System Architecture | Intel 80386 specification

SYSTEM ARCHITECTURE

Memory-mapped devices can be protected by the standard 80386 segment and page protection mechanisms.

In addition to its memory address space, the 80386 has a 64 kilobyte I/O address space. Devices mapped into this space are manipulated with the Input, Output, Input String, and Output String instructions. The first two instructions transfer a byte, word, or dword to or from the EAX register. The latter two instructions transfer a string of bytes, words, or dwords to or from memory.

The 80386 I/O instructions are privilege level sensitive. In the Flags register is a field called I/O Privilege Level (lOPL), which defines the minimum privilege level at which the running task can execute I/O instructions. (IOPL is loaded from the TSS so tasks can have different IOPLs). For example, if a task's 10PL is I, then the task cannot issue I/O instructions except

when it is running at privilege level I or O. The . 10PL mechanism supports multilevel protected operating systems in which, for example, critical and stable kernel procedures run at privilege level 0, and more volatile I/O procedures run at privilege level I; in this case the operating system has only to set IOPL to I when it creates a task. Because IOPL is task-specific, trusted tasks can be allowed execute I/O instructions while running application code, allowing them, for example, to directly manipulate special devices, for which no operating system driver is available.

To perform direct memory access (DMA) I/O, an 80386 operating system passes a physical address to the DMA controller and must guar- antee that the target segment(s) and/ or page(s) do not move during the transfer. One way to mark pages "locked for I/O" is to use one of the three user-defined page table bits.

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Intel 80386 manual System Architecture

Contents

Page Inter Intel Corporation Table of Contents Chapter Architectural Compatibility Chapter Highlights Page 32-bit Architecture High-performance Implementation Highlights Configurable Protection Virtual Memory SupportExtended Debugging Support Object Code Compatibility Summary Application Architecture Page Registers General RegistersFlags and Instruction Pointer Numeric Coprocessor Registers Memory and logical Addressing Segment and Descriptor Registers Logical Address Translation Addressing Modes Data Types and Instructions Principal Data Types Numeric Coprocessor Data Types Other InstructionsStack Instructions ~.,...I-------.-1 Byte String LII Miscellaneous Instructions Chapter System Architecture Page System Registers Multitasking Task Switching Task State Segment Addressing Address Translation Overview Segments Address Translation Overview Principal Descriptor Fields ~~~~~.II~~~ Pages Virtual Memory Linear to Physical Address Translation I I I Protection Privilege USing Privilege Levels Privileged Instructions Segment Protection Protection Interrupts and Exceptions 10. Gates as Protected Entry Points Interrupt Descriptor Table Debug Eceptions and Registers System Architecture Page Architectural Compatibility Page 80286 Compatibility Real and Virtual 86 Modes Architectural Compatibility Trapping Virtual 861\11ode System Calls Page Chapter Hardware Implementation Page Chapter Hardware Implementation Hardware Implementation Clock Data and Address Buses Bus Cycle Definition Bus Cycle Control Non-pipelined Bus Cycle Timing Bus Cycles with Pipelined Addresses Dynamic Bus Sizing Processor Status and ControlCoprocessor Control Mixed 16- and 32-bit Accesses Chapter Data Sheet Page 80386 Update Notice Table of Contents Segment Descriptor Cache Descriptor Tables IntroductionInterrupt Descriptor Table Privilege Validation Functional Data Initiating and Maintaining Pipelined Address Package Thermal Specification3.4 Pipelined Address with Dynamic Data Bus Sizing Base Architecture Introduction Register Overview Instruction Pointer Register DescriptionsGeneral Purpose Registers Flags Register TSS Segment Registers Segment Registers Descriptor Registers Loaded AutomaticallyOther Segment Physical Base Address Segment Limit Flects the current state of the ET bit Segment Descriptor RegistersControl Registers MSW System Address Registers TS Task Switched, bitFault Linear Address Register CR2 Directory Base Register CR3 Register Accessibility Debug and Test RegistersCompatibility Gdtr Instruction Set OverviewIopl Idtr 2a Data Transfer 2 80386 Instructions2dLogical Instructions 2b Arithmetic Instructions 2g High Level Language Instructions 2e Bit Manipulation Instructions2f. Program Control Instructions 2h Protection Model Addressing Modes Overview Register and Immediate Modes3 32-Bit Memory Addressing Modes Addressing Mode Calculations Differences Between 16 and 32 Bit Addresses Base Register BX,BP Index Register SI,DI Scale Factor DisplacementData Types None LilliililillIl Sign ED rrrrrrrrl Memory Organization IntroductionAddress Spaces I/O Space Segment Register Usage Interrupt Processing InterruptsInterrupts and Ecep~ions Maskable Interrupt Non-Maskable Interrupt Software Interrupts Interrupt and Exception Priorities NMI 2.INTR Reset and Initialization Double FaultInstruction Restart Self-Test TLB TestingTestability Debugging Support Breakpoint Instruction Single-Step TrapDebug Registers DR3 DR1DR2 DR4 Encoding Causing Breakpoint Usage Real Mode Architecture Real Mode Introduction Debug Status Register DR6 Xchg SET/RESET/COMPLEMENTMemory Addressing ADD, OR, ADC, SBB Reserved Locations IntierruptsShutdown and Halt Protected Mode Addressing Addressing Mechanism Descriptor Tables Segmentation IntroductionTerminology Descriptor Tables Introduction Address DescriptorsByte Segment Base 15 Segment Limit 15 Dptm typ , data gm,nt System Descriptor Formats Word SelectorOffset 15 Offset 31 Selector Fields Differences Between 386 and 286 DescriptorsSegment Base 15 Segment Descriptor Cache Nil R~L ~~~~~~~EL~~E~ ~A~~ ~I~I! ttl ~!~~~~E L~~E~~~s~ I~I! ~ J ~~?~~~~EL~~E~B~~E ~I~I~ tJ1 Protection Concepts Rules of PrivilegePrivilege Levels Privilege Level Transfers RET,IRET GOT/LOTCall CALL, JMP 80386 Task Switching Call Ga~es Initialization and Transition to Protected Mode Infef Systems Tools for Building ProtectedPaging Paging Concepts Descriptor Base Register Paging OrganizationMechanism Directory Tables Level Protection R/W, U/S BitsFrame Address 31 Reserved DIRECTORY/TABLE Entries Translation Lookaside Buffer Paging Operation Virtual 8086 Environment Paging In Virtual ModeAccess Type Executing 8086 Programs Protection and 1/0 Permission Bitmap 24. Virtual 8086 Environment Memory Management Interrupt Handling Entering and Leaving Virtual Task Switches TO/FROM Virtual 8086 Mode ·25.Virtual 8086 Environment Interrupt and Call Handling For state saving i.e. push all registers in prolog, pop Introduction Clock CLK2 Data Bus do through Address Bus BEO# through BE3#, A2 through A31 Bus Cycle Definition Signals W/R#, D/C#, MIIO#, LOCK# Bus Control Signals Introduction Bus Arbitration Signals Coprocessor Interface Signals Interrupt Signals Signal Summary Memory and 1/0 Spaces BEO# Memory and 110 Organization Dynamic Data Bus Sizing Interfacing with 32- and 16-Bit Memories Cycles 1 and 1a Operand Alignment BEO# BHE# BLE# AD Li,\~~ P1 1.p2 .p1 1.p2 .p1 1.p2 .p1 1.p2 .p1 1.p2 .p1 1.p2 .p1 Address Pipelining ·9.Fastest Read Cycles with Pipelined Address Timing Address signal A2 selects bank Bit datapath to each bank TWO-BANK Interleaved MemoryFOUR-BANK Interleaved Memory Read and Write Cycles Introduction Xxxi Xxxix NON-PIPELINED AddressXxxxx Ixxxx Ixxx 13 80386 Bus States not usIng pipelined address 3.3 NON·PIPELINED Address with Dynamic Data BUS Sizing ·14Asserting BS16# zero wait states, non·pipelinedaddress ~~~~ DOO¥ Xixxxxx ValidXixxxx ,XXXXY BSI6# XXX XXx XXX X .. IXXXXwOO~ J, XXX XXX1/ \ B516# ~~..tJ.~~~~~~~ BS16 # 44~~~...l-.lI...l Ready # 44~~.lI...l/l Bus Sizing with Pipelined Address ~ ,T1-T~-T2PJ ,T1PT2PJ Idle non-pipelined pipelined PipelinedAcknowledge IO#, D/c# Ffi 20 Complete Bus States including pipelined address Xxixxy ~ /..XIXXY Xxxxy ~j XDONTCAR~X~ x~ ~X~~lKX~ /..XXXXXxxxx IXXXXIXXXXI.. /..DXXXIXXX ~ Xxxxiy ~ -XXIXXY Interrupt Acknowledge Inta Cycles ~--cp--- ----- ----- ----- ----- ~ Halt Indication Cycle 23.Halt Indication Cycle Shutdown Indication Cycle 24. Shutdown Indication Cycle Other Functional Descriptions Reset During Hold AcknowledgeBus Activity During and Following Reset Entering and Exiting Hold Acknowledge 26. Requesting Hold from Active Bus NA # negated SELF-TEST Signature Component and Revision Identifiers Component Revision Component Revision Stepping Identifier Name Software Testing for Coprocessor Presence CMD1 Mechanical Data Introduction PIN Assignment 000 0 0 0 000 0 0 Vee Vss Package Dimensions and Mounting 1654189~1 Package Thermal Specification Measure PGA Case Temperature Infef80386 Ill Power and Grounding Electrical Data D.C. Specifications Maximum Ratings A.C. Specifications 1 A.C. Spec Definitions102 2 A.C. Specification Tables ·4 -16 A.C. Characteristics Symbol Parameter 80386-16Unit Min Max Operating Frequency MHz Half of CLK2 16 A.C. Characteristics Symbol Parameter Symbol Parameter Min80386-16 Min Unit Max 3 A.C. Test Loads 4 A.C. Timing Waveforms 80386 ~QW~OOg OOOIP@OOIMl~iiO@OO 106 MAX Itm PI~ Instruction SET 80386 Instruction Encoding 8o386Instructlon Set CIock Count Summary 111 ·1 Instruction Set Clock Count Summary 112 80386 Instructlon Set CIockCount S ummary Contlnued RIm ·1 80386 Instruction Set Clock Count Summary Doubleword Instruction Set Clock Count Summary 115 Instruction Set Clock Count Summarycontlnued BIT Manipulation Instruction Set Clock Count Summar +ml 7+ml 80386 Ins ruefIon SetCIoek CountSummary ConrInued Protected 119 120 80386 Instructlon Set CIockCountSummaay Contmued Interrupt Instructions O3861nstructlon Set CIockCount Summary Contlnued Bound Infef80386 80386 nstructlon Set CIockCount Summary Contlnued Ns ruetIon StCIe oekCount 5 ummary Contlnued Madear Overview ~~~\ Field 2 32-Bit Extensions of the Instruction SetEncoding of Instruction Fields Bits Encoding of Address Mode 11010 OsbxOSBX+d16 EOI OS EAX Scale Factor NB/AE Encoding of Operation DirectionNAE NE/NZ Domestic Sales Offices California United States