Distributed Array Processor
Encyclopedia
The Distributed Array Processor (DAP) produced by
International Computers Limited (ICL) was the world's first commercial
massively parallel computer. 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
in 1979.
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 who had designed the Basic Language Machine - he is better known nowadays for Iliffe vector
s.
The ICL DAP had 64x64 single bit processing elements (PEs) with 4096
bits of storage per PE. It was attached to an ICL mainframe and
could be used as normal memory. Programs for the DAP were written
in DAP FORTRAN
which was FORTRAN
extended with 64x64 matrix and
64 element vector primitives. It had a Single Instruction Multiple Data
(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 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 64x64 matrix imposed additional complexity to handle the boundaries (65x65 was perhaps the worst case!) – but for problems which suited the architecture, it could outperform the current Cray
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 Stewart'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.
The DAP was later hived off as a separate company Active Memory Technology
(AMT) which was then taken over by Cambridge Parallel Processors (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
.
CPP ceased trading in 2004.
system (so was sometimes called the PERQ-DAP), and the ruggedised military version was called the Mil-DAP.
International Computers Limited (ICL) was the world's first commercial
massively parallel computer. 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
Queen Mary, University of London is a public research university located in London, United Kingdom and a constituent college of the federal University of London...
in 1979.
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 who had designed the Basic Language Machine - he is better known nowadays for Iliffe vector
Iliffe vector
In computer programming, an Iliffe vector, also known as a display, is a data structure used to implement multi-dimensional arrays. An Iliffe vector for an n-dimensional array consists of a vector of pointers to an -dimensional array...
s.
The ICL DAP had 64x64 single bit processing elements (PEs) with 4096
bits of storage per PE. It was attached to an ICL mainframe and
could be used as normal memory. Programs for the DAP were written
in DAP FORTRAN
DAP FORTRAN
DAP FORTRAN was an extension of the non IO parts of FORTRAN with constructs that supported parallel computing for theICL Distributed Array Processor...
which was FORTRAN
Fortran
Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
extended with 64x64 matrix and
64 element vector primitives. It had a Single Instruction Multiple Data
(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 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 64x64 matrix imposed additional complexity to handle the boundaries (65x65 was perhaps the worst case!) – but for problems which suited the architecture, it could outperform the current Cray
Cray
Cray Inc. is an American supercomputer manufacturer based in Seattle, Washington. The company's predecessor, Cray Research, Inc. , was founded in 1972 by computer designer Seymour Cray. Seymour Cray went on to form the spin-off Cray Computer Corporation , in 1989, which went bankrupt in 1995,...
pipeline architectures by two orders of magnitude. The ICL 2980
ICL 2900 Series
The ICL 2900 Series was a range of mainframe computer systems announced by the UK manufacturer ICL on 9 October 1974. The company had started development, under the name "New Range" immediately on its formation in 1968...
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 Stewart'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.
The DAP was later hived off as a separate company Active Memory Technology
(AMT) which was then taken over by Cambridge Parallel Processors (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++
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
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
Computer History Museum
The Computer History Museum is a museum established in 1996 in Mountain View, California, USA. The Museum is dedicated to preserving and presenting the stories and artifacts of the information age, and exploring the computing revolution and its impact on our lives.-History:The museum's origins...
.
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 PERQPERQ
The PERQ, also referred to as the Three Rivers PERQ or ICL PERQ, was a pioneering workstation computer produced in the early 1980s....
system (so was sometimes called the PERQ-DAP), and the ruggedised military version was called the Mil-DAP.
See also
- Goodyear MPPGoodyear MPPThe Goodyear Massively Parallel Processor was amassively parallel processing supercomputer built by Goodyear Aerospacefor the NASA Goddard Space Flight Center.It was designed to deliver enormous computational power at lower cost than...
- Thinking Machines Connection MachineConnection MachineThe Connection Machine was a series of supercomputers that grew out of Danny Hillis' research in the early 1980s at MIT on alternatives to the traditional von Neumann architecture of computation...
- MasParMasParMasPar Computer Corporation was a minisupercomputer vendor that was founded in 1987 by Jeff Kalb. The company was based in Sunnyvale, California....