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Consider a 5 stage instruction pipeline having latencies (in ns) 1, 2, 3, 4 and 5 respectively.
Find average CPI of non-pipeline CPU when speed up achieved with respect to pipeline is 4
(assume ideal case for pipelining)?
(a) 1.23
(c) 1.66
(b) 1.33
(d) 1.73
asked in CO & Architecture by Junior (653 points)
retagged by | 74 views
b) 1.33???
yes,can you just help to get it with proper formula and its explanation,Thanks :)

1 Answer

+4 votes
Best answer

Tnon-pipeline = sum of all stages delay = 15ns

Tpipeline  = max delay among all stages delay = 5ns

Given speedup = 4

Speedup = $\frac{\text{Execution of non pipeline}}{\text{Execution of pipeline}}$

Execution of non pipelined = CPInon-pipelined * Cycle time

Execution of non pipelined = CPInon-pipelined * 15ns

Now,

Execution of pipelined = CPIpipelined * cycle time 

In pipelined ideally CPIpipelined = 1

Execution of pipelined = 1 * 5ns

4 = (CPInon-pipelined *15)/(1*5)

CPInon-pipelined = 4/3

CPInon-pipelined = 1.33

Ans = 1.33

answered by Veteran (11.3k points)
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