Chapter 4 Introduction

Morgan Kaufmann Publishers 31 January 2013Calculating the Branch Targetn Even with predictor,still need to calculate the target addressn 1-cycle penalty for a taken branchn Branch target buffern Cache of target addressesn Indexed by PC when instruction fetchedn If hit and instruction is branch predicted taken,can fetch target immediatelyCSE 420 Chapter 4 — The Processor — 93Exceptions and Interruptsn “Unexpected” eventsrequiring change in flow of controln Different ISAs use the terms differentlyn ExceptionnArises within the CPUn e.g., undefined opcode, overflow, syscall, …n Interruptn From an external I/O controllern Dealing with them without sacrificing performanceis hard§4.9 ExceptionsCSE 420 Chapter 4 — The Processor — 94