3 Evolution of Computers Upto 8088

8/22/2019 3 Evolution of Computers Upto 8088

1/26

Evolution of ComputersEvolution of Computers

Up to IBM PC/Intel 8088Up to IBM PC/Intel 8088

By

Prof. Dr. Shaiq A. HaqChairman CSE Department

University of Engineering & Technology, Lahore


2/26

Scheme of PresentationScheme of Presentation

Von Neumann Architecture

Architecture of Intel Microprocessors;

4004 (1971, 4-bit, 4KB address space)




8085 (1975, 8-bit, 5 volt version)

8086/8088 (1978, 16-bit, 1MB address space)


3/26

Von Neumann ArchitectureVon Neumann Architecture

An architecture referred to computing machines in1945, having Memory, Instruction Decoder, Control

Unit, ALU, Data Paths/Bus. The idea of Stored Program was first introduced in

1936 by konrad Zuse in a Patent application but the

credit of architecture goes to Von neumann. Separation of Storage from Processing Unit

Sequential (Fetch-Decode-Execute) cycle

Common bus for instruction and data

A stored-program design also lets programs modifythemselves while running.


4/26

Von Neumann ArchitectureVon Neumann Architecture

The separation between the CPU, Memory and I/O devicesleads to what is known as the von Neumann bottleneck.


5/26

Modern Computer ArchitectureModern Computer Architecture

MemoryMemory(Stored Program Instructions)

InstructionInstructionDecoderDecoder

Control UnitControl Unit

ALU

I/O DevicesI/O Devices

IRIR

PCPC

ACCUMULATOR


6/26

Harvard ArchitectureHarvard Architecture

In Harvard Architecture two separate

memories are used for instructions and data

instead of a single memory.

Harvard Architecture vs. Princeton

Architecture.

Shared Bus Architecture vs. Independent

Bus Architecture.


7/26

Architecture of Intel 4004Architecture of Intel 4004

The Intel 4004, a 4-bit central processingunit (CPU), released by Intel Corp. in 1971,

is widely considered to be the worlds firstcommercial single chip microprocessor.

Based on Harvard Architecture

4-bit data bus, 12-bit program address,which allowed 4 KB memory access from

the 4-bit address bus if all 16 RAMs wereinstalled.

16- registers

8-bit instructions (46 instructions, 5 16-bit)
http://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.png


8/26

Intel 4004Intel 4004

2,300 transistors

16-pin CERDIP

Maximum clock

speed 740 KHz.

A collectors item

In 2006, $1,000per chip on eBay
http://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/1/10/4004_dil.pnghttp://upload.wikimedia.org/wikipedia/commons/b/b4/4004_arch.png


9/26

Intel 4004 ArchitectureIntel 4004 Architecture
http://upload.wikimedia.org/wikipedia/commons/b/b4/4004_arch.pnghttp://upload.wikimedia.org/wikipedia/commons/b/b4/4004_arch.pnghttp://upload.wikimedia.org/wikipedia/commons/b/b4/4004_arch.png


10/26


Introduced in 1972.

8-bit single bus, 18-pin DIP package.

3,300 transistors.

Initial versions of the 8008 ran at 0.5 MHz, later

increased to 0.8 MHz. Although slower than 4004 yet 8008 processed 8-

data bits at a time and could access significantly

more RAM actually gave it 3 to 4 times the true

processing power of the 4-bit chips.

Intels later CISC design heavily based on 8008.


11/26


The Intel 4040 microprocessor was the successorto the Intel 4004. It was introduced in 1974.

The 4040 was used primarily in games, test,development, and control equipment.

The package of the 4040 is more than twice as

wide as the 4004 and has 24 pins vs. the 16 of the4004.

The 4040 added 14 instructions, larger stack (8

level), 8K program space, 8 more registers, andinterrupt abilities (including shadows of the first 8registers).


12/26


First truly usable microprocessor CPU design.

This 8-bit CPU was released in April 1974.

Clock speed 2 MHz. Available in 40-pin DIP. Used the same instruction set of 8008.

8-bit data bus, 16-bit address bus (64KB)

Seven 8-bit registers, six of which could becombined into three 16-bit register pairs (BC, DEand HL). It also had the 8-bit Accumulator, the 16-

bit Stack Pointer to memory (replacing the 8008'sinternal Stack), and a 16-bit Program Counter.

All processor commands were coded by one byte,but some of them were followed by one or two bytes

of data, a memory address, or a port number.


13/26


The 8080 IC was manufactured by NMOS

technology using a pitch of 6m.

About 6,000 transistors, die size 20mm2.

This CPU formed the basis of computers

running CP/M operating system (just like

8088 and DOS combination in 80s).


14/26


Introduced in 1975, binary compatible with

8080.

The "5" in the model number came from the

fact that the 8085 required only a +5 volt

power supply rather than the +5V, -5V and+12V supplies the 8080 needed.

Available in 40-pin DIP. 8-bit data bus, 16-bit address bus.


15/26

MooreMoores Laws LawAfter every 18 months the number of transistors on a chip doubleAfter every 18 months the number of transistors on a chip double..


16/26

Intel 8086/8088 MicroprocessorsIntel 8086/8088 Microprocessors

Intel 8086 and 8088 Microprocessors are

the basis of all IBM-PC compatible

computers (8086 introduced in 1978, first

IBM-PC released in 1981)

All Intel, AMD and other advancedmicroprocessors are based on and are

compatible with the original 8086/88. At Power Up and Reset time, Pentiums,

Athlons etc all look like 8086 processors.


17/26

Intel 8086/8088 MicroprocessorsIntel 8086/8088 Microprocessors

Intel 8086 is a 16 bit microprocessor:

16b data registers, 16b ALU

Width of external data bus:

8086: 16 bit

8088: 8 bit Width of external address bus: 16b+4b=20b

Segment: Offset memory model Little-Endian Data Format


18/26

8086/8088 (1)8086/8088 (1)

Original IBM PC used 8088 microprocessor

8088 is similar to the 8086, but it has anexternal 8b data bus & only 4B-deep queue

For cost reduction reasons

We can consider 8086 and 8088 together PC clones often used 8086 for better

performance

8-bit bus reduces performance, but meantcheaper computers


19/26

8086/8088 (2)8086/8088 (2)

Remember the Fetch-Decode-Execute cycle?

Fetching from EXTERNAL MEMORY isSLOW.

The 8086/88 used an instruction queue to

speed up performance.

While the processor is decoding and

executing an instruction, its bus interface canbe reading new instructions, since at that time

the bus is not actually in use.


20/26

8086/8088 (3)8086/8088 (3)

8086/8088 consists of two internal units

The execution unit (EU) - executes the

instructions

The bus interface unit (BIU) - fetches

instructions, reads operands and writes results The 8086 has a 6B prefetch queue.

The 8088 has a 4B prefetch queue.


21/26


Temporary

Registers

ALU

Flags

EUControl

AH AL

BH BL

CH CL

DH DL

SP

BP

DI

BI

CS

DS

SS

ES

IO

InternalCommunications

Registers

SUMMATION

Address Bus 20 bits

Data Bus

BusControl

1 2 3 4

Instruction Queue

8088Bus

EU BIU

I PI P


22/26

BIU ElementsBIU Elements

Instruction Queue: the next instructions or data can befetched from memory while the processor is executingthe current instruction

The memory interface is slower than the processorexecution time so this speeds up overallperformance

Segment Registers:

CS, DS, SS and ES are 16b registers used with the16 bit Base registers to generate the 20b address

Allow the 8086/8088 to address 1MB of memory

Changed under program control to point todifferent segments as a program executes

Instruction Pointer (IP) contains the Offset Address of

the next instruction, the distance in bytes from theaddress given by the current CS register

MAXIMUM

MODE

MINIMUM

MODE


23/26

MODE MODE

1 40

20 21

8086

GND

AD14

AD13

AD12

AD11

AD10

AD9AD8

AD7

AD6

AD5

AD4

AD3

AD2

AD1

AD0

NMI

INTR

CLK

GND

Vcc

AD15

A16,S3

A17,S4

A18,S5

A19,S6

/BHE,S7MN,/MX

/RD

/RQ,/GT0

/LOCK

/S2

/S1

/S0

QS0

QS1

/TEST

READY

RESET

/RQ,/GT1

HOLD

/WR

IO/M

DT/R

/DEN

ALE

/INTA

HLDA


24/26

74LS245

x2

8284A

Clock

Generator

RDY

Vcc

8086

CPU

CLK

READY

RESET

MN/MX#

S0#

S1#

S2#

8288

Bus

Controller

MRDC#MWTC#

AMWC#

IORC#

IOWC#

AIOWC#

INTA#

CLK

74LS373

x3ADDR/DATA

LE

OE#

ALE

DENDT/R#

BHE#

AD15:AD0

A19:A16

74LS245

x2

EN#

DIR

D15:D0

A19:A0,

BHE#

ADDR/Data

INTR

i8086 Circuit - Maximum Mode


25/26

Flag RegistersFlag Registers

The 8086 has 9 flags, the 80286 has 11 flags, and the80386 has 13 flags. All of these flag registers include 6flags related to data conditions (sign, zero, carry, auxiliary

carry, overflow, and parity) and three flags related tomachine operations (Interrupt, Single-step and Strings).The 80286 has two additional flags: I/O Privilege andNested Task. The I/O Privilege uses two bits in protectedmode to determine which I/O instructions can be used, andthe nested task is used to show a link between two tasks.

The processor also includes control registers and system

address registers, debug and test registers for system anddebugging operations.

/


26/26

8086/8088 Summary8086/8088 Summary

First Generation (introduced June 1978)

One of the first 16b processors on the

market

16b internal registers

16/8b external data bus

20b address bus (1MB addressable)

Used in 1st generation IBM PCs (1981)

3 Evolution of Computers Upto 8088

Documents