Question

Suppose that we are developing a new version of the AMD Barcelona processor with a 4 GHz clock rate. We have added some additional instructions to the instruction set in such a way that the number of instructions has been reduced by 15%. The execution time is reduced to 700 s. Find the new CPI.

Answer 1

Question:

Barcelona has an instruction count of 2.389E12, an execution time of 750 s, and a  reference time of 9650 s.

Answer:

New CPI is 1.379

Explanation:

Given:

Clock Rate=4 GHz

Reduction in number of instructions=15%

Execution time=700 sec

Instruction Count=$2.389*10^{12}$

Find:

New CPI=?

Solution:

Cycle Time=1/Clock Rate

$Cycle\ Time= 0.25*10^{-9} sec$

Execution Time= Clock cycles * Cycle Time

Clock Cycles=Execution Time/Cycle Time

$Clock Cycles=\frac{700}{0.25*10^{-9}}$

$Clock\ Cycles= 2.8*10^{12}$

New Instruction Count=$2.389*10^{12}$*0.85

New Instruction Count=$2.03*10^{12}$

$CPI=\frac{Clock\ Cycles}{New\ Instructions} \\CPI=\frac{2.8*10^{12}}{2.03*10^{12}} \\CPI= 1.379$

New CPI is 1.379