Parts for computers

*CPU, Monitor,Mouse, Keyboard, Sound Box

Extra- UPS,Printer,Scanner (ETC)

What is CPU?

Æ It is the part of the computer that actually processes the data.

            The CPU

Æ ‘Brain’ or ‘heart’ of the computer

Æ Accepts data and instructions from the input device (or from the software stored in its memory).

Æ Processes the data according to the given instructions.

Æ Finally stores the results of the operations in its memory or displays it in a suitable output media such as monitor, printer etc.

What is Processing?

ÆThe procedure that transforms raw data into useful information is called processing.

           ÆTwo components handle processing in a computer:

1.     processor (CPU)

2.     memory.

A Computer System Architecture

Basic Computer Architecture

1. Computer systems comprise

The Central Processing Unit

2. It has two basic part:

                  ÆControl unit

                  ÆArithmetic logic unit

3. Also provide memory (Registers)

peripheral devices

4. The devices that supply information to the CPU, and give the results to the outside world
5. Analogous to human senses, and memory aids such as books, etc.
6.  

System Diagram

CPU Components

•        CPU Components

Æ CU: Control Unit

•        interprets stored instructions in sequence

•        issues commands to all elements of the computer system

Æ ALU: Arithmetic & Logic Unit

•        performs arithmetic and logic instructions

•        Traditionally the CPU also included

RAM: Random Access Memory

•        holds data, instructions and results of processing

•        temporary (volatile)

•        Often, CPU is used to mean just the CU and ALU

the ‘processor’ or ‘microprocessor’

CPU Diagram

Machine Cycle

•        Machine cycles

ÆSteps by CPU to process data

ÆCan be divided into two parts:

•        Instruction cycle

ÆCPU gets the instruction

•        Execution cycle

ÆCPU performs the instruction

                  Æ Billions of cycles per second

ÆPipelining processes more data

ÆMultitasking allows multiple instructions

Affecting Processing Speed

•        Registers

•        Virtual RAM

•        The computer’s internal clock

•        The bus

–       External bus standards

•        Peripheral control interface (PCI)

•        Accelerated Graphics Port (AGP)

•        Universal Serial Bus (USB)

•        PC Card

Cache memory

•        Cache memory

> Very fast memory

> Holds common or recently used data

> Speeds up computer processing

> Most computers have several caches

•        L1 holds recently used data

•        L2 holds upcoming data

•        L3 holds possible upcoming data

Processor Types

•        There are many different manufacturers of microprocessors, often incompatible

> Intel

•        8080, 8088, 80186, 80286, 80386, 80486

•        Pentium, Pentium Pro, II / III / MMX, etc.

> AMD

•        make Intel compatible processors for PC’s

> Motorola

•        68xxx family

•        used in Apples

> IBM, DEC (VAX), Zilog, Cyrix (owned by VIA)

•        specialist companies making dedicated processors

CISC

•        It was originally assumed that in order to make a microprocessor better (quicker, more powerful), it was necessary to add more and more instructions

* Complex Instruction Set Computer

•        A CISC microprocessor has a large instruction set, with many complex instructions

* Intel

•        8086 - 80686 (Pentium Pro / II / III / IV)

* Motorola

•        68000 - 68070

RISC

•        Most programs only use a few instructions

* optimise the processor for these ‘key’ instructions

* Reduced Instruction Set Computer

•        RISC

* very fast, due to fewer instructions

* less transistors, so simpler & cheaper to manufacture

* but, software has to work harder to make up the ‘missing’ instructions

* examples

•        DEC alpha AXP, Sun (Ultra) Spars, Motorola 60x, IBM RISC6000

•        widely used in Acorn’s PC’s, e.g. Archimedes

•        Pentium IV, Crusoe

Number Systems

•        To talk about binary data, we must first talk about number systems

•        The decimal number system (base 10) you should be familiar with

* A digit in base 10 ranges from 0 to 9.

* A digit in base 2 ranges from 0 to 1 (binary number system).  A digit in base 2 is also called a ‘bit’.

* A digit in base R can range from 0 to R-1

* A digit in base 16 can range from 0 to 16-1 (0,1,2,3,4,5,5,6,7,8,9,A,B,C,D,E,F).  Use letters A-F to represent values 10 to 15.  Base 16 is also called Hexadecimal or just ‘Hex’.

Positional Notation

•        Value of number is determined by multiplying each digit by a weight and then summing. The weight of each digit is a POWER of the BASE and is determined by position.

•         953.78 =   9 x 102 + 5 x 101 + 3 x 100 + 7 x 10-1 + 8 x 10-2
                   = 900 + 50 + 3 + .7 + .08 =  953.78 

•         1011.11  =   1x23 + 0x22 + 1x21 + 1x20 + 1x2-1 + 1x2-2
                         =   8 +0 + 2+1+ 0.5  + 0.25
                     =  11.75

•         A2F   =   10x162 + 2x161 + 15x160
                  =   10 x 256+2 x 16+15 x 1
              =  2560 + 32 + 15 =  2607