chilton-computing.org.uk/acd/sus/perq_pr/p005.htm PERQ Brochure], Chilton Computing, UK.</ref><ref name="faq"/> The internal layout of the PERQ 1 was dominated by the vertically mounted hard disk drive. It was largely this that determined the height and depth of the chassis.

A basic PERQ 1 system comprised a CPU board, a memory board (incorporating the [[framebuffer]] and monitor interface) and an [[Input/output|I/O]] board (IOB, also called CIO).<ref>[http://yahozna.dyndns.org/computers/perq/index.html Three Rivers PERQ]</ref> The IOB included a [[Zilog Z80]] [[microprocessor]], an [[IEEE-488]] interface, an [[RS-232]] [[serial port]], hard and floppy disk interfaces and [[speech synthesis]] hardware.<ref>[http://www.chilton-computing.org.uk/acd/sus/perq_pr/p002.htm PERQ Display Boards], Chilton Computing, UK.</ref> PERQ 1s also had a spare Optional I/O (OIO) board slot for additional interfaces such as [[Ethernet]].

A [[graphics tablet]] was standard. Most PERQ 1s were supplied with an 8½ ×11-inch, 768×1024 pixel, [[page orientation|portrait orientation]], white phosphor [[monochrome]] monitor.

===PERQ 2===
The ''PERQ 2'' (codenamed ''Kristmas'' during development) was announced in 1983.<ref>[http://www.chilton-computing.org.uk/acd/sus/perq_history/part_5/c20.htm PERQ History: Part V: 20. ICL Manufacturing], Chilton Computing, UK.</ref> The PERQ 2 could be distinguished from the PERQ 1 by its wider, ICL-designed cabinet, with a lighter-coloured fascia, vertical floppy disk drive and three-digit diagnostic display.

The PERQ 2 used the same 16k WCS CPU as the PERQ 1A and had a 3-button [[computer mouse|mouse]] in place of the graphics tablet. It was configured with a quieter 8-inch 35 MB [[Micropolis Corporation]] 1201 hard disk, 1 or 2 MB of RAM and had the option of the PERQ 1's portrait monitor or a 19-inch, 1280×1024 landscape orientation monitor.<ref name="sus-vii-34">[http://www.chilton-computing.org.uk/acd/sus/perq_history/part_7/c34.htm PERQ History: Part VII: 34. Hardware], Chilton Computing, UK.</ref>

Due to manufacturing problems with the original 3RCC PERQ 2 (also known as the ''K1''), ICL revised the hardware design, resulting in the ''PERQ 2 T1'' (or ICL 8222).<ref name="sus-vii-34"/>

The later ''PERQ 2 T2'' (ICL 8223) and ''PERQ 2 T4'' models replaced the 8-inch hard disk with a 5¼-inch hard disk, which also allowed for a second disk to be installed internally.

The T4 model (of which only around 10 are thought to have been produced) had an extended 24-bit CPU and [[backplane]] bus, allowing the use of a 4MB RAM board.<ref name="hardware-faq"/><ref name="faq">[http://vonhagen.org/perq-gen-faq.html#I-33 PERQ FAQ, Rev. 7]</ref>

The PERQ 2 retained the PERQ 1's OIO slot, but replaced the IOB with either an EIO (Ethernet I/O) or NIO (Non-Ethernet I/O) boards. These were similar to the IOB, with the addition of a [[non-volatile]] [[real-time clock]], a second RS-232 port, and (on the EIO board) an Ethernet interface.

=== PERQ 3 ===
The ''PERQ 3A'' (otherwise known as the ICL 3300 Advanced Graphics Workstation) was developed by ICL as a replacement for the PERQ 2. The PERQ 3A had an all-new hardware architecture based around a 12.5&nbsp;MHz [[Motorola]] [[Motorola 68020|68020]] [[microprocessor]], [[Motorola 68881|68881]] [[floating-point unit]] and 68450 Direct Memory Access Controller, plus two [[AMD 29000|AMD 29116A]] [[32-bit]] [[bit slice]] processors which acted as graphics co-processors. It also had up to 2 MB of RAM, a [[SCSI]] hard disk and was housed in a desktop "mini-tower"-style enclosure. The operating system was a port of [[UNIX System V]] Release 2 called PNX 300.{{citation needed|date=August 2010}} Prototype units were produced in 1985, but the project was cancelled before full production commenced (the project had run late and ICL decided it was a solution provider - it would sell Sun workstations as part of the solution).{{citation needed|date=August 2010}}

Another workstation design under development at the time of the company's demise, the ''PERQ 3B'' was a colour model (sometimes referred to as the ''PERQ 5'') was taken over by [[Crosfield Electronics]] for its Crosfield Studio 9500 [[page layout]] workstation.<ref name="faq"/> The workstation was also known internally as Python, was developed in 1986 jointly by MegaScan and Conner Scelza Associates (both in [[Gibsonia, Pennsylvania|Gibsonia, PA]], U.S.A.) and the Crosfield team (in [[Hemel Hempstead]], England). MegaScan, led by Brian Rosen, developed the workstation electronics and Conner Scelza Associates (led by Jerry Conner and Don Scelza) ported UNIX and wrote all the other supporting software. Crosfield (led by Andrew Chapman) were the overall project managers and had embedded engineers in MegaScan (Simon Butler and Mark Somervail) and Conner Scelza (Roger Willcocks).<ref>[http://bitsavers.informatik.uni-stuttgart.de/pdf/perq/RD_Davis/Davis-PERQ_Workstations_Nov03.pdf PERQ Workstations by R. D. Davis]</ref>

The Crosfield requirement was for a very high performance graphics system (known as Viper, developed by their subsidiary benchMark Technologies) and a large (at the time) amount of disk storage. The Crosfield team in Hemel Hempstead developed an early [[RAID]] solution that supported up to 8 [[SCSI]] controllers operating in parallel with data streaming from 5¼-inch [[full-height]] drives and a fast [[fibre-optic]] network known as GALAN. Prototypes were running in late 1986 in both the US and UK and volume production from Crosfield's [[Peterborough]] factory started early 1987.<ref>[http://www.caffnib.co.uk/xfld_gloss.html A Crosfield Glossary]</ref>

===Peripherals===
Various optional OIO boards were produced for the PERQ 1 and 2: 3RCC OIO boards provided a 16-bit parallel PERQlink interface (intended for downloading microcode from another PERQ at boot time) plus Ethernet or a [[Canon Inc.|Canon]] CX [[laser printer]] controller. Thus, a PERQ 2 could be configured with two Ethernet ports (EIO plus OIO). A [[dot-matrix printer]] could also be connected to the RS-232 or IEEE-488 ports. Other third-party OIO boards were produced to interface to other devices, such as [[Quarter-inch cartridge|QIC]]-02 [[tape drive]]s or [[video camera]]s.<ref name="hardware-faq"/>

==Software==

The PERQ's original [[P-code machine#UCSD p-Machine|p-Code]]-like instruction set (called ''Q-Code'') was optimized for [[Pascal (programming language)|Pascal]] (specifically, an extended PERQ Pascal). Q-Code instructions could be executed at a rate of up to 1 [[million instructions per second]].<ref>[http://www.chilton-computing.org.uk/acd/sus/perq_pr/p007.htm PERQ Publicity: ICL's PERQ Brochure], Chilton Computing, UK.</ref> This gave rise to the alternative definition of the PERQ name: ''Pascal Evaluation Real Quick''. In fact it was generally more efficient to use Pascal than to attempt to create "[[assembly language]]" programs directly with Q-Code.{{Citation needed|date=June 2009}}

===Operating systems===
A variety of [[operating system]]s were developed for the PERQ. These included:<ref name="faq"/>

;POS (PERQ Operating System): The initial single-task operating system for PERQ workstations, developed by 3RCC. POS and its utilities were written in PERQ Pascal.

;MPOS (Multitasking POS): A [[Computer multitasking|multitasking]] version of POS, not officially released by 3RCC.

;[[Accent kernel|Accent]]: A multitasking research operating system developed at CMU, with a [[window manager]] called Sapphire. Accent was a predecessor of the [[Mach kernel]] which many later operating systems would use. A [[UNIX System V]]-compatible environment running under Accent in a Sapphire window, called ''QNIX'', was developed by [[Spider Systems]].

;PNX ({{IPAc-en|'|p|i:|n|ɪ|k|s}}  {{respell|PEE|nix}}): A port of [[Unix]] for the PERQ, based on [[Seventh Edition Unix]] and [[UNIX System III]]. This was developed by ICL at [[Bracknell]], [[Dalkeith Palace]] and later [[Kidsgrove|Kidsgrove (Staffordshire)]] for the UK research community.<ref name="faq"/> PNX used its own microcode, more appropriate for the [[C (programming language)|C programming language]], called ''C-Code''.

;[[Flex machine|FLEX]]:  Developed by the [[Royal Signals and Radar Establishment]], FLEX was implemented in microcode and similar to other early workstation systems such as [[Lisp machine]]s, [[UCSD Pascal]] or [[Modula-2]], except that the language of choice was [[ALGOL 68]].

=== Compilers ===

ICL and 3RCC contracted with the [[Edinburgh Regional Computing Center]] (ERCC) over 1981-1982 to supply an optimised [[Fortran#FORTRAN_77|Fortran77]] compiler.  This also resulted in an [[Edinburgh_IMP|Imp]] compiler being created, as the F77 compiler from the ERCC was written in Imp.  The ERCC compilers generated [[Q-Code]].  By 1987, maintenance of the PERQ compiler suite had been taken over by a commercial spin-off group of ex-ERCC employees, [[Edinburgh Portable Compilers|Edinburgh Portable Compilers Ltd]] (EPCL).

===Applications===
[[File:Spy text editor running on a PERQ workstation.jpg|thumb|150px|right|''Spy'' third party [[text editor]] from 1983 running on a PERQ workstation at Bletchley Park in 2013.]]
The PERQ was a popular early graphical workstation; therefore, it helped spawn many early third-party applications that took advantage of the [[graphical user interface]] and [[raster graphics|bitmapped graphics]]. [[Intran]] (around 1982) produced a pioneering graphical program suite called MetaForm, which consisted of the separate Graphics Builder, Font Builder, Form Builder, and File Manager programs. The PERQ also served as a dedicated platform for several pioneering [[hypertext]] programs, such as [[ZOG (hypertext)|ZOG]], [[KMS (hypertext)|KMS]], and [[Guide (hypertext)|Guide]]. DP ("Drawing Program"), a [[Computer-aided design|CAD]] system used for creating [[circuit diagram]]s on the PERQ, was written by Dario Giuse at CMU.<ref>{{Cite web |url=http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA126401 |title=Entry for ''DP - Command Set'' at the  Defense Technical Information Center |access-date=2008-12-03 |archive-url=https://web.archive.org/web/20090531004614/http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA126401 |archive-date=2009-05-31 |url-status=dead }}</ref>

==References==
{{Reflist|2}}

== External links ==
* [https://www.fujitsu.com/ie/imagesgig5/ICL-Technical-Journal-v03i02.pdf ICL Technical Journal - November 1982]
* [http://www.chiark.greenend.org.uk/~pmaydell/PERQ/ All About PERQ Workstations]
* [http://www.digibarn.com/collections/systems/perqt2/ DigiBarn: The Three Rivers PERQ]
* [http://bitsavers.org/pdf/perq PERQ Documentation at bitsavers.org]
* [http://toastytech.com/guis/perq.html Graphical User Interface Gallery: Three Rivers / ICL Perq]
* [http://www.chilton-computing.org.uk/acd/sus/overview.htm Rutherford Laboratory Atlas Computing Division: Single User System Programme archive]. Includes detailed material relating to PERQ history as it affected a joint project involving the Science and Engineering Research Council and ICL.
* [https://web.archive.org/web/20090715073249/http://yahozna.dyndns.org/projects/PERQemu/index.html PERQemu: a PERQ 1 emulator] for Microsoft Windows/Mono (under development, v0.21 is capable of booting and running POS)
* [https://github.com/jdersch/PERQemu/blob/master/PERQemu/Readme.txt PERQemu: a PERQ 1 emulator] for Microsoft Windows/Mono (under development, v0.4.4 is the fourth major release)
* [https://groups.google.com/g/alt.sys.perq/c/Svlt7pabvns ICL Perq 3A major component lists]
* [https://history.dcs.ed.ac.uk/archive/os/emas/users/ercs07/emas-2900/oldqfiles_f77code2.txt Code generator for F77 and Imp compilers] by Edinburgh Regional Computing Center (ERCC). (The full compiler sources are in the [https://history.dcs.ed.ac.uk/archive/os/emas/users/ercs07/emas-2900/ enclosing directory].  Some related [https://history.dcs.ed.ac.uk/archive/os/emas/users/ercs07/emas-2900/COPYRIGHT.LIST explicitly copyrighted files] have been removed from that public archive.)

{{ICL hardware}}

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