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We have two implementations of the same Instruction Set Architecture (ISA). Machine $A$ has a clock cycle time of $50$ ns and a CPI of $4.0$ for a program, while machine $B$ has a clock cycle of $65$ ns and a CPI of $2.5$ for the same program.

Which of the following is TRUE?

1. Machine A is faster than B.
2. Machine B is faster than A.
3. Both have the same speed.
4. None of the above

As we know cpu time = [Instruction Count ( IC) * CPI * Clock time] ,
for M/c A cpu time is = IC*4.0 * 50 = 200 IC ns ,

for M/c B cpu time = 162.5 IC ns  ,

as ISA is same for both then IC is equal for both,

M/c A takes much time ( longer cpu time ) to perform same program than M/c B , hence M/c B is faster.
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