Editing PERQ (section)

==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"/>