Tushar B Kute,Department of Information Technology,

Sandip Institute of Technology and Research Centre, Nashik

Internal Components of PC

Overview• 1. Inside a PC• 2. The Motherboard• 3. RAM• 4. ROM• 5. CMOS Memory• 6. The CPU• 7. Expansion Slots

types of memory

the 'brains'

the processor

Powersupply

CD-ROM drive

Floppydisk drive

Hard disk drive

Wires andribbon cables

Sound/networkcards

1. Inside a PC

Motherboard

• The most important part of a PC is the motherboard. It holds:– the processor chip– memory chips– chips that handle input/output (I/O)– the expansion slots for connecting peripherals

• Some chips are soldered onto the motherboard(permanent), and some are removable (so they can be upgraded).

2. The Motherboard

Motherboard Determines:

• CPU type and speed• Chipset• Secondary cache type• Types of slots• Number of slots• Type of memory

• Number of memory sockets and maximum memory

• Type of case • ROM• Plug & Play

compatibility• Type of keyboard

TRACES –

Thin conductors or circuits on the motherboard that work together for a specific purpose.

Transmit electrical signals to and from CPU, RAM, and Devices

What are Traces?

Form Factors

• Form factor means the size and shape of the actual motherboard

• 3 most common Form Factor classifications:– Baby AT– ATX – Slimline NLX

Physical Form Factors

• Personal Computer – Extended Technology (PC-XT)

– Introduced by IBM, 8088 microprocessor was used.

– It has socket for the processor and chips

Physical Form Factors• AT and Baby AT

– To overcome the problem created by AT Form factor, the Baby AT form factor was introduced.

– Baby AT is designed to hold the peripheral devices like keyboard, video and mouse.

– It could not accommodate the combination of processor, heat sink and fan. Cooling

Physical Form Factors

• ATX and Micro ATX form factor

– Here expansion slots were placed on separate riser cards.

– It provides software controlled shut down and power up.

• Micro ATX form factor – More space for I/O connectors was

provided at the rear end.

Physical Form Factors• LPX and Mini-LPX

– It has sound and video to be integrated on to the motherboard.

– It is not suitable for upgrading and offers poor cooling.

• NLX– Small in size– Suited for low profile desktop

cases

• A chip (microchip) is an integrated circuit - a thin slice of silicon crystal packed with microscopic circuit elements– e.g. wires, transistors,

capacitors, resistors

A Chip

Random AccessMemory (RAM)chips.

Expansion slots

Motherboard Picture

Read-onlyMemory (ROM)chips

Processor chip(the CPU)

• A data bus (a data path): connects the parts of the motherboard.

Moving Data

RAM

via expansion cards

• Random Access Memory (RAM).• RAM is used to hold programs while they ar

e being executed, and data while it is being processed.

• RAM is volatile, meaning that information written to RAM will disappear when the computer is turned off.

3. RAM

• RAM contents can be accessed in any (i.e. random) order.

• By contrast, a sequential memory device, such as magnetic tape, forces the computer to access data in a fixed order because of the mechanical movement of the tape.

Each RAM locationhas an address and holds one byte of data (eight bits).

RAM Storage

• Computers typically have between 64 and 512 Mb (megabytes) of RAM.

• RAM access speeds can be as fast as 8 nanoseconds (8 billionth of a second).

• The right amount of RAM depends on the software you are using.

• You can install extra RAM.

How much RAM is Enough?

• Virtual memory uses part of the hard disk to simulate more memory (RAM) than actually exists.

• It allows a computer to run more programs at the same time.

• Virtual memory is slower than RAM.

Virtual Memory

• Read-Only Memory can be read but not changed.

• It is non-volatile storage: it remembers its contents even when the power is turned off.

• ROM chips are used to store the instructions a computer needs during start-up, called firmware.

• Some kinds of ROM are PROM, EPROM, EEPROM, and CD-ROM.

4. ROM

• A computer needs a semi-permanent way of keeping some start-up data– e.g. the current time, the no. of hard disks– the data may need to be updated/changed

• CMOS memory requires (very little) power to retain its contents.– supplied by a battery on the motherboard

5. CMOS Memory

the battery

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6. The CPU

• The Central Processing Unit (CPU) is the chip on the motherboard that acts as the "computer's brain" – it does calculations, and coordinates the other

motherboard components– CPU examples: the Pentium, the PowerPC chip

• The CPU is also known as the processor or microprocessor.

Some Processors (CPUs)

PowerPC Chip

Chip Fan

Pentium Chip

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The CPU and RAM

The CPUprocesses data.

The RAMcontains dataand programs.

The data bus transports theprocessed data to the RAM soit can be stored, displayed, oroutput.

The CPU in Action

The CPU

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• The instruction pointer in the CPU's control unit stores the location of the next program instruction to be executed.

• The instruction is loaded into the instruction register to be carried out.– registers are local memory on the CPU

continued

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• The ALU (arithmetic logic unit) executes the instruction.

• The result is placed in the accumulator (another register), then stored back in RAM or used in other CPU operations.

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• The system clock sends out 'ticks' to control the timing of all the motherboard tasks– e.g. it controls the speed of the data bus and the

instruction cycle.

• The time it takes to complete an instruction cycle is measured in megahertz (MHz).– 1 MHz = one million cycles per second

The System Clock

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• Word size: the number of bytes the CPU can process at once.– depends on the number of registers in the CPU;– depends on the size of the data bus

• Cache size: the cache is high-speed memory on the CPU that stores data which is needed often.

Two Measures of CPU Size

The expansion bus transports data through the motherboard.

Most expansion cardscontain a port.

A connector cable plugsinto the port, and leads to a peripheral.

7. Expansion Slots

Data originatesin RAM

Expansion slot containing an expansion card.

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• Common expansion cards: – graphics card (for connecting to a monitor)– network card (for transmitting data over a

network)– sound card (for connecting to a microphone and

speakers)

• Most PCs offer 4-8 expansion slots.

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• There are several different types of expansion slot:– ISA: older technology, for modems and slow

devices– PCI: for graphics, sound, video, modem or

network cards– AGP: for graphics cards

Expansion Slot Types

PC Bus• PC bus is an 8 bit expansion slot to connect 8 bit expansion

cards.

Industrial Standard Architecture (ISA) Bus

– ISA bus is a 16 bit slot present in 80286, 80386, 80486 and Pentium systems.

– The ISA card is configured through jumpers or switches

Enhanced ISA

– It is a 32 bit bus.

– Capable of using multiple bus mastering devices.

– Compatible 8 bit PC bus, 16 bit ISA bus.

– Software setup capability for boards

Video Electronics Standard Architecture (VESA) bus – It is a 32 bus. – It is used to connect video cards, I/O cards and

multimedia expansion cards

• Disadvantages of the VESA– 80486 dependence – Limited number of slots – No bus mastering– Boards are configured through jumpers

Topic 6 - Peripheral Component Interconnect (PCI) bus

• PCI– Operates at a speed of 33 MHz or 66

MHz– It is a 64 bit bus – Communicates with processor using a

bridge circuit.

• PCI-X– Operates at 133 MHz bus speed– Offers 64 bit Band width– Supports 1 GB/Sec data transfer rate– Supports efficient bus operation– Provides backward Compatibility

AGP Bus – It is designed for connecting video cards. – PCI bus with 2.1 version at 66MHZ is the basis for

AGP slot. – It supports a new technique called texture cache.

Audio Modem Raiser and Communication Network Raiser

– This specification developed by Intel. – The function of the modem and the analog I/O audio circuitry are

combined together on a small circuit board – The small circuit board is called raiser card – The AMR card enhances the performance by providing better quality

audio solutions.

Connector Cables

References

• “Microprocessors and Interfacing” by Douglas Hall, Tata McGraw Hill Publishing.