02 Computer-Evolution
02 Computer-Evolution
02 Computer-Evolution
Others 800 4
• Conclusions
— f small, parallel processors has little effect
— N ->∞, speedup bound by 1/(1 – f)
– Diminishing returns for using more processors
Example3
Considering Example1, assume that the program can be
executed in eight parallel tasks or threads with roughly equal
number of instructions executed in each task. Execution is on
an 8-core system with each core (processor) having the same
performance as the single processor originally used.
Coordination and synchronization between the parts adds an
extra 25,000 instruction executions to each task.
a. Determine the average CPI.
b. Determine the corresponding MIPS rate.
c. Calculate the speedup factor.
Solution for Example 3
Assuming the same instruction mix means
that the additional instructions for each task
should be allocated proportionally among
the instruction types.
So we have the following table: