Information Technology Reference
In-Depth Information
No. of
instructions
(in millions)
No. of
cycles per
instruction
Instruction
category
Machine (A)
ALU
8
1
Load & store
4
3
Branch
2
4
Others
4
3
Machine (B)
ALU
10
1
Load & store
8
2
Branch
2
4
Others
4
3
P
i
¼
1
CPI
i
I
i
(8
1
þ
4
3
þ
4
3
þ
2
4)
10
6
(8
CPI
a
¼
Instruction count
¼
2
:
2
þ
4
þ
4
þ
2)
10
6
10
6
Clock rate
CPI
a
200
MIPS
a
¼
10
6
¼
10
6
90
:
9
:
2
2
10
6
Instruction count
CPI
a
Clock rate
18
2
:
2
CPU
a
¼
¼
¼
0
:
198 s
200
10
6
P
i
¼
1
CPI
i
I
i
10
6
(10
1
þ
8
2
þ
4
4
þ
2
4)
CPI
b
¼
Instruction count
¼
¼
2
:
1
(10
þ
8
þ
4
þ
2)
10
6
10
6
Clock rate
CPI
a
200
MIPS
b
¼
10
6
¼
10
6
¼
95
:
2
2
:
1
10
6
Instruction count
CPI
a
Clock rate
20
2
:
1
CPU
b
¼
¼
¼
0
:
21 s
200
10
6
MIPS
b
.
MIPS
a
and
CPU
b
.
CPU
a
The example shows that although machine B has a higher MIPS compared to
machine A, it requires longer CPU time to execute the same set of benchmark
programs.
Million floating-point instructions per second, MFLOP (rate of floating-point
instruction execution per unit time) has also been used as a measure for machines'
performance. It is defined as
Number of floating-point operations in a program
Execution time
MFLOPS
¼
10
6
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