Cpu and Memory

7/27/2019 Cpu and Memory

1/76

Introduction to CPU

Brief History of the CPU

Main Components and Structure of the CPU

Computer Bus Overview

Single Bus Architecture

Overview of Assembly ProgrammingMicroprogramming

Gating and Control Sequencing

Cache Memory

Virtual Memory

Memory Interleaving


2/76

In order to work, a computer needs some

sort of "brain" or "calculator". At the core of

every computer is a device roughly the size

of a large postage stamp.

This device is known as the central

processing unit, or CPU for short. This is the

"brain" of the computer; it reads andexecutes program instructions, performs

calculations, and makes decisions.


3/76

The CPU is responsible for storing and

retrieving information on disks and other

media.

It also handles information on from one part

of the computer to another like a central

switching station that directs the flow of

traffic throughout the computer system.


4/76


5/76

The CPU resides inside a box known as the systemunit, along with various support devices and tools

for storing information. The system unit case, that is the metal case itself,

can either be short and wide, in which case itusually sits on top of your desk, often underneath

the screen (left image), or it can be taller andnarrow, in which case it generally sits underneathyour desk and is referred to as a tower case (rightimage).


6/76

CPU history starts in 1971, when a smallunknown company, Intel, for the first timecombined multiple transistors to formacentral processing unit - a chip called

Intel 4044. However, it was 8 years beforethe first Personal Computer was constructed.

PC's are designed around different CPUgenerations. Intel is not the only company

manufacturing CPU's, but by far the leadingone. The following table shows the differentCPUgenerations. They are predominantlyIntel chips, but in the 5th generation we seealternatives.


7/76

PC CPU's Year Number of Transistors1st Generation 8086 and 8088 1978-81 29,0002nd Generation 80286 1984 134,0003rd Generation 80386SX and 80386DX 1987-88 275,0004th Generation 80486SX, 80486DX, 80486DX2 and

80486DX4 1990-92 1,200,0005th Generation Pentium

Cyrix 6x86

AMD K5

IDT WinChip C6

1993-95

1996

1996

1997

3,100,000

--

--

3,500,000Improved 5th GenerationPentium MMX

IBM/Cyrix 6x86MX

IDT WinChip2 3D1997

1997

19984,500,000

6,000,000

6,000,0006th Generation Pentium Pro

AMD K6

Pentium IIAMD K6-2

1995

1997

19971998

5,500,000

8,800,000

7,500,0009,300,000

Improved 6th GenerationMobile Pentium IIMobile Celeron

Pentium III

AMD K6-3

Pentium III CuMine

1999 27,400,00018,900,000

9,300,000

--

28,000,000-


8/76

What does the CPU do?

Carries out instructions and tells the rest of the

computer system what to do.

This is done by the Control Unit of the CPU whichsends command signals to the other components of

the system.

Performs arithmetic calculations and data

manipulation, eg. comparisons, sorting, combining,

etc. The computer's calculator is a part of the CPUknown as theArithmetic Logic Unit.

Holds data and instructions which are in current use.

These are kept in theMain Store orMemory.


9/76


10/76

directs the entire computer system to carry

out stored program instructions.

must communicate with both the arithmeticlogic unit and main memory.

uses the instruction contained in

the Instruction Register to decide whichcircuits need to be activated.


11/76

co-ordinates the activities of the other two

units as well as all peripheral and auxiliary

storage devices linked to the computer.

instructs the arithmetic logic

unit which arithmetic operations or logical

operation is to be performed.

is literally in control.


12/76

Specialized electronic circuitry in the control

unit is designed to decode program instructions

held in the main memory. Each instruction isread from the memory into the instructionregister. The process of reading an instruction isoften referred to as thefetch-execute process.


13/76

executes arithmetic and logical operations.

Arithmetic operations include addition,subtraction, multiplication and division.

Logical operations compare numbers, lettersand special characters.

Comparison operations test for three conditions:

Equal - to condition in which two values are thesame

Less - than condition in which one value is smallerthan the other

Greater - than condition in which one value is largerthan the other


14/76

Relational operations (=, ) are used to

describe the comparison operations used by

the arithmetic logic unit.

The arithmetic logic unit performs logic functions such

as AND, OR and NOT.


15/76

The Computer bus is a group of parallel wires

that is a path or route between the different

interconnecting components of a computer

system.

The two main buses in a computer are the

internal or system bus and external or theexpansion bus.


16/76

The expansion bus connects externaldevices such as mouse, printer, keyboard or

modem to the CPU, while the system busconnects the CPU to other devices that

resides on the motherboard

The system bus has two parts.

Data bus

Address bus


17/76

Industry Standard Architecture (ISA) bus isused in many computers to connect slower

devices such as modem and other input

devices.

Universal Serial Bus (USB) is a hotswappable bus which means that a computer

user can connect then disconnect a USB

device without affecting the PC or laptop. Local bus is designed to attach faster

devices to the CPU.


18/76

Accelerated Graphics Bus or Port (AGP Bus)allows the video card to access the RAM directly,

thus increasing the speed of graphics

performance for 3-D(Dimensional) and full

motion video applications.

PC Card Bus is used exclusively on laptopcomputer and is used as network cards, external

modem Wi-Fi Card, thumb scanner and biometric

security system. FireWire (IEEE 1394) bus is used to connect

digital and video cameras. We can use the

FireWire bus to transfer data in high speed rate.


19/76

Single Bus

Slow Performance


20/76

Example of Triple

Bus Architecture


21/76


22/76

High-level programming

- simple code can be easy-to-interpret:

total := subTotal + salesTax

put Hello World!

for count:1..10

put count

end for


23/76


24/76

Each machine language line of code has 2 parts:

- op-code describes the operation to be done

- operand identifies the quantity to be operated

on

All commands are in binary, shown grouped as

hexadecimal digits (4 binary digits = 1 hex digit)

Still quite difficult to read and understand

Good applications of binary/hex number systems

and conversions


25/76

Assembly language uses alpha-numeric charactersand more closely resembles English words oracronyms.

e.g. Move immediate the value 33 into register A

in machine language 3E 33

in assembly language MVI A 33

MVIMoVe Immediate


26/76

Intel released several 8-bit microprocessors in the1970s including the 8080, 8085, 8088.

Simulating a simple processor allows us to show the

steps, registers, process in a scaled-down

environment.

Choose a processor and a corresponding assemblylanguage that suits your needs and has the

resources you need. (8085 used in profiles and here)


27/76

A Register (Accumulator)

B Register

C Register

D Register

E Register

H Register

L Register

SR (Status Register)

PC (Program Counter)

SP (Stack Pointer)

8085CPU

Registers


28/76

MVI Put a specified value in a specified register.

e.g. MVI A B8 - put B8 in A register

MVI B 5F - put 5F in B register


29/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

MVI A B8

B 8


30/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

MVI B 5F

5 F


31/76


32/76


33/76

MVI A 33

INR A

STA 12C3

HLT


34/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

MVI A 33

3 3


35/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

INR A

3 4


36/76


37/76

LDA 55C1

SUI 10

STA 55C1

HLT

- for this example, let's suppose 55C1 starts with thevalue 6A

55C1


38/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

LDA 55C1

6 A

55C1


39/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

SUI 10

5 A


40/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

STA 55C1HLT

5 A

55C1


41/76

Immediate operand is a specific numerical value,

not an address in RAM

e.g. MVI B 52

ADI 22

SUI FF


42/76


43/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

LXI D 3F67

3 F

6 7


44/76

Direct operand represents an address in RAM

(address bus is 16 bits or 2 Bytes)

e.g. LDA 55A2

STA AB31


45/76


46/76


47/76


48/76

A2FF


49/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

LDAX D

A 2

F F

A2FF

? ?


50/76


51/76

MVI A 33

MVI B 89

MVI C 87

STAX B

HLT


52/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

MVI A 33

3 3


53/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

MVI B 89

3 3

8 9


54/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

MVI C 87

3 3

8 9

8 7

8987


55/76


B Register

C Register

D Register

E Register

H Register

L Register



SP (Stack Pointer)

STAX BHLT

3 3

8 9

8 7


56/76

Introduce concept of looping withJMP

Every instruction has a memory location (used by

program counter)

e.g. JMP 0033

- means jump to instruction at memory location 0033

Must keep track of how much space each

instruction requires in order to loop to the right

location


57/76

By comparing two values, we cause flags to be setin the status register. Based on the result of thiscomparison we can decide to loop or not.

1. Compare another register to A.

e.g. CMP C

Sets the flags in the status register as if we weresubtracting contents of C from A. (Does notactually subtract)


58/76


59/76


60/76

MVI A 07

INR A

CPI 0B

JNZ ??

STA 4400

HLT


61/76


62/76


63/76

Process of writing microcode for amicroprocessor.

Microcode is a low-level code that defineshow a microprocessor should function when

it executes machine-language instructions. Typically, one machine-language instruction

translates into several microcodeinstructions. On some computers, the

microcode is stored in ROM and cannot bemodified; on some larger computers, it isstored in EPROM and therefore can bereplaced with newer versions.


64/76


65/76


66/76


67/76

The CPU contains the basic instructions neededto operate the computer, but it cannot sure

entire programs or large sets of data

permanently.

The CPU needs to have millions (or eventrillions, in some computers) of bytes of space

where it can quickly read or write programs and

data while they are being used.

This area is called memory, and it consistseither on the motherboard or on small circuit

board attached to the motherboard. It allows the

CPU to store and retrieve data quickly


68/76

Volatile (Nonpermanent)

Requires power to store data.

Loses its contents when the computers power is

shut off.

The volatile memory in a computer is calledrandom access memory (RAM)

RAMs job is to hold programs and data while

they are in use.

Physically, RAM consists of chips on a smallcircuit board


69/76

Single in-line memory modules (SIMMs) andDual in-line memory module (DIMM)

Are chips found in desktop computers.

Small Outline DIMM (SO-DIMM)

Are chips found in laptop computers.


70/76

Non-Volatile (Permanent

Memory chips that hold data even when the computer is

turned off.

Putting data permanently into this kind of memory is

called burning in the data

Read-only memory (ROM), the data in these chips is onlyread and used not changed.

Programmable read only memory (PROM), chips are oftenfound on hard drives and printers. They contain the

instructions that power the devices.


71/76

o Basic input output system (BIOS), set of start-up

instructions. In addition to booting the machine,BIOS contains another set of routines which ensure

that the system is functioning properly and all

expected hardware devices are present. This

routines is called the power on self test (POST)

Flash memory is a special type ofnonvolatile memory. Examples are digital

cameras, portable MP3 players, flash drives

etc.


72/76

Moving data between RAM and the CPUsregisters is one of the most time-consuming

operations a CPU must perform, simply

because RAM is much slower than the CPU.

A partial solution to this problem is to

include a cache memory in the CPU.

Cache (pronounced cash) memory is similar

to RAM except that it is extremely fastcompared to normal memory and it is used in

a different way.


73/76

When a program is running and the CPUneeds to read a piece of data or program

instructions from RAM, the CPU checks first

to see whether the data is in cache memory.

If the data is not there, the CPU reads thedata from RAM into its registers, but also

loads a copy of the data into cache memory.

The next time the CPU needs the data, it

finds it in the cache memory and saves thetime needed to load the data from RAM


74/76

Cache is present in several places in acomputer. Without cache, your computerwould be a much slower device.

Since the late 1980s, most PC CPUs have had

cache memory built into them. This CPU-resident cache is often called Level-1 (L1)cache. Today, many CPUs have as much as256KB built in.

To add even more sped to modern CPUs, anadditional cache is added to CPUs. Thiscache is called Level-2 (L2) cache. Thiscache used to be found on the motherboard.


75/76

Many PCs being sold today have 512 KB or1024 KB of motherboard cache memory;

higher-end systems can have as much as 2MB

of L2 cache.

In addition to the cache memory built into

the CPU, cache is also added to the

motherboard. This motherboard-resident

cache is now called Level-3 (L3) cache. L3cache is found on very-high-end computers.

It is not necessary for a computer to have L3

cache.


76/76

L1, L2, and L3 all speed up the CPU,although in different ways.

L1 cache holds instructions that have

recently run.

L2 cache holds potential upcoming

instructions.

L3 holds many of the possible instructions.

In all cases, the cache memory is faster forthe CPU to access, resulting in a quicker

program execution.

Documents

Cpu and Memory