Parallel Processor Architectures: Identifying the Non-Architecture
Parallel computers are often classified by the number of instruction streams and data streams they support, following a taxonomy commonly attributed to Flynn (e.g., SISD, SIMD, MISD, MIMD). In that classification, keyword instruction/data-stream classification is the key idea. keyword SISD, keyword SIMD, and keyword MIMD are standard categories.
In contrast, “SISO” is not a standard named parallel processor architecture category in the common instruction/data-stream taxonomy; it’s typically not presented alongside SISD/SIMD/MISD/MIMD in standard treatments of parallel architecture classification. Therefore, among the options:
- a) SIMD ✅ is a known parallel category
- b) MIMD ✅ is a known parallel category
- d) Multi-core ✅ is a common parallel hardware organization used to run multiple threads/cores concurrently
- c) SISO ❌ is the “NOT” choice as a recognized parallel processor architecture type in the standard taxonomy
This means the correct answer is: (c) SISO.
Key point: SIMD and MIMD are standard instruction/data-stream parallel categories; multi-core is a parallel hardware strategy. “SISO” is not a canonical parallel processor architecture type in the commonly taught classification.
Tip: Use the classification vocabulary
When MCQs ask for the “architecture type,” look for terms that match the standard instruction/data-stream taxonomy (SISD/SIMD/MISD/MIMD). If a term isn’t part of that set, it’s often the distractor.
To reason confidently, connect each option to the underlying idea of how parallelism is exposed:
- keyword SIMD: one control/instruction stream, many data elements processed in lockstep.
- keyword MIMD: multiple instruction streams execute concurrently on different data.
- keyword Multi-core: multiple cores enable concurrent execution (often supporting shared memory and thread-level parallelism).
- keyword SISO: not a widely used canonical category in the standard parallel architecture naming scheme (unlike SIMD/MIMD).
MCQ Elimination Method for Parallel Architecture Questions
- 1Step 1
If the question uses names like SIMD and MIMD, it’s likely referring to the instruction/data-stream classification (Flynn-style).
- 2Step 2
SIMD and MIMD are standard named categories in this taxonomy, so they cannot be the “NOT” answer.
- 3Step 3
Multi-core is not a Flynn taxonomy label like SIMD/MIMD, but it is a standard parallel hardware organization used for concurrent execution, so it is still a plausible “parallel architecture” option in typical exams.
- 4Step 4
If the remaining term (here, SISO) is not a canonical parallel architecture category in the standard taxonomy, it is the best candidate for “NOT”.
- 5Step 5
Choose c) SISO.
Common Parallelism Concept Map (How Terms Relate)
Instruction vs. Data Streams
Classification focusNames like SISD/SIMD/MISD/MIMD emphasize the relationship between instruction streams and data streams."
SIMD
Data-parallel modeOne instruction stream operating on many data items."
MIMD
General concurrent executionMany instruction streams operating concurrently on multiple data sets."
Multi-core
Hardware realizationMultiple cores enabling parallel execution (often thread-level)."
SISO
MismatchNot a canonical named category in the common instruction/data-stream parallel architecture sets."
Visual summary of why “SISO” is the distractor
| Option | Category/Meaning (typical meaning in parallel computing) | Standard named architecture? | Verdict |
|---|---|---|---|
| SIMD | Single Instruction, Multiple Data | Yes | Keep |
| MIMD | Multiple Instruction, Multiple Data | Yes | Keep |
| SISO | Not a canonical term in the standard Flynn-style instruction/data-stream set | No | Remove |
| Multi-core | Multi-CPU-core hardware enabling concurrent execution | Yes (hardware organization) | Keep |
Frequently Asked Nuances (Exam-Relevant)
Knowledge Check
Which of the following is NOT a type of parallel processor architecture?