Advanced Computer Architecture
Chapter 6: Prediction

Motivation

Prediction - a cross-cutting issue

Overview

The n-bit branch history table (BHT)- revisited

n-bit BHT - how well does it work?

N-bit BHT - why does it work so well?

Bias

Is local history all there is to it?

Global history

Two-level correlating branch predictor

Two-level correlating branch predictor

How many bits of branch history should be used?

Variations

Horses for courses

Extreme example - “go”

Some dynamic applications have highly-correlated branches

Combining predictors

Warm-up effects and context-switching

Warm-up...

Correlating branch prediction - Summary

Acknowledgements; finding out more

Prediction pay-off

When to gamble - predication

Instructions for predication

Instructions for predication

Predication versus prediction

Predication
- issues

Predicting multiple branches

More applns of prediction - data prefetching

More applns of prediction - cache bypass

More applns of prediction - value prediction

More applns of prediction - value prediction ...

Prediction - summary