The Unabridged Pentium 4 IA32 Processor Genealogy

Enhanced Branch Prediction

Enhanced Static Branch Predictor

The Static Branch Predictor (see “The Static Branch Predictor” on page 911) is consulted when a miss occurs on the Front-End BTB (i.e., the BTB doesn't have any execution history on a conditional branch instruction). In the earlier versions of the processor, it would predict a backward relative conditional branch as taken and a forward branch as not taken. This approach works well for a backward branch at the end of a loop, but not all backward-relative branches reside at the bottom of a loop.

The 90nm processor's Static Branch Predictor uses the distance that the branch jumps backward as well as the condition on which the branch depends to try and determine if the branch resides at ...