1. Parallel Architectures
04/04/2007

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): , September 1972.
Four basic parallel computer taxonomies
SISD
SIMD
MISD
MIMD
Each has it’s purpose
04/04/2007

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
Controller PE
Fetch/Decode/Execute
04/04/2007

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
Fetch/Decode
Controller PE
Execute
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5. MISD Multiple Instruction Single Data – dataflow parallelism
Systolic array
Pipeline machines
Not talked about all that much
Controller PE
Fetch/Decode/Execute
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6. MIMD
Multiple Instruction Multiple Data – control/process level parallelism
Cosmic Cube
Connection Machine CM-5
IUA ICAP level
Controller PE
Fetch/Decode/Execute
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7. 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)
Fetch
Controller PE
Decode/Execute
04/04/2007

8. 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
04/04/2007

9. End Notes Four basic parallel computer taxonomies
SISD
SIMD
MISD
MIMD
Each has it’s purpose
If someone builds/sells only 1 type, they will try to convince you that you don’t need the rest, no matter which type they build/sell
04/04/2007