Chapter 7

CPUs: Microcode, Protection, And Processor Modes


7.1 Introduction
95
7.2 A Central Processor
95
7.3 CPU Complexity
96
7.4 Modes Of Execution
97
7.5 Backward Compatability
97
7.6 Changing Modes
98
7.7
Privilege And Protection
97
7.8
Multiple Levels Of Protection
98
7.9
Microcoded Instructions
99
7.10
Microcode Variations
100
7.11
The Advantage of Microcode
102
7.12
Making Microcode Visible To Programmers
103
7.13
Vertical Microcode
103
7.14
Horizontal Microcode
104
7.15
Example Horizontal Microcode
105
7.16
A Horizontal Microcode Example
107
7.17
Operations That Require Multiple Cycles
108
7.18
Horizontal Microcode And Parallel Execution
109
7.19
Look-Ahead And High Performance Execution
110
7.20
Paralallelism And Execution Order
111
7.21
Out-Of-Order Instruction Execution
111
7.22
Conditional Branches And Branch Prediction
112
7.23
Consequences For Programmers
113
7.24
Summary
113