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Presented By:

ASAJD JAMSHED(www.asjad.vze.com)

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System Units

http://www.build-your-own-computers.com/best-pc-barebone-kitshttp://www.build-your-own-computers.com/best-pc-barebone-kits

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System UnitSystem Unit The System Unit is a case which is just like a box made up of a

metal or plastic. This casing actually contain the electroniccomponents of a computer used to process data.

The casing is some time called Chassis, that protect the internalelectronic components from damage.

The most important component of this System box is MotherBoard. All the components are then installed on this MotherBoard.

System Unit consist of the following devices:- Mother Board

Processor Memory Display cards Disk systems

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System Unit (Contd)System Unit (Contd)

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Mother BoardMother Board

It is the main circuit board of the system unit. It is the centralized platform where all the hardware

components of a computer are connected. Many electronic components are attached to the mother board,

others are built-in on it. It is sometime called system board. The processor, memory & the other components on the

motherboard consist one or more chips. Most chips are notbigger than one-half inch square.

Each and every Motherboard has a small battery cell. It gives to Motherboard a small amount of power to remember

the settings such as hardware configurations, date and time etc

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Mother Board (Contd)Mother Board (Contd)

BIOS is kind of software which holds the most important datafor machine.

It informs the PC about the compatibility of Motherboard withdifferent hardware components such as CPU etc

It is the most important component which resides in the ROM(Read Only Memory) of the Motherboard.

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ProcessorProcessor The Processor is also called Central Processing Unit (CPU). All the CPUs looks very similar, but they are different in the way,

they have different numbers of pins and different layouts.

The processor significantly impact over all computing power &manages most of computer operations.

On larger computers, such as Mini or Mainframe computers, thevarious functions performed by the processor extend over many

separate chips and often on multiple circuit boards. On a personal computer, all function of the processor usually are ona single chip.

Some computer manufacturer use the term Microprocessor whichrefers to a personal computer chip.

Most PCs today use processors manufactured by IntEL, AMD etc..

Central Processing Unit (CPU) is an electronic device that interprets

and carries out the instructions that operates the computer.

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Processor (Processor (ContdContd))

The combination of Arithmetic Logic Unit and Control Unit iscalled as Central Processing Unit (CPU). OR The two main partsof CPU are ALU & CU.

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Processor (Processor (ContdContd))

ARITHMETIC LOGIC UNIT (ALU) This component of the computer is responsible for

the actual processing.

This component is capable to perform all types ofarithmetic operations such as addition,subtraction, multiplication and division etc.

Also it is capable to perform logical operationssuch as AND, OR etc. it is capable of comparisonas well.

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Processor (Contd)Processor (Contd)

CONTROL UNIT (CU) This unit is responsible for the overall supervision of the

computer system. It does not perform the actual processing but by reading and

interpreting the instructions contained in a program, Control Unit(CU) directs other unit of the system to perform a specific task. Control unit (CU) behaves like a traffic police instructor. It

manages the functions performed by different parts of computer. It controls and coordinates the entire computer system, just the

brain directs the human body. It is responsible to accept data from input device and send it to

the memory, from memory to ALU, finally CU sent back theresults and store in the memory, until the results are released toan output device.

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Memory It is also called Main memory or Primary memory. Memory contains one or more sets of chips that store

data/program instructions, either temporarily or permanently . The component which provides storage capability to a computer

is called Memory. It enables a computer to store data and instructions which are

necessary for the processing. All the computers which are used today needs memory or

storage capability. All the instructions that a computer followsmust be stored in the memory.

There are two types of Primary Memory. Random Access Memory (RAM) Read Only Memory (ROM)

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Random Access MemoryRandom Access Memory RAM is also called volatile memory and Keeps the information

for a shorter period of time because RAM Lose information ifpowered off or the computer is shutdown.

RAM store data or instructions, the computer then uses theseinstructions to perform any processing work.

The contents of RAM change rapidly and often. Typical ranges 128 MB - 4 GB Random Access means direct access to any part of memory

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Random Access Memory (Contd)Random Access Memory (Contd)

The amount of RAM in a PC has a direct affect on the system'sspeed.

The more RAM a PC has, the more program instructions and datacan be held in memory, which is faster than storage on disk.

More RAM = Better Performance !

There are two types of RAM Dynamic RAM

Static RAM

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Random Access Memory (Contd)Random Access Memory (Contd)

Dynamic RAM Dynamic RAM (DRAM) chips must be recharged with

electricity very frequently, or they will lose their contents.

Static RAM

Static RAM (SRAM) does not need to be recharged as oftenas DRAM, and can hold its contents longer. Another type of RAM, called flash memory, can store its

contents after power is turned off. Flash memory is used indigital cameras to store pictures. OR

Flash memory used in portable digital devices.

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Read Only MemoryRead Only Memory

ROM is non-volatile memory. The kind of memory is generally programmed by manufacturer. It contains information that is permanently stored. The

contents of ROM are set during manufacturing process. Most ofthe ROMs are special purpose memories.

Example of ROM is BIOS (Basic Input Output System).

TYPES OF ROM

PROM (Programmable Read Only Memory) Normally ROMs are not writable but PROMs are writable. Data can

be written to PROMs using special devices. Data once written cannot be removed. Ultraviolet Rays are used to

write data in PROMs. Example: CD-ROM (Compact Disk Read Only Memory). Data on a CD-ROM

can be written through a special device called CD-Writer.

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Cache MemoryCache Memory Cache memory is high-speed memory that holds the most recentdata and instructions that have been loaded by the CPU. Cache is located directly on the CPU or between the CPU and

RAM, making it faster than normal RAM. CPU-resident cache is called Level-1 (L1) cache. L1 cache usually has a very small capacity, ranging from 8 KB to

128 KB. The most common size is 128 KB. External cache is called Level-2 (L2) cache.

L2 cache is slower then L1 cache but has much larger capacity,ranging from 64 KB to 4 MB.

The amount of cache memory has a tremendous impact on thecomputer's speed.

When the processor needs an instruction or data, it searchesmemory in this order, L1 cache, then L2 cache, then RAM.

If the instructions or data is not found in memory then it mustsearch a slower speed storage medium such as a hard disk,compact disc etc.

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Storage DevicesStorage Devices

Storage devices holds data, instructions &information for future use.

Every computer uses storage devices to holdssoftware, specifically system software & application

software's. It is also called Secondary Storage or Auxiliary

Storage Devices. Example of storage media are

Magnetic Storage Devices Hard Disk, Floppy Disk

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Magnetic Storage DevicesMagnetic Storage Devices

Exploits duality of magnetism and electricity Converts electrical signals into magnetic charges Captures magnetic charge on a storage medium Later regenerates electrical current from stored magnetic

charge

Flat, circular platter with metallic coating that is rotatedbeneath read/write heads

Random access device; read/write head can be moved to any

location on the platter

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Magnetic Storage Devices - FormattingMagnetic Storage Devices - Formatting

Formatting is the process of preparing a disk for reading and writing. Before a magnetic disk can be used, it must be formatteda

process that maps the disk's surface and determines how data willbe stored.

During formatting, the drive creates circular tracks around thedisk's surface, then divides each track into sectors.

The OS organizes sectors into groups, called clusters, then trackseach file's location according to the clusters it occupies.

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Hard DisksHard Disks

Auxiliary storage is a hard disk. Hard disks use multiple platters, stacked on a spindle. or A hard disk consists of one or more rigid metal plates coated with a

metal oxide material that allows data to be magnetically recorded onthe surface of the platters.

Each platter has two read/write heads, one for each side. The hard disk platters spin at a high rate of speed, typically 5400 to

7200 revolutions per minute (RPM). Storage capacities of hard disks for personal computers range from 10

GB to 320 GB (TB is possible but rare). Read/write heads

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Hard Disk (Contd)Hard Disk (Contd)

Sectorseach track is divided intopie-shaped wedges

Clustertwo or moresectors combined

Tracksdata is recorded in concentriccircular bands