Flynn's Taxonomy

Question 1

How can you improve the performance of a SISD machine?

Answer 1

Increase Clock speed

• Reduce critical path delay
• -Remove complex hardware with large critical path delay (dividers)
• -Improve implementation technology (decrease transistor size / distance to reduce delay between them)
• • Will require / exhaust more power, extra cooling etc.

Question 2

Explain the advantages / disadvantages of SIMD

Answer 2

Increases concurrency:

Instructions do the same operation to multiple fetched data values at a time

Disadvantage:
- Only works for applications which can be written to take advantage (do lots of the same operation already) Reverts to SISD otherwise, waistline performance

• Extra hardware (adders, muxes, routing from registers/memory)

Question 3

Explain what a MISD CPU does

Answer 3

Splits instructions into multiple sub-instructions/stages (pipelining)

Multiple Instructions overlap in fetch / decode /execute

(If pipeline is full, (each stage busy) one instruction will end every clock cycle)

Question 4

How can a MISD processor improve performance?

Answer 4

By breaking stages into smaller ones, less complex hardware circuits are required, lowering critical path delay and increasing clock speed (more instructions per sec)

Question 5

Disadvantages of MISD?

Answer 5

Higher clock speed = more power dissipation

Due to concurrency/parallelism, data hazards occur

Question 6

What is MIMD?

Answer 6

Multiple processors (physically joined or separate) which work together towards a common goal.

Passing data between each other with shared bus/communication network

Question 7

Disadvantages of MIMD

Answer 7

Long time spent communicating / syncing memory access

Not all algorithms can work on this architecture (sequential etc)