write write decode

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Assembly Language for Intel

Assembly Language for Intel - - Based Based Computers, 4

Computers, 4

^th^th

Edition Edition

Chapter 2: IA-32 Processor Architecture

Kip R. Irvine

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Chapter Overview Chapter Overview

• General Concepts

• IA-32 Processor Architecture

• IA-32 Memory Management

• Components of an IA-32 Microcomputer

• Input-Output System

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Irvine, Kip R. Assembly Language for Intel-Based Computers, 2003. 3

General Concepts General Concepts

• Basic microcomputer design

• Instruction execution cycle

• Reading from memory

• How programs run

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Basic Microcomputer Design [1/2]

• The central processor unit (CPU) is where all the calculations and logic operations take place.

• Clock synchronizes CPU operations

• Control unit (CU) coordinates sequence of execution steps

• Arithmetic logic unit (ALU) performs arithmetic and bitwise processing

Central Processor Unit (CPU)

Memory Storage Unit

registers

ALU clock

I/O Device

#1

I/O Device

#2 data bus

control bus address bus

CU

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Basic Microcomputer Design [2/2]

• The memory storage unit is where instructions and data are held while a computer program is running.

• A bus is a group of parallel wires that transfer data from one part of the computer to another.

• Data bus, address bus and control bus

Central Processor Unit (CPU)

Memory Storage Unit

registers

ALU clock

I/O Device

#1

I/O Device

#2 data bus

control bus address bus

CU

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Clock Clock

• Synchronizes all CPU and BUS operations

• Machine (clock) cycle measures time of a single operation

• A machine instruction requires at least one clock cycle to execute.

• A few instructions (e.g., the multiply instruction) requre in excess of 50 clocks.

• The duration of a clock cycle is the reciprocal of the clock’s speed

• Clock is used to trigger events

one cycle 1

0

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Instruction Execution Cycle Instruction Execution Cycle

• Fetch

• Decode

• Fetch operands

• Execute

• Store output

I-1 I-2 I-3 I-4

PC program

I-1 instruction register op1

op2

memory fetch

ALU registers

write decode

execute read

write

(output)

registers

flags

• The execution of a single machine instruction can be divided into a sequence of individual operations.

• Three primary operations: fetch, decode and execute.

• Two more steps are required when the instruction uses a memory operand: fetch operand and store output operand.

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Multi

Multi - - Stage Pipeline Stage Pipeline

• Pipelining makes it possible for a processor to execute instructions in parallel

• Instruction execution divided into discrete stages

S1 S2 S3 S4 S5

1

Cycles

Stages

S6

2 3 4 5 6 7 8 9 10 11 12

I-1

I-2

I-1

I-2

I-1

I-2

I-1

I-2

I-1

I-2

I-1

I-2

Example of a non- pipelined processor.

Many wasted cycles.

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Pipelined Execution Pipelined Execution

• More efficient use of cycles, greater throughput of instructions:

S1 S2 S3 S4 S5

1

Cycles

Stages

S6

2 3 4 5 6 7

I-1

I-2 I-1

I-2 I-1 I-2

For k states and n instructions, the number of required cycles is:

k + (n – 1)

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Wasted Cycles (pipelined) Wasted Cycles (pipelined)

• When one of the stages requires two or more clock cycles, clock cycles are again wasted.

S1 S2 S3 S4 S5

1

Cycles

Stages

S6

2 3 4 5 6 7

I-1 I-2 I-3

I-1

I-2 I-1

I-1 8

9

I-3 I-2

I-2 exe

10 11

I-3

I-3 I-1

I-2

I-3

k + (2n – 1)

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Superscalar Superscalar

A superscalar processor has multiple execution pipelines. In the following, note that Stage S4 has left and right pipelines (u and v).

S1 S2 S3 u S5

1

Cycles

Stages

S6

2 3 4 5 6 7

I-1 I-2 I-3 I-4

I-1

I-3 I-1

I-2 I-1 v

I-2

I-4 S4

8 9

I-3 I-4

I-2 I-3

10 I-4

I-2

I-4 I-1

I-3

k + n

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Reading from Memory Reading from Memory

• Multiple machine cycles are required when reading from memory, because it responds much more slowly than the CPU. The steps are:

• address placed on address bus

• Read Line (RD) set low to notify memory that a value is to be read

• CPU waits one cycle for memory to respond. During this cycle, the memory controller places the operand on the data bus (DATA)

• Read Line (RD) goes to 1, indicating that the data is on the data bus

Cycle 1 Cycle 2 Cycle 3 Cycle 4

Data Address

CLK

ADDR

RD

DATA

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Cache Memory Cache Memory

• High-speed expensive static RAM both inside and outside the CPU.

• Level-1 cache: inside the CPU

• Level-2 cache: outside the CPU

• Cache hit: when data to be read is already in cache memory

• Cache miss: when data to be read is not in cache

memory.

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How a Program Runs [1/2]

Operating system

User

Current directory

System path

Directory entry

sends program name to

gets starting cluster from

searches for program in

loads and starts

Program returns to

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How a Program Runs [2/2]

• The user issues a command to run a certain program.

• The OS searches for the program’s filename (in the current directory or predetermined list of directories)

• The OS retrieves basic information about the program’s file from the disk directory.

• The OS loads the program file into memory.

• The CPU begins to execute the program (process).

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Multitasking Multitasking

• OS can run multiple tasks at the same time.

• Scheduler utility assigns a given amount of CPU time to each running program.

• Rapid switching of tasks

• Gives illusion that all programs are running at once

• Round-robin scheduling

• The processor must support task switching.

• The processor saves the state (e.g., registers, variables, program counter) of each task before switching to a new one.

• OS can assign varying priorities to tasks.

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IA IA - - 32 Processor Architecture 32 Processor Architecture

• Modes of operation

• Basic execution environment

• Floating-point unit

• Intel Microprocessor history

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Modes of Operation Modes of Operation

• Protected mode

• Programs are given separate memory areas (called segments)

• Windows, Linux

• Real-address mode

• Implements the programming environment of the Intel 8086 processor

• Native MS-DOS

• All Intel processors boot in Real-address mode

• System management mode

• Provides an operating system with a mechanism for implementing

• Power management, system security, diagnostics

• Implemented by computer manufactures

• Virtual-8086 mode

• hybrid of Protected and Real-address modes

• While in Protected mode, the processor can directly execute Real-address mode program in a safe multitasking environment.

• each program has its own 8086 computer

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Basic Execution Environment Basic Execution Environment

• Addressable memory

• General-purpose registers

• Index and base registers

• Specialized register uses

• Status flags

• Floating-point, MMX, XMM registers

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Addressable Memory Addressable Memory

• Protected mode

• 4 GB

• 32-bit address

• Real-address and Virtual-8086 modes

• 1 MB space

• 20-bit address

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Registers Registers

CS SS DS

ES

EIP EFLAGS

16-bit Segment Registers EAX

EBX ECX EDX

32-bit General-Purpose Registers

FS GS EBP

ESP ESI EDI

• Registers are high-speed storage locations directly inside the CPU

• Optimized for speed (e.g., loop processing)

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Accessing Parts of Registers Accessing Parts of Registers

• Used for arithmetic and data movement

• Use 8-bit name, 16-bit name, or 32-bit name

• Applies to EAX, EBX, ECX, and EDX

AH AL

16 bits 8

AX

EAX

8

32 bits 8 bits + 8 bits

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Index and Base Registers Index and Base Registers

• Some registers have only a 16-bit name for their

lower half:

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Some Specialized Register Uses [1/2]

• General-Purpose

• EAX – accumulator (used by multiplication and division instructions)

• ECX – loop counter

• ESP – stack pointer addresses data on the stack

• ESI, EDI – source/destination index registers (for high- speed memory transfer)

• EBP – extended frame pointer (used by high-level

languages to reference function parameters and local

variables)

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Some Specialized Register [2/2]

• Segment (as base locations for pre-assigned memory areas)

• CS – code segment

• DS – data segment

• SS – stack segment

• ES, FS, GS - additional segments

• EIP – instruction pointer

• Containing the address of the next instruction to be executed

• EFLAGS

• Status and control flags

• Control the operation of the CPU or reflect the outcome of some CPU operation

• each flag is a single binary bit

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Flags Flags

• Control Flags

• Direction

• Interrupt

• Status Flags

• Carry

• unsigned arithmetic out of range

• Overflow

• signed arithmetic out of range

• Sign

• result is negative

• Zero

• result is zero

• Auxiliary Carry

• carry from bit 3 to bit 4 in an 8-bit operand

• Parity

• sum of “1” bits is an even number

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Floating

Floating - - Point, MMX, XMM Registers Point, MMX, XMM Registers

• Eight 80-bit floating-point data registers

• ST(0), ST(1), . . . , ST(7)

• used for high-speed floating-point arithmetic

• Eight 64-bit MMX registers

• Eight 128-bit XMM registers for single-instruction multiple-data (SIMD) operations

ST(0) ST(1) ST(2) ST(3) ST(4) ST(5) ST(6) ST(7)

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Intel Microprocessor History Intel Microprocessor History

• Intel 8086

• Intel 80286

• IA-32 processor family

• P6 processor family

• CISC and RISC

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Early Intel Microprocessors Early Intel Microprocessors

• Intel 8086/8088

• Mark the beginning of the modern Intel Architecture family

• IBM-PC used 8088

• 1 MB addressable RAM

• 16-bit registers

• 16-bit data bus (8-bit for 8088 – low-cost microcontroller)

• separate floating-point unit (8087)

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The IBM

The IBM - - PC/AT Computer PC/AT Computer

• Intel 80286

• 16 MB addressable RAM

• Protected memory

• several times faster than 8086

• 80287 floating point unit

• Downward Compatibility

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Intel IA

Intel IA - - 32 Family 32 Family

• Intel386

• 4 GB addressable RAM, 32-bit registers, paging (virtual memory)

• Intel486

• instruction pipelining

• Pentium

• superscalar, 32-bit address bus, 64-bit

internal data path

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Intel P6 Family Intel P6 Family

• Based on a new micro-architecture design that

improves execution speed (extension of the basic IA- 32 architecture)

• Pentium Pro

• Advanced optimization techniques in microcode

• Pentium II

• MMX (multimedia) instruction set

• Pentium III

• SIMD (streaming extensions) instructions with special 128-bit registers designed to move large amounts of data quickly

• Pentium 4

• NetBurst micro-architecture, tuned for multimedia

applications

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CISC and RISC CISC and RISC

• CISC – complex instruction set

• large instruction set

• high-level operations

• High-level language compilers would have less work

• requires microcode interpreter

• Complex instructions require a long time for the processor to decode and execute

• examples: Intel 80x86 family

• RISC – reduced instruction set

• simple, atomic instructions (for pipelining)

• small instruction set

• directly executed by hardware

• High-speed engineering and graphics workstation use RISC processors

• examples:

• ARM (Advanced RISC Machines)

• DEC Alpha (now Compaq)

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IA IA - - 32 Memory Management 32 Memory Management

• Real-address mode

• Calculating linear addresses

• Protected mode

• Multi-segment model

• Paging

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Real Real - - Address mode Address mode

• 1 MB RAM maximum addressable (00000~FFFFFh)

• Application programs can access any area of memory

• Single tasking

• Supported by MS-DOS operating system

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Segmented Memory Segmented Memory

• The original 8086 processor had only 16-bit registers, which can not directly represent a 20-bit address

• Segmented memory addressing: absolute (linear) address is a combination of a 16-bit segment value added to a 16-bit offset

10000 20000 30000 40000 50000 60000 70000 80000 90000 A0000 B0000 C0000 D0000 E0000 F0000

8000:0000 8000:FFFF

seg ofs

8000:0250 0250

linear addresses

one segment

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Calculating Linear Addresses Calculating Linear Addresses

• Given a segment address, multiply it by 16 (add a hexadecimal zero), and add it to the offset

• Example: convert 08F1:0100 to a linear address

Adjusted Segment value: 0 8 F 1 0 Add the offset: 0 1 0 0 Linear address: 0 9 0 1 0

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Your turn . . . Your turn . . .

What linear address corresponds to the segment/offset address 028F:0030?

028F0 + 0030 = 02920

Always use hexadecimal notation for addresses.

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Your turn . . . Your turn . . .

What segment addresses correspond to the linear address 28F30h?

Many different segment-offset addresses can produce the linear address 28F30h. For example:

28F0:0030, 28F3:0000, 28B0:0430, . . .

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Protected Mode Protected Mode

• 4 GB addressable RAM

• (00000000 to FFFFFFFFh)

• Each program assigned a memory partition which is protected from other programs

• Designed for multitasking

• Supported by Linux & MS-Windows

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Flat Segmentation Model Flat Segmentation Model

• All segments are mapped to the entire 32-bit physical address space of the computer.

• At least two segments: one for program code and one for data

• Each segment is defined by a segment descriptor, a 64-bit value stored in a table known as the global descriptor table (GDT)

00000000 0040 ----

base address limit access

Segment descriptor in the Global Descriptor Table

not usedPhysical RAM

FFFFFFFF (4GB)

00040000

00000000

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Multi

Multi - - Segment Model Segment Model

• Each program has a local descriptor table (LDT)

• holds descriptor for each segment used by the program

3000 RAM

00003000

Local Descriptor Table

0002 00008000 000A 00026000 0010

base limit access

8000 26000

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Paging Paging

• Supported directly by the CPU

• Divides each segment into 4096-byte blocks called pages

• Sum of all programs can be larger than physical memory

• Part of running program is in memory, part is on disk

• Virtual memory manager (VMM) – OS utility that manages the loading and unloading of pages

• Page fault – issued by CPU when a page must be

loaded from disk

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Components of an IA

Components of an IA - - 32 Microcomputer 32 Microcomputer

• Motherboard

• Video output

• Memory

• Input-output ports

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Motherboard Motherboard

• The heart of a microcomputer CPU socket

• External cache memory slots

• Main memory slots

• BIOS (a collection of functions that communicate directly with hardware devices) chips

• Sound synthesizer chip (optional)

• Video controller chip (optional)

• IDE (hard and CD-ROM drives), parallel, serial, USB

• PCI bus connectors (expansion cards)

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Intel D850MD Motherboard Intel D850MD Motherboard

dynamic RAM Intel 486 socket

Speaker

mouse, keyboard,

parallel, serial, and USB connectors

Battery Video chip

Power connector

memory controller hub

Diskette connector PCI slots

I/O Controller Firmware hub

Audio chip

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Video Output Video Output

• Video controller

• on motherboard, or on expansion card

• A special-purpose microcomputer, relieving the

primary CPU of the job of controlling video hardware

• Video memory (VRAM)

• Video CRT Display

• uses raster scanning

• horizontal retrace

• vertical retrace

• Direct digital LCD monitors

• no raster scanning required

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Memory Memory

• ROM

• read-only memory (permanently burned into a chip)

• EPROM

• erasable programmable read-only memory (be erased slowly with ultraviolet light)

• Dynamic RAM (DRAM)

• inexpensive; must be refreshed constantly

• Static RAM (SRAM)

• expensive; used for cache memory; no refresh required

• Video RAM (VRAM)

• dual ported (refreshing+writing); optimized for constant video refresh

• Allocated on a video controller

• CMOS RAM

• system setup information

• On the system motherboard

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Input

Input - - Output Ports [1/2] Output Ports [1/2]

• USB (universal serial bus)

• intelligent high-speed connection to devices

• up to 12 megabits/second

• USB hub connects multiple devices

• enumeration: computer queries devices

• Parallel

• short cable (less than 10 feet), high speed

• common for printers

• bidirectional, parallel data transfer (8 or 16

bits simultaneously)

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Input

Input - - Output Ports [2/2] Output Ports [2/2]

• Serial

• RS-232 serial port

• one bit at a time

• uses long cables and modems

• 16550 UART (Universal Asynchronous Receiver Transmitter) controls the serial ports.

• Located either on the motherboard or on an adapter card

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Levels of Input

Levels of Input - - Output Output

• Level 3: Call a library function (C++, Java)

• easy to do; abstracted from hardware; details hidden

• slowest performance

• Level 2: Call an operating system function

• specific to one OS; device-independent

• E.g., writing entire strings to files, reading string from the

keyboard, allocating blocks of memory for application programs

• medium performance

• Level 1: Call a BIOS (basic input-output system) function

• may produce different results on different systems

• knowledge of hardware required

• usually good performance

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Displaying a String of Characters Displaying a String of Characters

When a HLL program displays a string of characters, the following steps take place:

1. Application program writes the string to standard output.

2. The library function calls OS, passing a string pointer.

3. OS passes the ASCII code and color of each character to BIOS. OS also calls BIOS function to control the cursor.

4. BIOS maps each character to a particular system font and sends it to a hardware port attached to the video controller card.

5. The video controller card generates hardware signals to the video display.

Application Program

OS Function

BIOS Function

Hardware Level 0

Level 1 Level 2 Level 3

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ASM Programming levels ASM Programming levels

ASM Program

OS Function

BIOS Function

Hardware Level 0

Level 1 Level 2

ASM programs can perform input-output at

each of the following levels:

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