1.7 The Power Wall

• I really don't know this. These are notes on the section.
• But this is important.
• Goodbye Moore's law
• See figure 1.16, page 40
• $\text{Energy} \propto \frac{1}{2} \text{Capacitive Load} \times \text{Voltage}^2 \times \text{Frequency Switched}$
  • This is per transistor
  • The capacitive load is based on how many other transistors this one is hooked to (fannout)
  • We continue to add more transistors
  • We want to drive them faster
• We have managed to reduce the voltage quite a bit
  • However, reducing the voltage makes the transistors more leaky.
  • This means that the current is bypassing the transistor and it is not working.
  • They claim that 40% of the power in modern chips is lost to leaking.
  • If we go any lower, we will not get computation, just an expensive heater.
• So we can't run them faster, we have hit the power wall.

1.8 The Switch to Multiprocessors

• We still are getting more transistors on a chip, so what do we do?
• Build more cores.
• But parallel programming is hard.
• So too bad for us.