Power

Dynamic Power

• The power a processor uses when in use
• $DP\propto V^2$
  • Increase clock rate → Increase voltage → Increase dynamic power
  • $V\propto \text{Clock Rate}$
• $\text{DP}\propto \frac{1}{2}\times \text{Capacitive load}\times {\text{Voltage}}^2\times \text{Frequency switched}$
  • Getting double the Performance in a processor requires four times the power
  • Multicore Parallelism is useful because it brings performance to a linear relationship with power

Static Power

• The power user when doing nothing
• $SP\propto V$
• Static power adds up over time so it does have an impact

Why Power Consumption Matters

• Power → Heat → Device damage
• Mobile devices have limited batteries

Relationship to Transistor Size

• Transistors are special Capacitors
  • The smaller the capacitor, the less voltage it needs
  • Allows it to charge and discharge faster, and use less power
• Smaller transistors need less power → generate less heat
• However, them being closer increases heat dissipation

$E=\int Pdt$