Parallel Architectures

1
Parallel Architectures
2
Overview

• This paper is a rehash of a paper that appeared
  in 1972
• Some Computer Organizations and Their
  Effectiveness. IEEE Transactions on Computers,
  C-21(9)948-960, September 1972.
• Four basic parallel computer taxonomies
• SISD
• SIMD
• MISD
• MIMD
• Each has its purpose

3
SISD

• Single Instruction Single Data sequential
  (unless you consider the micro-code level)
• Pentium (of old)
• VAX
• SGI
• Your stereo-typical Von Neumann machines

4
SIMD

• Single Instruction Multiple Data data level
  parallelism
• All PEs do the same operations synchronously on
  their own separate data
• Connection Machine CM-1, CM-2
• IUA CAAPP level
• Vector processor within SISD machines such as the
  Cray

5
MISD

• Multiple Instruction Single Data dataflow
  parallelism
• Systolic array
• Pipeline machines
• Not talked about all that much

6
MIMD

• Multiple Instruction Multiple Data
  control/process level parallelism
• Cosmic Cube
• Connection Machine CM-5
• IUA ICAP level

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SPMD

• Single Program Multiple Data data and control
  level parallelism
• Can be sub-classed from either SIMD or MIMD
• PEs have identical programs but separate program
  counters (asynchronous SIMD)

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Interesting Bits

• Claims that SIMD is of limited application
• I think this is unfair but maybe closer to the
  truth than what Thinking Machines, Inc. was
  pushing
• networking commodity workstations through a
  local area network as a MIMD architecture
• SETI started in 1984 which was prior to
  publication I imagine he did not have such a
  statement in the 1972 paper
• However, we cannot expect that the ease of
  programming these improved configurations will
  advance few of which are foreseeable.
• He speaks from experience and common sense

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End Notes

• Four basic parallel computer taxonomies
• SISD
• SIMD
• MISD
• MIMD
• Each has its purpose
• If someone builds/sells only 1 type, they will
  try to convince you that you dont need the rest,
  no matter which type they build/sell