lec03 - LECTURE - 03 Amdahl's Law Amdahl's law: Diminishing...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: LECTURE - 03 Amdahl's Law Amdahl's law: Diminishing returns Limit on overall speedup 1-F F 1-F F/Speedup Corollary: make the common case fast Overallspeedup 1 F F 1 F F Speedup Illustrating Amdahl's Law Example: implement cache, or faster ALU? Cache improves performance by 10x ALU improves performance by 3x Depends on fraction of instructions Suppose F mem 0.2, F alu 0.5, F other 0.3 Speedupwithcache 1 0.8 0.2 10 1.22 Speedupwith faster ALU 1 0.5 0.5 3 1.5 Example continued... Fixing for what value of is adding a cache better? F alu 0.5 F mem 1 1 F mem F mem 10 1.5 F mem 10 27 0.36 The CPU Performance Equation CPUtime Num.clockcycles Clockcycletime CPUtime Num.of clockcycles Clockrate OR CPUtime IC CPI Cycletime Putting these together Num.of clockcycles InstructionCount CyclesPerInstruction IC CPI For a program, More on the Equation This form is convenient Involves many relevant parameters Remembering is easy CPUtime Seconds Program Seconds Clockcycle Clockcycles Instruction Instructions Program With CPI as the independent variable CPI CPUtime Clockcycletime IC Other Convenient Forms of the...
View Full Document

Page1 / 16

lec03 - LECTURE - 03 Amdahl's Law Amdahl's law: Diminishing...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online