Itanium Rising: Breaking Through Moore's Second Law of Computing Power

Predication

Predication refers to the ability to better manage branches in a given program. Predication is a great example of the architecture's ability to do multiple things in parallel. A typical out-of-order execution engine maintains a couple of different program counters at the same time. One keeps track of the program instruction currently being executed, while the other is looking ahead at instructions that will be executed in the future. It builds a pipeline, or queue, to speed the transaction when it actually occurs. An excellent example of how this works is shown in Figure 8-1.

Figure 8-1. Predication Process Illustrated

This whole process ...