Processor Performance

Power Consumption

• Power: an instantaneous measurement (Watts)
  • Desktop: 100W
  • Laptop: 25W
  • Phone: 1-2W
• Energy: Total Capacity

Benchmark Types

1. Real - typical user application
2. Kernel - Loop/function takes out of a real application
3. Toy - puzzle/game
4. Synthetic - not a real program, tests a particular functionality

SPEC CPU Benchmark

• Set of integer programs
• Set of floating point programs (scientific applications)
• updated every few years

Amdhl's Law

Definition

Formula that gives the theoretical speedup in latency of the execution of a task at a fixed workload that can be expected of a system whose resources are improved

The following formula outlines the formula (Execution Time=ET)

$$ET_{new}=ET_{not\;affected}+\frac{ET_{affected}}{amount\;improved}$$

Equations for CPU Performance

$$CPU\;time=(\#\;of\;CPU\;clock\;cycles)\cdot(clock\;cycle\;time)$$

Note, $clock\;cycle\;time$ is shown below between $a$ and $b$.

Cycles per instruction (CPI) is shown in the following equation.

$$CPI=\frac{total\;\#\;of\;clock\;cycles}{instruction\;count}$$

Conversly, IPC (instructions per cycle) is shown in the following equation.

$$IPC=\frac{instruction\;count}{total\;\#\;of\;clock\;cycles}$$

In the equation below, please not $IC$ stands for Instruction Count

$$CPU\;time=IC\cdot CPI\cdot clock\;cycle\;time$$