Question 1.7 of Computer Architecture a quntitative approach, third edition a ce
ID: 3665614 • Letter: Q
Question
Question 1.7 of Computer Architecture a quntitative approach, third edition
a certain benchmark contains 195,578 floating-point operations with the detail shown in figure
Operation
Operation Count
Add 82,014
Subtract 8,229
Multiply 73,220
Divide 21,399
Convert integer to FP 6,006
Compare 4,710
Total 195,578
the benchmark was run on an embedded processor after compilation with optimization turned on. the embedded processor is based on a current RISC processor that includes floating point for reasons of cost, power consumption, and lack of need for floating point by the target applications. the compiler allows floating point instructions to be calculated with the hardware units or using software routines depending on compiler flags. the benchmark took 1.08 seconds on the RISC processor and 13.6 seconds using software or its embedded version. assume that the CPI using the RISC processor was measured to be 10, while the CPI of the embedded version of the processor was measured to be 6.
a. [15] <1.9> What is the total number of instructions executed for both runs
b. [15] <1.9> What is the MIPS rating for both runs?
c. [8] <1.9> On the average, how many integer instructions does it take to perform a floating-point operation in software?
Operation Count
Add 82,014
Subtract 8,229
Multiply 73,220
Divide 21,399
Convert integer to FP 6,006
Compare 4,710
Total 195,578
Explanation / Answer
a)What is the total number of instructions executed for both runs
Total instructions executed by RISC processor is 195578.
Let calculate the excutuion time by using T,CT Formula
T be execution time.
I is number of instructions
CPI average clock per instruction
CT cycle time.
T= I * CPI * CT
CT= T / I * CPI = 1.08 / (195578*10)
Using CPI and T values for the embedded processor and assuming that the cycle time is the same for both RISC and embedded processors:
=>13.6= I * 6 * CT
=>I= 13.6 / (6 * CT)
I = 13.6 * 10 * 195578 / 6 * 1.08
= 4104723 executed instructions by the embedded processor.
b) What is the MIPS rating for both runs?
MIPS RISC= 195578 / (1000000 * 1.08) = 0.18
Embedded MIPS = 4104723 / 1000000 * 13.6 = 0.30
c) On the average, how many integer instructions does it take to perform a floating-point operation in software?
On the average Average number of integer instructions it takes to perform a floating point operation:
(4104723)/(195578) = 20.99
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