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The Distributed Array Processor (DAP) produced by
International Computers Limited International Computers Limited (ICL) was a British computer hardware, computer software and computer services company that operated from 1968 until 2002. It was formed through a merger of International Computers and Tabulators (ICT), English Ele ...
(ICL) was the world's first commercial
massively parallel computer Massively parallel is the term for using a large number of computer processors (or separate computers) to simultaneously perform a set of coordinated computations in parallel. GPUs are massively parallel architecture with tens of thousands of t ...
. The original paper study was complete in 1972 and building of the prototype began in 1974. The first machine was delivered to
Queen Mary College Queen Mary University of London (QMUL, or informally QM, and formerly Queen Mary and Westfield College) is a public research university in Mile End, East London, England. It is a member institution of the federal University of London. Today, ...
in 1979.


Development

The initial Pilot DAP was designed and implemented by Dr Stewart F Reddaway with the aid of David J Hunt and Peter M Flanders at the ICL Stevenage Labs. Their manager and a major contributor was John K Iliffe, designer of the Basic Language Machine and known for
Iliffe vector In computer programming, an Iliffe vector, also known as a display, is a data structure used to implement multi-dimensional array data structure, arrays. Data structure An Iliffe vector for an ''n''-dimensional array (where ''n'' ≥ 2) ...
s. The pilot implementation had a 32×32 processing element arrangement. The ICL DAP had 64×64 single bit
processing element This glossary of computer hardware terms is a list of definitions of terms and concepts related to computer hardware, i.e. the physical and structural components of computers, architectural issues, and peripheral devices. A ...
s (PEs) with 4096 bits of storage per PE. It was attached to an ICL mainframe and its memory was mapped into the mainframe's memory. Programs for the DAP were written in DAP FORTRAN which was FORTRAN extended with 64×64 matrix and 64 element vector primitives. DAP Fortran compiled to an
assembly language In computing, assembly language (alternatively assembler language or symbolic machine code), often referred to simply as assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence bet ...
called APAL (Array Processor Assembly Language). The DAP had a
single instruction, multiple data Single instruction, multiple data (SIMD) is a type of parallel computer, parallel processing in Flynn's taxonomy. SIMD describes computers with multiple processing elements that perform the same operation on multiple data points simultaneousl ...
(SIMD) architecture. Each operation could be performed under the control of a mask which controlled which elements were affected. Array programs were executed as
subroutines In computer programming, a function (also procedure, method, subroutine, routine, or subprogram) is a callable unit of software logic that has a well-defined interface and behavior and can be invoked multiple times. Callable units provide a p ...
of normal mainframe FORTRAN programs and IO was handled by the mainframe. Operationally, there was an overhead to transfer computational data into and out of the array, and problems which did not fit the 64×64 matrix imposed additional complexity to handle the boundaries (65×65 was perhaps the worst case!)—but for problems which suited the architecture, it could outperform the current
Cray Cray Inc., a subsidiary of Hewlett Packard Enterprise, is an American supercomputer manufacturer headquartered in Seattle, Washington. It also manufactures systems for data storage and analytics. Several Cray supercomputer systems are listed ...
pipeline architectures by two orders of magnitude. The ICL 2980 was not a popular machine and this held back the use of the DAP as an attached processor was restricted initially to this one range. The design as described in Reddaway's 1973 paper is pretty much that which was implemented in the first commercial version except the facility to supply address bits from the processing elements was removed. This change greatly simplified hardware error detection. A notable extra facility was carry propagation to simplify vector mode addition.


After ICL

The DAP Pwas sold off to a
venture capital Venture capital (VC) is a form of private equity financing provided by firms or funds to start-up company, startup, early-stage, and emerging companies, that have been deemed to have high growth potential or that have demonstrated high growth in ...
-funded
start-up A startup or start-up is a company or project undertaken by an entrepreneur to seek, develop, and validate a scalable business model. While entrepreneurship includes all new businesses including self-employment and businesses that do not intend ...
company Active Memory Technology (AMT) which was then taken over by
Cambridge Parallel Processors Cambridge ( ) is a city and non-metropolitan district in the county of Cambridgeshire, England. It is the county town of Cambridgeshire and is located on the River Cam, north of London. As of the 2021 United Kingdom census, the population of t ...
(CPP). It was enhanced and made smaller and faster as the Gamma series. An 8-bit processor with some local 8-bit wide memory was added to the processor and fast IO capabilities were implemented. It could be programmed in either C++ or Fortran-Plus. These were more flexible than DAP FORTRAN, in particular they automatically took care of choosing a mapping from user specified matrix and vector bounds to the underlying hardware. Sample DAPs are in storage at the
Computer History Museum The Computer History Museum (CHM) is a computer museum in Mountain View, California. The museum presents stories and artifacts of Silicon Valley and the Information Age, and explores the Digital Revolution, computing revolution and its impact ...
. CPP ceased trading in 2004.


Mini-DAP and Mil-DAP

A smaller 32x32 version was created between 1984 and 1987. The commercial version was called the Mini-DAP, normally attached to a
PERQ 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 ...
system (so was sometimes called the PERQ-DAP), and the ruggedised military version was called the Mil-DAP.


See also

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Connection Machine The Connection Machine (CM) is a member of a series of massively parallel supercomputers sold by Thinking Machines Corporation. The idea for the Connection Machine grew out of doctoral research on alternatives to the traditional von Neumann arch ...
*
Goodyear MPP The Goodyear Massively Parallel Processor (MPP) was a massively parallel processing supercomputer built by Goodyear Aerospace for the NASA Goddard Space Flight Center. It was designed to deliver enormous computational power at lower cost than ot ...
*
MasPar MasPar Computer Corporation (later NeoVista Software, Inc.) was a minisupercomputer vendor that was founded in 1987 by Jeff Kalb. The company was based in Sunnyvale, California. History While Kalb was the vice-president of the division of Digita ...
*
Parsytec Isra Vision Parsytec AG, a subsidiary of Isra Vision, was originally founded in 1985 as Parsytec (''parallel system technology'') in Aachen, Germany. Parsytec gained recognition in the late 1980s and early 1990s as a manufacturer of transputer- ...
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SUPRENUM SUPRENUM (, ) was a German research project to develop a parallel computer from 1985 through 1990. It was a major effort which was aimed at developing a national expertise in massively parallel processing both at hardware and at software level. A ...


References


External links

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DAP personal history


{{DEFAULTSORT:Icl Distributed Array Processor DAP Massively parallel computers DAP