Performance

Performance Equation

$$\text{CPU Time} = \text{Instruction Count}\times \text{CPI} \times \text{Clock Cycle Time}$$

Here:

• CPI - Cycles Per Instruction
  $\text{CPI} = \text{Total CPU cycles} / \text{Instruction count}$
• IPC Instructions Per Cycle
  $\text{IPC} = 1 / \text{CPI}$

Performance can be improved by:

• Reducing instruction count (better compiler)
• Lowering CPI (efficient microarchitecture)
• Reducing clock cycle time (faster hardware)

Performance Measurement and Benchmarking

• Compare processors using different kinds of benchmarks.
• Performance is domain-specific.
• Requirements evolve over time and depend on target devices.