•INSIDE THE TYPICAL PCINSIDE THE TYPICAL PC

A typical Personal Computer (PC) system unit includes Power Supply, several electronic equipments (Hardware), Disk Drives, and some type of ports for peripheral interface.

• POWER SUPPLYPOWER SUPPLY• In a personal computer (PC), the Power Supply is the metal box usually found

in a corner of the case. Without it, a computer is just an inert box full of plastic and metal. The Power Supply converts the alternating current (AC/120 valts) line from your home to the direct current (DC/3.3, 5, 12 volts) needed by the electronic circuits, disk drive motors, and cooling fans in the PC.

•MOTHER BOARDMOTHER BOARD• The motherboard of any computer is basically the main

circuit board (physical foundation of the computer) that synchronizes the transfer of data between the processor (CPU), the memory, the disk drives, and any input and output devices that the computer system may have.

•MOTHERBOARD STRUCTUREMOTHERBOARD STRUCTURE

• CPU

• RAM

• ROM

• BIOS Chip

• Data Bus

• Expansion Slots

• ISA-PCI-AGP Slots

• IDE Ports & Cables

• Parallel Port

• Serial Port

• USB Port

• Disk Drives

• HD, FD, CD

•CPU (Central Processing Unit)CPU (Central Processing Unit)• Microprocessor executes a collection of machine

instructions that tell the processor what to do. Based on the instructions, a microprocessor does three basic things:

• Using its ALU (Arithmetic/Logic Unit), a microprocessor can perform mathematical operations like addition, subtraction, multiplication and division. Modern microprocessors contain complete floating point processors that can perform extremely sophisticated operations on large floating point numbers.

• A microprocessor can move data from one memory location to another.

• A microprocessor can make decisions and jump to a new set of instructions based on those decisions.

•CPU (Central Processing Unit)CPU (Central Processing Unit)

•RAMRAM• Located inside the system unit are RAM chips. The amount

of RAM determines the maximum size of programs and files that the microcomputer can accept. Common Ram sizes of microcomputers are 64 MB, 128 MB and 256 MB. Ram is also called primary memory and main memory.

• RAM is free of programs and data when the computer is first turned on. When the system is turned on, part of the operating system is loaded into memory. When a program like a word processor is started, it is loaded into RAM also. The document that is created with the word processor is also contained in RAM.

• RAM stores information only while the computer is turned on. If power is lost the information it contains is lost and cannot be recaptured (obtained back). For this reason, RAM is said to be volatile.

•RAMRAM

•ROMROM

• An abbreviation for Read Only Memory. ROM is used to hold programs and data that must survive when the computer is turned off. Because ROM is non-volatile; data in ROM will remain unchanged the next time the computer is turned back on.

• ROM examples: ROM Chip, CD ROM, DVD ROM...

•BIOS CHIPBIOS CHIP• The BIOS software has a number of different roles, but its most

important role is to load the operating system. When you turn on your computer and the microprocessor tries to execute its first instruction, it has to get that instruction from somewhere. It cannot get it from the operating system because the operating system is located on a hard disk, and the microprocessor cannot get to it without some instructions that tell it how. The BIOS provides those instructions. Some of the other common tasks that the BIOS performs include:

•BIOS CHIP (continue)BIOS CHIP (continue)• A power-on self-test (POST) for all of the different hardware

components in the system to make sure everything is working properly

• Activating other BIOS chips on different cards installed in the computer - For example, SCSI and Graphic Cards often have their own BIOS chips.

• The BIOS runs at the startup sequence where it configures devices and then boots the operating system. The function of the BIOS is so vital that the information on the BIOS is stored on a ROM chip separate from the hard drive to protect it from potential crashes.

•THE DATA BUSTHE DATA BUS

• An electrical path to transfer data and instructions back and forth between internal memory devices and the processor.

• Is the pathway of the circuits that connects the CPU with the major components in the system unit, the disk, primary memory, and the expansion slots. A data bus is like a street with multiple lanes for travel.

•EXPANSION SLOTSEXPANSION SLOTS

• The Expansion Slots on the motherboard is used to expand the computer system by adding different types of peripheral devices or components such as Sound Card, Graphic (VGA) Card, Modem, Network Card, TV Card, and so on... and connects these devices to the system through the data bus.

• The major types of the Expansion Slots are the ISA, PCI, and the AGP slots that can be used to expand the computer system. The only difference that these slots have are the number of interconnection legs to the data bus and their data carrying speed through the data bus.

•EXPANSION SLOTSEXPANSION SLOTS

•ISA (Industry Standard Architecture)ISA (Industry Standard Architecture)

• The earliest bus to be developed. It runs at a relatively slow speed of 8.33MHz (compared with PCI and AGP) which is why not many devices are still used on it today. Those devices that still remain are called legacy cards because they are no longer manufactured, and are normally leftovers from old computers.

•PCI (Peripheral Connection Interface)PCI (Peripheral Connection Interface)• After the ISA bus, the PCI bus was developed. This stands

for Peripheral Connection Interface, and runs at the somewhat faster speeds of 33MHz or 66MHz. Most modern expansion cards, such as sound cards, network cards, modems, and television cards use this interface. It is easy to set up, and supports what is known as plug-and-play. This means that you can, in most cases, simply 'plug' the card in, and it will set up itself! This doesn't always work, but even when there are problems, it's still quicker and more reliable than ISA. For this reason, this is the most widely adopted interface that you will find in modern PCs, and if you were to look inside your computer, you would find mostly PCI slots. These are slightly shorter than ISA slots, and are colored white. A lot of graphics cards still use the PCI bus, but for cards that need the fastest performance (such as for games and CAD - Computer Aided Design - software), a whole new bus has been developed, called AGP.

•AGP (Advanced Graphics Port)AGP (Advanced Graphics Port)• AGP was developed by Intel as a way to enhance the

performance and speed of the graphics hardware connected to a PC. While AGP is based on the PCI Bus, and is often referred to as the "AGP bus," it is not actually a bus system. Instead, it is a point-to-point connection. In other words, the only device connecting through AGP to the CPU and system memory is the graphics card. There are no other "stops" to make on the path. Therefore, it is not truly a bus.

• AGP provides two major enhancements over PCI: • Faster performance • Direct access to system memory

•IDE PORTS & CABLESIDE PORTS & CABLES

• IDE PORTS:IDE PORTS: Most motherboards come with an IDE interface. The interface is actually a host adapter, meaning that it provides a way to connect a complete device to the computer (host). The actual controller is on a circuit board attached to the hard drive. That's the reason it's called Integrated Drive Electronics in the first place!

• IDE CABLES:IDE CABLES: Also called Data Cables. They are the multiplied parallel wires ranked next each other. They are the transmission buses between the Hard Drives and the motherboard through the IDE Interface ( IDE Connectors ).

•PARALLEL PORTPARALLEL PORT

• Communication between a computer and printer.

• A parallel interface for connecting an external device such as a printer. Most personal computers have both a parallel port and at least one serial port.

• On PCs, the parallel port uses a 25-pin connector (type DB-25) and is used to connect printers, computers and other devices that need relatively high bandwidth.

•SERIAL PORTSERIAL PORT

• Considered to be one of the most basic external connections to a computer, the serial port has been an integral part of most computers for more than 20 years. Although many of the newer systems have done away with the serial port completely in favor of USB connections, most modems still use the serial port, as do some printers, PDAs and digital cameras. Few computers have more than two serial ports.

•USB PORTUSB PORT

• The Universal Serial Bus gives you a single, standardized, easy-to-use way to connect up to 127 devices to a computer. Each device can consume up to a maximum of 6 megabits per second (Mbps) of bandwidth, which is fast enough for the vast majority of peripheral devices that most people want to connect to their machines.

DISK DRIVESDISK DRIVES

• A device containing motors, electronics and other gadgetry for storing (writing) and retrieving (reading) data on a disk. A hard disk drive is one which is generally not removable from the machine. A floppy disk drive accepts removable disk cartridges.

Hard DiskHard Disk

• A mass storage device for digital data. One or more magnetic platters in a single casing, it can store data more precisely and access it more quickly than other forms of magnetic storage.

Floppy DiskFloppy Disk

• A thin, flexible plastic disk which has been coated with iron oxide, capable of storing computer data as a magnetic pattern. Almost all programs are sold on floppy disks, which are also used as a convenient way of swapping data between computers.

Compact DiskCompact Disk

• High density storage media based on a 4.75" reflective optical disc. Can hold up to 650,000,000 bytes of data, that is equivalent to 12,000 images or 200,000 pages of text.