Chapter 4 Introduction

Morgan Kaufmann Publishers 31 January 2013Speculationn Predict branch and continue issuingn Don’t commituntil branch outcome determinedn Load speculationn Avoid load and cache miss delayn Predict the effective addressn Predict loaded valuen Load before completing outstanding storesn Bypass stored values to load unitn Don’t commit load until speculation clearedCSE 420 Chapter 4 — The Processor — 123Why Do Dynamic Scheduling?n Why not let the compiler schedule code?n Not all stalls are predicablen e.g., cache missesn Can’t always schedule around branchesn Branch outcome is dynamically determinedn Different implementations of an ISAhave different latencies and hazardsCSE 420 Chapter 4 — The Processor — 124