Intel 80286 User Manual

TABLE OF CONTENTS
Page
Reserved and Dedicated Interrupt Vectors ............................................................... 5-5
System Initialization ........................................................................................................ 5-7
CHAPTER 6
MEMORY MANAGEMENT AND VIRTUAL ADDRESSING
Memory Management Overview .................................................................................... 6-1
Virtual Addresses ............. ......... ...... ..... ....... ....... .................. ........... ............ ....... ............ 6-2
Descriptor Tables .................................................................................................. ......... 6-4
Virtual-to-Physical Address Translation ... ....... .................. ........... ........... .......... ...... ...... 6-6
Segments and Segment Descriptors ............................................................................. 6-7
Memory Management Registers ......... ..... ........ .......... ........ ...... ............... ...................... 6-9
Segment Address Translation Registers ................................................................... 6-9
System Address Registers ............ ....... ....... ...... .... ......... ..... ............ ................ ..... ...... 6-12
CHAPTER 7
PROTECTION
Introduction ..................................................................................................................... 7-1
Types of Protection .................................................................................................... 7-1
Protection Implementation ......................................................................................... 7-2
Memory Management and Protection ........................................................................... 7-4
Separation of Address Spaces .................................................................................. 7-5
LDT and GDT Access Checks ................................................................................... 7-5
Type Validation ........................................................................................................... 7-6
Privilege Levels and Protection ........................................................................ ............. 7-8
Example of Using Four Privilege Levels .................................................................... 7-8
Privilege Usage ........................................................................................................... 7-9
Segment Descriptor ....................................................................................................... 7-10
Data Accesses ............................................................................................................ 7-12
Code Segment Access ............................................................................................... 7-13
Data Access Restriction by Privilege Level ............................................................... 7-13
POinter Privilege Stamping via ARPL ......................................................................... 7-14
Control Transfers .................................................... ....................................................... 7-15
Gates ........................................................................................................................... 7-16
Call Gates ................................................................................................................ 7-17
Intra-Level Transfers via Call Gate ......................................................................... 7-18
Inter-Level Control Transfer
via Call Gates ............................................................ 7-19
Stack Changes Caused by Call Gates .............................................. ..................... 7-20
Inter-Level Returns ..................................................................................................... 7-20
CHAPTERS
TASKS
AND STATE TRANSITIONS
Introduction .....................................................................................................................
8-1
Task State Segments and Descriptors .......................................................................... 8-1
Task State Segment Descriptors ............................................................................... 8-3
Task Switching ............................................................................................................... 8·4
Task Linking ...................................................................................................................
8-7
Task Gates ..................................................................................................................... 8-8
CHAPTER 9
INTERRUPTS AND EXCEPTIONS
Interrupt Descriptor Table ..............................................................................................
9-1
Hardware Initiated Interrupts ......................................................................................... 9-2
vii
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Intel 80286 Specifications

General

Processor Type	Microprocessor
Clock Speed	6 MHz to 25 MHz
Transistor Count	134, 000
Addressable Memory	16 MB
Instruction Set	x86
Architecture	x86
Data Bus Width	16-bit
Address Bus Width	24-bit
Operating Modes	Real mode, Protected mode
Process Technology	1.5 µm
Voltage	5V
Introduced	1982
Package	68-pin PGA