Question

Postponing the introduction of signals with high switching rates (probability of switching close to 50%) can reduce the switching power consumption.

True or False

(Please explain).

Thank you

Answer 1

True

Explanation:

This is a part of Input Reordering to optimise power consumption.

The probabilities of A, B and C being 1 is listed in the figure. Since both circuits implement identical logic functionality, it is obvious that the activity at the output node Z is equal in both cases. The difference is the activity at the intermediate node. In the first circuit, this activity equals (1 - 0.5 * 0.2) (0.5 * 0.2) = 0.09. In the second case, the probability that a 0 -> 1 transition occurs equals (1 – 0.2 * 0.1) (0.2 * 0.1) = 0.0196. This is substantially lower. From this we learn that it is beneficial to postpone the introduction of signals with a high transition rate (i.e., signals with a signal probability close to 0.5). A simple reordering of the input signals is often sufficient to accomplish that goal.

PA-1) 0.5 Pe-1) 0.2 P(c-)-0.1