Parts of system unit

Motherboard - The motherboard is the main circuit board of a microcomputer. It is also known as the mainboard or system board.

CPU - The CPU is the central electronic chip that determines the processing power of the computer.

Memory - Memory is the part of the computer that temporarily stores applications, documents, and stem operating information.

Bus - A bus is an electronic line that allows 1s and 0s to move from one place to another.

Expansion Slots - Expansions slots appear on the motherboard. They are sockets into which adapters are connected.

Ports and Connectors - A port is a connector located on the motherboard or on a separate adapter.

Bays - A bay is a space inside the computer case where a hard drive, floppy drive or CD-ROM drive sits

Power Supply - A power supply changes normal household electricity into electricity that a computer can use.

Sound Components - A sound card lets a computer play and record high quality sound.
Central Processing Unit (CPU)

Does all of the work for the computer

1. Does all of the mathematics, mainly addition
2. Does all the logical comparisons of values
3. Directs the flow of data in a computer
4. Controls the operation of the parts of the computer
   
   

Today, all CPUs are microprocessors

1. A microprocessor is a complete computer on a silicon chip
   • stores data and instructions waiting to be used
   • follows changeable instructions
   • does input, processing, and output
     
     
2. A microprocessor does all of the functions of a computer

CPUs have three basic parts

1. The Arithmetic Logic Unit (ALU)
2. #* does all of the mathematics in a computer
   • does all of the logic comparisons of values
   • some common logic comparison symbols
   • #** = equal to
     • < less than
     • > greater than
     • <= less than or equal to
     • >= greater than or equal to
     • <> not equal
       
       
   • directs the flow of information into the CPU and/or memory or storage
   • controls which instructions the CPU will do next
     
     
3. The Control Unit
   • Used to store data and instructions inside the processor
   • Size of the registers can affect the speed and performance of the processor
     
     
4. Registers

Speed of CPUs

1. The speed of CPUs is measured in hertzs.
2. #* A hertz is on cycle per second.
   • Need to measure time to determine cycles per second
   • #** All computers have a clock built into them for timing the cycles
     • The clock is usually located in a small metal box on the motherboard.
   • Today, many CPUs can complete over six (6) instructions per second.
     
     
   • Most computers have a CPU that can do more than 400 MHz.
   • #** MHz stands for megahertzs
     • A MHz is 1,000,000 cycles per second.
   • Computers will soon be at speeds of over a gigahertz, 1,000,000,000 Hertzs.
     
3. Speeds of modern CPUs

Memory

Primary memory can be used directly by the CPU

1. Consists of silicon chips, usually either VLS or VLSI technology is used to create the chips
   • Read Only Memory (ROM)
   • Random Access Memory (RAM)
2. Two forms of Primary Memory
3. Primary memory is also called primary storage

Read Only Memory (ROM)

1. Stores instructions that are used by the CPU
2. #* Tells the CPU how to be the kind of computer it is, for example a Windows, Macintosh, or Play Station computers.
   • Tells the CPU how to work with the different parts of the computer
   • ROM can also hold programs that are directly accessed by the CPU. One such program is the self-test when the computer is first turned on. The self-test tests to seem if all the parts on the main circuit board (mother board) are working correctly.
   • The instructions are built into the electronic circuits of the chips
   • These instructions in ROM are called firmware
   • To change the instructions in ROM you need to usually change the chips or do some other special process that is normally not available to an average user.
3. The instructions in ROM can not usually be changed
4. The instructions in ROM are nonvolatile. They stay in ROM even when the computer is turned off.
   • Random access means that any piece of information in ROM can be accessed at any given time without access other information first. It is a lot like the tracks on a music CD. You can access any track at any time and in any order.
   • The other kind of access is sequential access. You must access the information in the order that they are located. This is a lot like a music tape. You must play the songs in order, or you have to fast forward past songs to get to the one you want.
5. Access to information is random access.

Random Access Memory (RAM)

1. Store data and instructions that are used by the CPU to perform some task.
2. #* These instructions are usually loaded into RAM from a secondary storage device.
   • RAM is also used to store instructions that tell the CPU how to work with its parts. These instructions are usually called drivers.
3. The instructions in RAM are constantly changing, depending on the needs of the CPU.
   • When the computer is turned off the information in RAM disappears.
   • The information in RAM needs to be saved to secondary storage before the computer is turned off.
4. The instructions in RAM are volatile.
5. Access to information is random access.

Motherboard - The motherboard is the main circuit board of a microcomputer. It is also known as the mainboard or system board.

CPU - The CPU is the central electronic chip that determines the processing power of the computer.

Memory - Memory is the part of the computer that temporarily stores applications, documents, and stem operating information. 

 Bus - A bus is an electronic line that allows 1s and 0s to move from one place to another. 

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Figure 2-1. SGI Graphics Cluster Node

Figure 2-2 shows the interior of a node.

Figure 2-2. Node Interior

Motherboard (System Board)

The motherboard is mounted directly on the base of the chassis. Figure 2-3 points out motherboard features.

Figure 2-3. Node Motherboard Features

Table 2-1 summarizes the motherboard components. most of which are shown in Figure 2-3.

Table 2-1. Motherboard Components

Item	Description
BU1	Internal buzzer
BT1	Battery
CN1	CPU socket 1 thermal sensor connector
CN2	Above: PS/2 mouse port Below: PS/2 keyboard port
CN4	Above: Parallel port Left: Serial port 1 (COM2) Right: Serial port 2 (COM1)
CN5	BMC connector
CN6	Multi connector
CN7	LAN jack (RJ-45)
CN8	BMC connector
CN9	Wake on LAN connector
CN11	FDD connector
CN12	CPU socket 2 thermal sensor connector
CN13	12C connector
CN15	System fan connector
CN16	BP connector
CN17	IDE 1 connector
CN18	AGP slot
CN19	CD in connector
CN20	IDE 2 connector
CN21	Fax voice connector
CN22	SCSI channel B connector (68-pin) (Ultra 160/m)
CN25	SCSI channel A connector (68-pin) (Ultra 160/m)
CN26	System fan connector
CNX7	System fan connector
DIMM1-3	DIMM slots
UK1	Microphone in
JP1	CPU socket 2 fan connector
JP2	CPU socket 1 fan connector
JP3	SCSI channel A terminator 1-2 On (default) 2-3 Off
JP3X	SCSI channel B terminator 1-2 On (default) 2-3 Off
JP4	Onboard buzzer external speaker 1-2 Onboard buzzer (default) 2-3 External speaker
PCI1-5	PCI slots
PWR1	ATX power supply connector
PWR2	ATX power supply connector
U3	CPU socket 2
U15	Apollo Pro 133A chipset
U20	CPU socket 1
U30	Intel 82559 LAN chipset
U37	Apollo Pro 133A chipset
U46	Adaptec AIC-7899 chipset
WKUP1	Wake on Ring connector

For expandability, the motherboard includes one AGP (Accelerated Graphics Port) Pro bus, five PCI bus slots, and three DIMM sockets that allow memory installation to a maximum of 1 GB, using synchronous DRAM (SDRAM) DIMMs.

For connectivity, the motherboard supports a speaker-out/line-out, and microphone-in port. Other standard connectivity features are two NS16C550 UART serial ports, one enhanced parallel port with Enhanced Parallel Port/Extended Capabilities Port (EPP/ECP) support, a diskette drive interface, and two embedded hard disk interfaces.

Expansion Slots - Expansions slots appear on the motherboard. They are sockets into which adapters are connected.                                  

Ports and Connectors - A port is a connector located on the motherboard or on a separate adapter. 

  

Ports and Connectors - A port is a connector located on the motherboard or on a separate adapter. 

Bays - A bay is a space inside the computer case where a hard drive, floppy drive or CD-ROM drive sits 

Power Supply - A power supply changes normal household electricity into electricity that a computer can use.

Parts of system case

Parts of the System Case

A system case should normally come with a number of physical components. This will of course vary widely from system to system, depending to some extent on the form factor and overall design of the case. If you buy a case by itself for use in building your own machine, you should be able to check for all of these items. If you bought a pre-built system, many of these components were probably already put into the case when it was assembled, with left over materials kept by the company that made it.

Basic computer parts

If you use a desktop computer, you might already know that there isn't any single part called the "computer." A computer is really a system of many parts working together. The physical parts, which you can see and touch, are collectively called hardware. (Software, on the other hand, refers to the instructions, or programs, that tell the hardware what to do.)

The illustration below shows the most common hardware in a desktop computer system. Your system may look a little different, but it probably has most of these parts. A laptop computer has similar parts but combines them into a single notebook-sized package.

Desktop computer system

Let's take a look at each of these parts.

System unit

The system unit is the core of a computer system. Usually it's a rectangular box placed on or underneath your desk. Inside this box are many electronic components that process information. The most important of these components is the central processing unit (CPU), or microprocessor, which acts as the "brain" of your computer. Another component is random access memory (RAM), which temporarily stores information that the CPU uses while the computer is on. The information stored in RAM is erased when the computer is turned off.

Almost every other part of your computer connects to the system unit using cables. The cables plug into specific ports (openings), typically on the back of the system unit. Hardware that is not part of the system unit is sometimes called a peripheral device or device.

System unit

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Storage

Your computer has one or more disk drives—devices that store information on a metal or plastic disk. The disk preserves the information even when your computer is turned off.

Hard disk drive

Your computer's hard disk drive stores information on a hard disk, a rigid platter or stack of platters with a magnetic surface. Because hard disks can hold massive amounts of information, they usually serve as your computer's primary means of storage, holding almost all of your programs and files. The hard disk drive is normally located inside the system unit.

Hard disk drive

CD and DVD drives

Nearly all computers today come equipped with a CD or DVD drive, usually located on the front of the system unit. CD drives use lasers to read (retrieve) data from a CD, and many CD drives can also write (record) data onto CDs. If you have a recordable disk drive, you can store copies of your files on blank CDs. You can also use a CD drive to play music CDs on your computer.

CD

DVD drives can do everything that CD drives can, plus read DVDs. If you have a DVD drive, you can watch movies on your computer. Many DVD drives can record data onto blank DVDs.

Tip

If you have a recordable CD or DVD drive, periodically back up (copy) your important files to CDs or DVDs. That way, if your hard disk ever fails, you won't lose your data.

Floppy disk drive

Floppy disk drives store information on floppy disks, also called floppies or diskettes. Compared to CDs and DVDs, floppy disks can store only a small amount of data. They also retrieve information more slowly and are more prone to damage. For these reasons, floppy disk drives are less popular than they used to be, although some computers still include them.

Floppy disk

Why are floppy disks "floppy"? Even though the outside is made of hard plastic, that's just the sleeve. The disk inside is made of a thin, flexible vinyl material.

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Mouse

A mouse is a small device used to point to and select items on your computer screen. Although mice come in many shapes, the typical mouse does look a bit like an actual mouse. It's small, oblong, and connected to the system unit by a long wire that resembles a tail. Some newer mice are wireless.

Mouse

A mouse usually has two buttons: a primary button (usually the left button) and a secondary button. Many mice also have a wheel between the two buttons, which allows you to scroll smoothly through screens of information.

When you move the mouse with your hand, a pointer on your screen moves in the same direction. (The pointer's appearance might change depending on where it's positioned on your screen.) When you want to select an item, you point to the item and then click (press and release) the primary button. Pointing and clicking with your mouse is the main way to interact with your computer. For more information, see Using your mouse.

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Keyboard

A keyboard is used mainly for typing text into your computer. Like the keyboard on a typewriter, it has keys for letters and numbers, but it also has special keys:

• The function keys, found on the top row, perform different functions depending on where they are used.
• The numeric keypad, located on the right side of most keyboards, allows you to enter numbers quickly.
• The navigation keys, such as the arrow keys, allow you to move your position within a document or webpage.

Keyboard

You can also use your keyboard to perform many of the same tasks you can perform with a mouse. For more information, see Using your keyboard.

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Monitor

A monitor displays information in visual form, using text and graphics. The portion of the monitor that displays the information is called the screen. Like a television screen, a computer screen can show still or moving pictures.

There are two basic types of monitors: CRT (cathode ray tube) monitors and LCD (liquid crystal display) monitors. Both types produce sharp images, but LCD monitors have the advantage of being much thinner and lighter. CRT monitors, however, are generally more affordable.

LCD monitor (left); CRT monitor (right)

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Printer

A printer transfers data from a computer onto paper. You don't need a printer to use your computer, but having one allows you to print e‑mail, cards, invitations, announcements, and other materials. Many people also like being able to print their own photos at home.

The two main types of printers are inkjet printers and laser printers. Inkjet printers are the most popular printers for the home. They can print in black and white or in full color and can produce high-quality photographs when used with special paper. Laser printers are faster and generally better able to handle heavy use.

Inkjet printer (left); laser printer (right)

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Speakers

Speakers are used to play sound. They may be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.

Computer speakers

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Modem

To connect your computer to the Internet, you need a modem. A modem is a device that sends and receives computer information over a telephone line or high-speed cable. Modems are sometimes built into the system unit, but higher-speed modems are usually separate components.

Cable modem

What is computer?

A computer is a device that accepts information (in the form of digitalized data) and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed. Complex computers also include the means for storing data (including the program, which is also a form of data) for some necessary duration. A program may be invariable and built into the computer (and called logic circuitry as it is on microprocessors) or different programs may be provided to the computer (loaded into its storage and then started by an administrator or user). Today's computers have both kinds of programming.

Most histories of the modern computer begin with the Analytical Engine envisioned by Charles Babbage following the mathematical ideas of George Boole, the mathematician who first stated the principles of logic inherent in today's digital computer. Babbage's assistant and collaborator, Ada Lovelace, is said to have introduced the ideas of program loops and subroutines and is sometimes considered the first programmer. Apart from mechanical calculators, the first really useable computers began with the vacuum tube, accelerated with the invention of the transistor, which then became embedded in large numbers in integrated circuits, ultimately making possible the relatively low-cost personal computer.

Modern computers inherently follow the ideas of the stored program laid out by John von Neumann in 1945. Essentially, the program is read by the computer one instruction at a time, an operation is performed, and the computer then reads in the next instruction, and so on. Recently, computers and programs have been devised that allow multiple programs (and computers) to work on the same problem at the same time in parallel. With the advent of the Internet and higher bandwidth data transmission, programs and data that are part of the same overall project can be distributed over a network and embody the Sun Microsystems slogan: "The network is the computer."

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