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Unformatted text preview: ) + Fraction enhanced Speedupenhanced Best you could ever hope to do:
Speedupmaximum = Some material is adapted from D. Culler & D. Patterson (UCB) 1
(1 - Fractionenhanced ) enhanced S. Ziavras Amdahl
Amdahl’s Law example
• New CPU 10X faster
• I/O bound server, so 60% time waiting for I/O
Speedup overall = 1 (1 − Fraction enhanced Fraction
)+
Speedup enhanced
enhanced 1 1
=
=
= 1 . 56
0 . 64
(1 − 0.4 ) + 0.4
10 • Apparently, its human nature to be attracted by
10X faster, vs. keeping in perspective it’s just
~1
~1.6X faster
Some material is adapted from D. Culler & D. Patterson (UCB) S. Ziavras 5) Processor performance equation
inst count
CPU time = Seconds
Program Program = Instructions x
Program Inst Count
X Cycles Compiler X
X Cycle f (X) Inst. Set. Cycle time x Seconds Instruction CPI CPI X Organization
Technology
Some material is adapted from D. Culler & D. Patterson (UCB) X X
X
S. Ziavras What
What’s a Clock Cycle?
Latch
or
register combinational
logic • Old days: several levels of gates
• Today: determined by...
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- Fall '09
- Computer Architecture, Central processing unit, Machine code, D. Culler, D. Patterson
-
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