HARDWARE

personal computer is made up of multiple physical components of computer hardware, upon which can be installed an operating system and a multitude of software to perform the operator's desired functions.

Contents Typical PC hardware Motherboard Power supply Video display controller Removable media devices Internal storage Sound card Other peripherals

Typical PC hardware

Hardware of Personal Computer.
1. Monitor
2. Motherboard
3. CPU
4. RAM Memory
5. Expansion card
6. Power supply
7. CD-ROM Drive
8. Hard Disk
9. Keyboard
10. Mouse

INSIDE A CUSTOM COMPUTER.

Though a PC comes in many different form factors, a typical personal computer consists of a case or chassis in a tower shape (desktop) and the following parts:

Motherboard

The motherboard is the main component inside the case. It is a large rectangular board with integrated circuitry that connects the rest of the parts of the computer including the CPU, the RAM, the disk drives (CD, DVD, hard disk, or any others) as well as any peripherals connected via the ports or the expansion slots.

Components directly attached to the motherboard include:

• The central processing unit (CPU) performs most of the calculations which enable a computer to function, and is sometimes referred to as the "brain" of the computer. It is usually cooled by a heat sink and fan.
• The chipset mediates communication between the CPU and the other components of the system, including main memory.
• RAM Stores all running processes (applications) and the current running OS. RAM Stands for Random Access Memory
• The BIOS includes boot firmware and power management. The Basic Input Output System tasks are handled by operating system drivers.
• Internal Buses connect the CPU to various internal components and to expansion cards for graphics and sound.
• Current
• The northbridge memory controller, for RAM and PCI Express
• PCI Express, for expansion cards such as graphics and physics processors, and high-end network interfaces
• PCI, for other expansion cards
• SATA, for disk drives
• Obsolete
• ATA (superseded by SATA)
• AGP (superseded by PCI Express)
• VLB VESA Local Bus (superseded by AGP)
• ISA (expansion card slot format obsolete in PCs, but still used in industrial computers)
• External Bus Controllers support ports for external peripherals. These ports may be controlled directly by the southbridge I/O controller or based on expansion cards attached to the motherboard through the PCI bus.
• USB
• FireWire
• eSATA
• SCSI

Power supply

Includes power cords, switch, and cooling fan. Supplies power at appropriate voltages to the motherboard and internal disk drives. It also converts alternating current to direct current and provides different voltages to different parts of the computer.

A power supply unit (PSU) is the component that supplies power to the other components in a computer. More specifically, a power supply unit is typically designed to convert general-purpose alternating current (AC) electric power from the mains (220-240V in most of the world) to usable low-voltage DC power for the internal components of the computer. Some power supplies have a switch to change between 230 V and 115 V. Other models have automatic sensors that switch input voltage automatically, or are able to accept any voltage between those limits.

The most common computer power supplies are built to conform with the ATX form factor. This enables different power supplies to be interchangeable with different components inside the computer. ATX power supplies also are designed to turn on and off using a signal from the motherboard, and provide support for modern functions such as the standby mode available in many computers. The most recent specification of the ATX standard PSU as of mid-2008 is version 2.31.

Note that some manufacturers, most notably Compaq and Dell, have produced power supplies using the same connectors as ATX but with different voltages on different pins; mismatching such PSUs and motherboards can result in damage to either or both.

Contents Appearance 2.1 Connectors AT vs. ATX Laptops Servers Wiring diagrams Modular power supplies Troubleshooting

Power rating

Computer power supplies are rated based on their maximum output power. Typical power ranges are from 300 W to 500 W (lower than 300 W for Small form factor systems) and are intended for ordinary home computers, the use of which is limited to Internet-surfing and burning and playing DVDs, Power supplies used by gamers and enthusiasts mostly range from 450 W to 1400 W. Typical gaming PCs feature power supplies in the range of 500-800 W, with higher-end PCs demanding 800-1400 W supplies. The highest-end units are up to 2 kW strong and are intended mainly for servers and, to a lesser degree, extreme performance computers with multiple processors, several hard disks and multiple graphics cards (ATI CrossFire or NVIDIA SLI). The power rating of a PC power supply is not officially certified and is self-claimed by each manufacturer. A common way to reach the power figure for PC PSUs is by adding the power available on each rail, which will not give a true power figure. Therefore it is possible to overload a PSU on one rail without having to use the maximum rated power.

Sometimes manufacturers inflate their power ratings, in order to gain an advantage in the market. This can be done due to a lack of clear standards regarding power supply labelling and testing. Some of the main ways employed are…

• Advertising the peak power, rather than the continuous power;
• Determining the continuous output power capability at unrealistically low temperatures (at room temperature as opposed to 40°C, a more likely temperature inside a PC case);
• Advertising total power as a measure of capacity, when modern systems are almost totally reliant on the current available from the 12 volt line(s).

This may mean that if:

• PSU A has a peak rating of 550 watts at 25°C, with 25 amps (300 W) on the 12 volt line, and
• PSU B has a continuous rating of 450 watts at 40°C, with 33 amps (400 W) on the 12 volt line,

and those ratings are accurate, then PSU B would have to be considered a vastly superior unit, despite its lower overall power rating. PSU A may only be capable of delivering a fraction of its rated power under real world conditions.

This tendency has led in turn to greatly overspecified power supply recommendations, and a shortage of high-quality power supplies with reasonable capacities. Very few computers require more than 300–350 watts maximum.^[2] Higher end computers such as servers and gaming machines with multiple high power GPUs are among the few exceptions.

Appearance

Most computer power supplies are a square metal box, and have a large bundle of wires emerging from one end. Opposite the wire bundle is the back face of the power supply, with an air vent and C14 IEC connector to supply AC power. There may optionally be a power switch and/or a voltage selector switch. A label on one side of the box lists technical information about the power supply, including safety certifications maximum output power. Common certification marks for safety are the UL mark, GS mark, TÜV, NEMKO, SEMKO, DEMKO, FIMKO, CCC, CSA, VDE, GOST R and BSMI. Common certificate marks for EMI/RFI are the CE mark, FCC and C-tick. The CE mark is required for power supplies sold in Europe and India.

A RoHS or 80 PLUS can also sometimes be seen.

Dimensions of an ATX power supply are 150 mm width, 86 mm height, and typically 140 mm depth, although the depth can vary from brand to brand.

Connectors

Typically, power supplies have the following connectors:

• PC Main power connector (usually called P1): Is the connector that goes to the motherboard to provide it with power. The connector has 20 or 24 pins. One of the pins belongs to the PS-ON wire (it is usually green). This connector is the largest of all the connectors. In older AT power supplies, this connector was split in two: P8 and P9. A power supply with a 24-pin connector can be used on a motherboard with a 20-pin connector. In cases where the motherboard has a 24-pin connector, some power supplies come with two connectors (one with 20-pin and other with 4-pin) which can be used together to form the 24-pin connector.
• ATX12V 4-pin power connector (also called the P4 power connector). A second connector that goes to the motherboard (in addition to the main 24-pin connector) to supply dedicated power for the processor. For high-end motherboards and processors, more power is required, therefore EPS12V has an 8 pin connector.
• 4-pin Peripheral power connectors (usually called Molex for its manufacturer): These are the other, smaller connectors that go to the various disk drives of the computer. Most of them have four wires: two black, one red, and one yellow. Unlike the standard mains electrical wire color-coding, each black wire is a ground, the red wire is +5 V, and the yellow wire is +12 V. In some cases these are also used to provide additional power to PCI cards such as FireWire 800 cards.
• 4-pin Berg power connectors (usually called Mini-connector or "mini-Molex"): This is one of the smallest connectors that supplies the floppy drive with power. In some cases, it can be used as an auxiliary connector for AGP video cards. Its cable configuration is similar to the Peripheral connector.
• Auxiliary power connectors: There are several types of auxiliary connectors designed to provide additional power if it is needed.
• Serial ATA power connectors: a 15-pin connector for components which use SATA power plugs. This connector supplies power at three different voltages: +3.3, +5, and +12 volts.
• 6-pin Most modern computer power supplies include 6-pin connectors which are generally used for PCI Express graphics cards, but a newly introduced 8-pin connector should be seen on the latest model power supplies. Each PCI Express 6-pin connector can output a maximum of 75 W.
• 6+2 pin For the purpose of backwards compatibility, some connectors designed for use with PCI Express graphics cards feature this kind of pin configuration. It allows either a 6-pin card or an 8-pin card to be connected by using two separate connection modules wired into the same sheath: one with 6 pins and another with 2 pins.
• A C14 IEC connector with an appropriate C13 cord is used to attach the power supply to the local power grid.

AT vs. ATX

A typical installation of an ATX form factor computer power supply.

There are two basic differences between AT and ATX power supplies: The connectors that provide power to the motherboard, and the soft switch. On older AT power supplies, the Power-on switch wire from the front of the computer is connected directly to the power supply.

On newer ATX power supplies, the power switch on the front of the computer goes to the motherboard over a connector labeled something like; PS ON, Power SW, SW Power, etc. This allows other hardware and/or software to turn the system on and off.

The motherboard controls the power supply through pin #14 of the 20 pin connector or #16 of the 24 pin connector on the motherboard. This pin carries 5V when the power supply is in standby. It can be grounded to turn the power supply on without having to turn on the rest of the components. This is useful for testing or to use the computer ATX power supply for other purposes.

AT stands for Advanced Technology when ATX means Advanced Technology eXtended.

Laptops

Most portable computers have power supplies that provide 25 to 100 watts. In portable computers (such as laptops) there is usually an external power supply (sometimes referred to as a "power brick" due to its similarity, in size, shape and weight, to a real brick) which converts AC power to one DC voltage (most commonly 19 V), and further DC-DC conversion occurs within the laptop to supply the various DC voltages required by the other components of the portable

Servers

Some web servers use a single-voltage 12 volt power supply. All other voltages are generated by voltage regulator modules on the motherboard.^[3]

Wiring diagrams

AT power connector (Used on older AT style mainboards)
Color	Pin	Signal
	P8.1	Power Good
	P8.2	+5 V
	P8.3	+12 V
	P8.4	−12 V
	P8.5	Ground
	P8.6	Ground
	P9.1	Ground
	P9.2	Ground
	P9.3	−5 V
	P9.4	+5 V
	P9.5	+5 V
	P9.6	+5 V

24-pin ATX12V 2.x power supply connector (20-pin omits the last 4: 11, 12, 23 and 24) Color Signal Pin Pin Signal Color Orange +3.3 V 1 13 +3.3 V Orange +3.3 V sense Brown Orange +3.3 V 2 14 −12 V Blue Black Ground 3 15 Ground Black Red +5 V 4 16 Power on Green Black Ground 5 17 Ground Black Red +5 V 6 18 Ground Black Black Ground 7 19 Ground Black Grey Power good 8 20 −5 V (obsolete) White Purple +5 V standby 9 21 +5 V Red Yellow +12 V 10 22 +5 V Red Yellow +12 V 11 23 +5 V Red Orange +3.3 V 12 24 Ground Black

The four shaded pins (8, 9, 13, 16) are data signals, not power.

Modular power supplies

A modular power supply is a relatively new approach to cabling, allowing users to omit unused cables. Whereas a conventional design has numerous cables permanently connected to the power supply, a modular power supply provides connectors at the power supply end, allowing unused cables to be detached from the power supply, producing less clutter, a neater appearance and less interference with airflow. It also makes it possible to supply a wider variety of cables, providing different lengths of Serial ATA power connectors instead of Molex connectors.

While modular cabling can help reduce case clutter, they have often been criticized for creating electrical resistance. Some third party websites that do power supply testing have confirmed that the quality of the connector, the age of the connector, the number of times it was inserted/removed, and various other variables such as dust can all raise resistance. However, the amount of this resistance in a good connector is small compared to the resistance generated by the length of the wire itself.^[10]

Troubleshooting

A power supply is tasked with providing electricity to every component in a computer, so a faulty or under performing unit will often cause a wide range of symptoms, including, but not limited to:

• Failure to power on.
• General instability.
• Rebooting, either randomly or when the computer is stressed.
• Hardware failure, due to sudden power spikes/dips or long term electronic noise.
• Inability to boot up even though motherboard light is lit. At power on, there is no activity at all except for fans and disks starting to spin.

Power supplies can also fail when the electrolytic capacitors inside dry up and/or become defective. This can be a common reason of power supply failure.

Power supply testers are available. These typically have a single socket for each common type of power supply connector, and use several LEDs to indicate if the power supply is working. They cannot usually indicate problems resulting from the power supply being overloaded by connected hardware.

Most desktop computer power supplies are equipped with a cooling fan, which helps to keep internal components cool and operating more efficiently. Abnormal fan noise is generally caused by dust, a lack of internal lubrication or a failing motor. Dust may be removed by carefully blowing air through the supply with an air pump or gas duster.

The capacitors inside can retain electric charge hours or days after the system has been off and powered down. The charge is strong enough to cause severe damage when touched. Because of this, blowing out the dust without opening the PSU is the best option to quiet a noisy fan.

Video display controller

Produces the output for the computer monitor. This will either be built into the motherboard or attached in its own separate slot (PCI, PCI-E, PCI-E 2.0, or AGP), in the form of a graphics card.

Most video cards support the most basic requirements, and video card manufacturing companies are doing a good job of keeping up with the requirements the games need. However the games are still evolving faster than the video because of manufacturing companies.

REMOVABLE MEDIA DEVICES

Main article: Computer storage

• CD (compact disc) - the most common type of removable media, suitable for music and data.
• CD-ROM Drive - a device used for reading data from a CD.
• CD Writer - a device used for both reading and writing data to and from a CD.
• DVD (digital versatile disc) - a popular type of removable media that is the same dimensions as a CD but stores up to 12 times as much information. It is the most common way of transferring digital video, and is popular for data storage.
• DVD-ROM Drive - a device used for reading data from a DVD.
• DVD Writer - a device used for both reading and writing data to and from a DVD.
• DVD-RAM Drive - a device used for rapid writing and reading of data from a special type of DVD.
• Blu-ray Disc - a high-density optical disc format for data and high-definition video. Can store 70 times as much information as a CD.
• BD-ROM Drive - a device used for reading data from a Blu-ray disc.
• BD Writer - a device used for both reading and writing data to and from a Blu-ray disc.
• HD DVD - a discontinued competitor to the Blu-ray format.
• Floppy disk - an outdated storage device consisting of a thin disk of a flexible magnetic storage medium. Used today mainly for loading RAID drivers.
• Iomega Zip drive - an outdated medium-capacity removable disk storage system, first introduced by Iomega in 1994.
• USB flash drive - a flash memory data storage device integrated with a USB interface, typically small, lightweight, removable, and rewritable. Capacities vary, from hundreds of megabytes (in the same ballpark as CDs) to tens of gigabytes (surpassing, at great expense, Blu-ray discs).
• Tape drive - a device that reads and writes data on a magnetic tape, used for long term storage and backups.

INTERNAL STORAGE

Hardware that keeps data inside the computer for later use and remains persistent even when the computer has no power.

• Hard disk - for medium-term storage of data.
• Solid-state drive - a device similar to hard disk, but containing no moving parts and stores data in a digital format.
• RAID array controller - a device to manage several internal or external hard disks and optionally some peripherals in order to achieve performance or reliability improvement in what is called a RAID array.

SOUND CARD

Enables the computer to output sound to audio devices, as well as accept input from a microphone. Most modern computers have sound cards built-in to the motherboard, though it is common for a user to install a separate sound card as an upgrade. Most sound cards, either built-in or added, have surround sound capabilities.

OTHER PERIPHERALS

In addition, hardware devices can include external components of a computer system. The following are either standard or very common.

Wheel Mouse

Includes various input and output devices, usually external to the computer system.

INPUT

• Text input devices
• Keyboard - a device to input text and characters by depressing buttons (referred to as keys), similar to a typewriter. The most common English-language key layout is the QWERTY layout.
• Pointing devices
• Mouse - a pointing device that detects two dimensional motion relative to its supporting surface.
• Optical Mouse - a newer technology that uses lasers, or more commonly LEDs to track the surface under the mouse to determine motion of the mouse, to be translated into mouse movements on the screen.
• Trackball - a pointing device consisting of an exposed protruding ball housed in a socket that detects rotation about two axes.

• Gaming devices
• Joystick - a general control device that consists of a handheld stick that pivots around one end, to detect angles in two or three dimensions.
• Gamepad - a general handheld game controller that relies on the digits (especially thumbs) to provide input.
• Game controller - a specific type of controller specialized for certain gaming purposes.
• Image, Video input devices
• Image scanner - a device that provides input by analyzing images, printed text, handwriting, or an object.
• Webcam - a low resolution video camera used to provide visual input that can be easily transferred over the internet.
• Audio input devices
• Microphone - an acoustic sensor that provides input by converting sound into electrical signals.