ECE291 Lecture 1 All about computers. ECE 291 Lecture 1Page 2 of 41 Lecture outline Top-down view of computers Processor architecture RegistersMemoryPeripherals

ECE291ECE291

Lecture 1Lecture 1

All about computersAll about computers

ECE 291 Lecture 1ECE 291 Lecture 1

Page Page 22 of 41 of 41

Lecture outlineLecture outline

Top-down view of computersTop-down view of computers

Processor architectureProcessor architecture

RegistersRegisters

MemoryMemory

PeripheralsPeripherals

Assembly primerAssembly primer

AssignmentsAssignments



Computers from 50,000 feetComputers from 50,000 feet

Basic componentsBasic components MouseMouse KeyboardKeyboard MonitorMonitor PrinterPrinter ScannerScanner JoystickJoystick ““The box”The box”



Computers from 10,000 feetComputers from 10,000 feet

Sound cardSerialSCSI

Parallel

Keyboard/Mouse USB ExpansionVGA

Network

Power



Computers from 100 feetComputers from 100 feet

Cooling fan

Pow

er s

uppl

y

Mem

ory P

rocessor

Expansion bus

Motherboard

IDE and SCSI cables and devices



Motherboard


CPU

Memory

ExpansionBus

Peripherals

Control

Data

Address



Motherboard


Processor

8088

8086

80286

80386dx

80486

80586/Pentium (Pro)

Data Bus

8

16

16

32

32

64

Address Bus

20

20

24

32

32

32

Max Addressable Memory

1,048,576 (1Mb)

1,048,576 (1Mb)

16,777,21 (16Mb)

4,294,976,296 (4Gb)

4,294,976,296 (4Gb)

4,294,976,296 (4Gb)



Computers from 1 micronComputers from 1 micronCentral Processing Unit – The Processor

ALUBIU

Control

Controlregisters

Generalpurposeregisters

Special(floating-point,

flag, sse)

Control

Data

Address



The processorThe processor

It’s a state machineIt’s a state machine

Has a set of hard-coded operationsHas a set of hard-coded operations Each operation has an associated code;Each operation has an associated code;

an “opcode”an “opcode” Some examples are MOV, ADD, SUB, ANDSome examples are MOV, ADD, SUB, AND

All it can do is move data or perform some All it can do is move data or perform some calculation on datacalculation on data

Very simple, right?Very simple, right?



The processor - componentsThe processor - components

CPU RegistersCPU Registers Special memory locations constructed from flip-flops and Special memory locations constructed from flip-flops and

implemented on-chipimplemented on-chip E.g., accumulator, count register, flag registerE.g., accumulator, count register, flag register

Arithmetic and logic Unit (ALU)Arithmetic and logic Unit (ALU) Where most of the action takes place inside the CPUWhere most of the action takes place inside the CPU

Bus Interface Unit (BIU)Bus Interface Unit (BIU) Responsible for controlling the address and data busses when Responsible for controlling the address and data busses when

accessing main memory and data in the cacheaccessing main memory and data in the cache

Control Unit and Instruction SetControl Unit and Instruction Set CPU has a fixed set of instructionsCPU has a fixed set of instructions E.g. MOV, CMP, ADD, JMPE.g. MOV, CMP, ADD, JMP



The registersThe registers

Small memory locations that are quickly Small memory locations that are quickly accessible by the processoraccessible by the processor

Hold data and results for operationsHold data and results for operations

Point to memory locationsPoint to memory locations

Contain status information about the Contain status information about the results of operationsresults of operations



80x86 registers80x86 registers

Accumulator

EAX

AH AL

AX

Base

EBX

BH BL

BX

Count

ECX

CH CL

CX

Data

EDX

DH DL

DX

General Purpose

Instr Pointer

EIP

IP

Flags

EFLAG

FLAG

Special Registers

Stack Segment

Code SegmentCS

Data SegmentDS

Extra SegmentES

SS

FS

GS

Segment Registers

Stack Pointer

ESP

SP

Base Pointer

EBP

BP

Dest Index

EDI

DI

Source Index

ESI

SI

Index Registers



Register specificsRegister specifics

Accumulator (AL, AH, AX, EAX)Accumulator (AL, AH, AX, EAX) Usually stores results from the ALUUsually stores results from the ALU It “accumulates” totals from math operationsIt “accumulates” totals from math operations General purposeGeneral purpose

Base (BL, BH, BX, EBX)Base (BL, BH, BX, EBX) Usually holds addresses – points to memory Usually holds addresses – points to memory

locationslocations




Count (CL, CH, CX, ECX)Count (CL, CH, CX, ECX) Counting and loopingCounting and looping Certain instructions automatically decrement Certain instructions automatically decrement

the count registerthe count register

Data (DL, DH, DX, EDX)Data (DL, DH, DX, EDX) Usually contains data for instructionsUsually contains data for instructions Contain the most significant bytes of 16-bit Contain the most significant bytes of 16-bit

Mul/div’sMul/div’s




Stack pointer (SP, ESP)Stack pointer (SP, ESP) Used by stack operationsUsed by stack operations Usually you don’t want to mess with this oneUsually you don’t want to mess with this one

Base pointer (BP, EBP)Base pointer (BP, EBP) Addresses stack memoryAddresses stack memory Can be used to read subroutine argumentsCan be used to read subroutine arguments




Source index (SI, ESI)Source index (SI, ESI) Often used to address a source array or string Often used to address a source array or string

data typedata type

Destination index (DI, EDI)Destination index (DI, EDI) Often used to address a destination array or Often used to address a destination array or

string data typestring data type




Code segment (CS)Code segment (CS) Points to the area in memory where Points to the area in memory where

instructions are storedinstructions are stored

Instruction pointer (IP)Instruction pointer (IP) An index into the code segment that points to An index into the code segment that points to

the next instruction to be executedthe next instruction to be executed

Data segment (DS)Data segment (DS) Points to the area in memory where data Points to the area in memory where data

needed by a program is storedneeded by a program is stored




Stack segment (SS)Stack segment (SS) Points to the area in memory containing the Points to the area in memory containing the

system’s FIFO stack. We’ll have a whole system’s FIFO stack. We’ll have a whole lecture on this.lecture on this.

ES, FS, GSES, FS, GS Extra segment registers available to point to Extra segment registers available to point to

additional data segments should that be additional data segments should that be necessary.necessary.



MemoryMemory

System memory or RAM holds data and System memory or RAM holds data and instruction opcodes that are being used by instruction opcodes that are being used by the CPUthe CPU

Organized in banks, usually even and oddOrganized in banks, usually even and odd

Always byte addressableAlways byte addressable

More on all this tomorrowMore on all this tomorrow



Memory access exampleMemory access example

CPU wants to read memory at address 12345h

CPU MemoryRead Signal

Data

12345h



Memory organizationMemory organization

AB1 FF55 1214 3376 DE01 46F1 24E9 1190 87

3

5

7

9

B

D

F

0

2

4

6

8

A

C

E

Odd Bank Even Bank

Data Bus (15:8) Data Bus (7:0)




In Real Mode:In Real Mode: The address bus is 20-bits for memory The address bus is 20-bits for memory

operations.operations. 222020 = 1MB = how much memory an x86 = 1MB = how much memory an x86

processor can address in real modeprocessor can address in real mode The data bus is 16-bits which means it can The data bus is 16-bits which means it can

transfer two bytes in one operationtransfer two bytes in one operation Limited to 16-bit registersLimited to 16-bit registers




In Protected Mode:In Protected Mode: The memory address bus is 32-bitsThe memory address bus is 32-bits 223232 = 4GB = the maximum addressable = 4GB = the maximum addressable

amount of memory in modern x86 processorsamount of memory in modern x86 processors Data bus is also 32-bits meaning four bytes Data bus is also 32-bits meaning four bytes

can be transferred in a single operationcan be transferred in a single operation Gain access to the 32-bit extended registersGain access to the 32-bit extended registers




In our context, things like printers, In our context, things like printers, joysticks, and scanners aren’t peripheralsjoysticks, and scanners aren’t peripherals

Some examples are parallel, serial and Some examples are parallel, serial and USB ports, the internal timers, interrupt USB ports, the internal timers, interrupt controllers, network interface cardscontrollers, network interface cards

Many helper devices inside the processor, Many helper devices inside the processor, on the mother board, or in expansion slotson the mother board, or in expansion slots



Peripheral I/O busPeripheral I/O bus

There is a separate set of address/data busses There is a separate set of address/data busses commonly used for communication with commonly used for communication with peripheral devicesperipheral devices

In reality, they’re the same busses, just different In reality, they’re the same busses, just different signals in the control bus cause different things signals in the control bus cause different things to happento happen

The I/O address bus is 16-bits wide, meaning The I/O address bus is 16-bits wide, meaning you can address 65,535 different I/O ports.you can address 65,535 different I/O ports.

The I/O data bus is 16-bitsThe I/O data bus is 16-bits



Peripheral I/OPeripheral I/O

Peripheral devices don’t Peripheral devices don’t havehave to use the to use the I/O bus. They can be memory mapped.I/O bus. They can be memory mapped.

Video cards are an exampleVideo cards are an example

They have a large amount of memory They have a large amount of memory (VRAM) and that is typically mapped to a (VRAM) and that is typically mapped to a range of addresses in the memory spacerange of addresses in the memory space



Peripheral examplePeripheral example

Network cardNetwork card

Input/Output Range Input/Output Range CC00-CC7FCC00-CC7F

Memory Range Memory Range FB000000-FB00007FFB000000-FB00007F

This one is both This one is both memory mapped memory mapped andand I/O mappedI/O mapped




All this really means to you is that All this really means to you is that sometimes you’ll use one set of sometimes you’ll use one set of instructions to access a device, and instructions to access a device, and sometimes you’ll use a different set.sometimes you’ll use a different set.

We’ll talk about this again when we cover We’ll talk about this again when we cover serial/parallel ports, timers, interrupts, and serial/parallel ports, timers, interrupts, and the video graphics adapter.the video graphics adapter.



Instruction processingInstruction processing

Processing of an instruction by the Processing of an instruction by the microprocessor consists of three basic steps microprocessor consists of three basic steps

1.1. fetch instruction from the memoryfetch instruction from the memory2.2. decode the instructiondecode the instruction3.3. execute (usually involves accessing the memory for execute (usually involves accessing the memory for

getting operands and storing results)getting operands and storing results)

Operation of an early processor like the Intel Operation of an early processor like the Intel 80858085

Fetch1

Decode1

Execute1

Fetch2

Decode2

Execute2

…...

Busy Idle Busy …...Busy Idle Busy

Microprocessor

Bus



Instruction processingInstruction processing

Fetch1

Fetch2

Fetch5

Fetch3

Fetch4

Modern microprocessors can process several instructions Modern microprocessors can process several instructions simultaneously at various stages of executionsimultaneously at various stages of execution

this ability is called pipeliningthis ability is called pipelining

Operation of a pipelined microprocessor like the Intel 80486Operation of a pipelined microprocessor like the Intel 80486

Store1

Fetch6

Fetch7

Read2

Decode1

Decode2

Decode3

Decode4

Decode5

Decode6Idle Idle

Execute1 Idle

Execute2

Execute3

Execute4

Execute5

Execute6

GenerateAddress

1

GenerateAddress

2

Bus Unit

Instruction Unit

Execution Unit

Address Unit

Modern microprocessors can process several instructions Modern microprocessors can process several instructions simultaneously at various stages of executionsimultaneously at various stages of execution

this ability is called pipeliningthis ability is called pipelining

Operation of a pipelined microprocessor like the Intel 80486Operation of a pipelined microprocessor like the Intel 80486




Everything in your assembly file is one of Everything in your assembly file is one of the following:the following: A commentA comment A labelA label An instruction or directiveAn instruction or directive DataData



Assembly primer - commentsAssembly primer - comments

; Comments are denoted by semi-colons.; Comments are denoted by semi-colons.

; These are comments!!! Yeah!!!.; These are comments!!! Yeah!!!.

; Please comment your MP’s thoroughly.; Please comment your MP’s thoroughly.

; It helps us figure out what you were doing; It helps us figure out what you were doing

; It also helps you figure out what you were; It also helps you figure out what you were

; doing when you look back at code you; doing when you look back at code you

; wrote more than two minutes ago.; wrote more than two minutes ago.




You might be asking, “What about You might be asking, “What about variables? Why aren’t they on the bulleted variables? Why aren’t they on the bulleted list?”list?”

Variables are nothing more than labels Variables are nothing more than labels that mark specific memory locationsthat mark specific memory locations

Labels can also mark the beginning of Labels can also mark the beginning of procedures or “jump to” locations in your procedures or “jump to” locations in your codecode



Assembly primer - labelsAssembly primer - labels

; Labels can be global; Labels can be global

MyGlobalLabel:MyGlobalLabel:

MyOtherGlobalLabelMyOtherGlobalLabel

; They can be local too; They can be local too

.MyLocalLabel.MyLocalLabel

; Local labels are good only back to the ; Local labels are good only back to the previous un-dotted labelprevious un-dotted label



Assembly primer - labelsAssembly primer - labels

MyBigGlobalLabelMyBigGlobalLabel

.local_label1.local_label1

.local_label2.local_label2

MyNextBigGlobalLabelMyNextBigGlobalLabel

.local_label1.local_label1 ; these are distinct; these are distinct

.local_label2.local_label2 ; to the ones above; to the ones above



Assembly primer - variablesAssembly primer - variables

; Let’s do something with labels now; Let’s do something with labels now

VAR1 DB 255VAR1 DB 255

VAR2 DB 0FFhVAR2 DB 0FFh

VAR3 DW 1234hVAR3 DW 1234h

ARR1 DB 12, 34, 56, 78, 90ARR1 DB 12, 34, 56, 78, 90

ARR2 DW 12, 34, 56, 78, 90ARR2 DW 12, 34, 56, 78, 90

STR1 DB ‘291 is awesome!!!’, 0STR1 DB ‘291 is awesome!!!’, 0

BUF1 RESB 80BUF1 RESB 80

labels directives data



Assembly primer - directivesAssembly primer - directives

EXTERN – allows you to declare external EXTERN – allows you to declare external procedures so you can use them in your procedures so you can use them in your program.program.SEGMENT – lets you declare the SEGMENT – lets you declare the beginning of a memory segment. We’ll beginning of a memory segment. We’ll talk in detail about memory segments talk in detail about memory segments tomorrow.tomorrow.EQU – lets you define pre-processor EQU – lets you define pre-processor constants.constants.



Assembly primer - directivesAssembly primer - directives

; Let’s declare some external functions; Let’s declare some external functionsEXTERN kbdine, dspout, dspmsg, dosxitEXTERN kbdine, dspout, dspmsg, dosxit

; Let’s begin our code segment; Let’s begin our code segmentSEGMENT codeSEGMENT code

; I’d normally put my variables right here; I’d normally put my variables right here

..start..start ; This is a special label that; This is a special label that; denotes the execution starting; denotes the execution starting; point. The next instruction; point. The next instruction; after ..start will be the first; after ..start will be the first; to run when you execute your program; to run when you execute your program



Assembly primer - instructionsAssembly primer - instructions

; Here are some simple instructions; Here are some simple instructions

mov ax, [VAR1] ; notice the bracketsmov ax, [VAR1] ; notice the brackets

mov dx, STR1 ; notice the not bracketsmov dx, STR1 ; notice the not brackets

call dspmsgcall dspmsg

jmp donejmp done

mov bx, [VAR2] ; this will never happenmov bx, [VAR2] ; this will never happen

donedone



ExampleExample

SEGMENT codeSEGMENT codevar1var1 dbdb 55h55h ; 55; 55var2var2 dbdb 0AAh0AAh ; AA; AAvar3var3 dbdb 12h12h ; 12; 12str1str1 dbdb "Hello", 0"Hello", 0 ; 48 65 6C 6C 6F 00; 48 65 6C 6C 6F 00

..start..startmovmov al,al, [var1][var1] ; A0 00 00; A0 00 00movmov bx,bx, var3var3 ; BB 02 00; BB 02 00incinc bxbx ; 43; 43movmov al,al, [bx][bx] ; 8A 07; 8A 07



AssignmentsAssignments

Keep working on MP0 and HW0Keep working on MP0 and HW0

Documents

ECE291 Lecture 1 All about computers. ECE 291 Lecture 1Page 2 of 41 Lecture outline Top-down view of computers Processor architecture RegistersMemoryPeripherals