# Homework Help: Computer architecture power savings question

1. Feb 3, 2012

### SpiffyEh

1. The problem statement, all variables and given/known data
Server farms such as Google and Yahoo! provide enough compute capacity for the highest request rate of the day. Imagine that most of the time these servers operate at only 60% capacity. Assume further that the power does not scale linearly with the load; that is, when the servers are operating at 60% capacity, they consume 90% max power. The servers could be turned off, but they would take too long to restart in response to more load. A new system has been proposed that allows for a quick restart but requires 20% of the max power while in this "barely alive" state.
a) How much power savings would be achieced by turning off 60% of the servers?
b) How much power savings would be achieved by placing 60% of the servers in the "barely alive" state?
c) How much power would be saved by reducing the voltage by 20% and frequency by 40%?
d) How much power savings would be achieced by placing 30% of the servers in the "barely alive" state and 30% off?

2. Relevant equations
Power dynamic = 1/2 * capacitive load * voltage^2 * frequency switched

3. The attempt at a solution
For part a) the servers that are on are running at 100% their power so i'm guessing 60% of the power would be saved?

I don't understand how to go about trying to solve the rest of them