Inside A
Computer.













3.5-inch
Drive Bay






There are
two types of 3.5-inch drive bays: internal and external. Internal
3.5-inch drive bays hold drives, like hard drives, that do not need to
be touched from outside of the computer. External 3.5-inch drive bays
hold drives, like floppy drives, that need their disks to be manually
inserted from outside of the computer. The picture above shows a Zip
drive on the left and a floppy drive on the right. Below is a picture of
a hard drive.







Hard
drives are sealed and contain disks that are not removable. For this
reason, they can be hidden inside of the computer, never to be seen.
This is why most hard drives are internal bay drives. The hard drive is
where your files and programs are stored for everyday use. They are
always there unless someone or something erases them. Normally,
computers will have one or two external, and two or three internal
3.5-inch drive bays.




5.25-inch
Drive Bay






5.25-inch
external drive bays can hold several different types of hardware. A CD
burner, like the one shown above, is just one example. CD-R disks can
store around 700MBs, (or 700,000,000 bytes), of information. A CD-R
drive can read and write information, but it cannot erase it. A CD-RW
drive can also read and write data, but it can also erase the data and
rewrite new data, which is useful if you save something and later wish
to remove it. CD-RW drives can use both CD-R disks and CD-RW disks. The
recording speed rating associated with CD-R drives varies up to 54x. It
varies up to 32x for CD-RW drives.




Motherboard
Battery






The
motherboard battery is used to preserve the computer's time and BIOS
settings while the computer is turned off. Some motherboards only need
the battery in case of a power outage. They draw the needed electricity
from the electrical outlet to power the clock. These motherboards save
their BIOS information to EEPROM. EEPROM stands for Electrically
Erasable Programmable Read Only Memory.





BIOS

Basic Input/Output
System







BIOS
stands for Basic Input/Output System. The photo above shows an example
of what a built in BIOS program looks like. BIOS programs vary from
computer to computer, but every computer has one. Without any disks or
even a hard drive, the BIOS program is always available, written
permanently on the BIOS chip. It is used to set up the computer's
hardware. Every time you boot your computer, you have the option of
entering "Setup." Setup is how you access the BIOS program. Only
experienced users should alter the BIOS settings. Improper BIOS settings
can cause major problems on a computer. The BIOS chip contains enough
information to operate the computer all by itself. When the computer is
first turned on (or booted), the BIOS program is in charge. After
booting and performing a few system checks, the BIOS program turns the
computer over to your operating system. Windows XP is an example of a
common operating system. Below is a picture of a BIOS chip. This chip is
where the BIOS program is stored.









The
Case






The
computer case is a very important part of the computer. It protects all
of the electronic components inside and provides adequate ventilation to
prevent overheating. The case also should be capable of allowing you to
expand your hardware if the need arises. Some cases only have 5 or 6
expansion bays. This may not be enough if you plan to add several
drives. There also should be plenty of expansion slots on the back for
adding AGP, ISA, PCI, PCIe, or other expansion cards. Cases are designed
for different types of motherboards. All motherboards won't work inside
of all cases. There are several different sizes of cases. The larger
cases have more expansion bays than the smaller cases have. The smallest
case is the "desktop" type that lies flat. The next size up is the
"mini tower," then the "mid tower," then the "full tower," and finally
the "server," which is the largest. The server case is primarily used
for server computers in businesses. The ATX mid tower case is the most
widely sold case for personal use.




Case
Fan






Case fans
are relatively inexpensive and are extremely important. Computer
components generate quite a bit of heat and must be kept as cool as
possible. The case fan is the primary source of cooling for most
computers. Although the importance of the fan is often overlooked, it is
the key to a long life for a computer. Most computer cases are designed
to allow a person to add one or more additional case fans.




Chipset

PCI/AGP/ISA/IDE
Controlers







Why is it
called a chipset? Because in the past there were always two or more of
these on a motherboard. Some motherboards now have only one chip that
performs all of the duties of the chipset, but others still use two or
more chips. Chipsets are like the motherboard's traffic cops. They
direct the flow of data from one point to another. Each chip in the
chipset has its own particular job. This is the 440BX chipset. One chip
links directly to the microprocessor. Above is a picture of the 440BX
chipset. Below is the "Intel 82443BX PCI/AGP Controller." It is hidden
under a heat sink that protects it from overheating.







The
82443BX Northbridge chip controls the data traffic between the
microprocessor and the rest of the motherboard. It also controls the
traffic to and from the AGP card. Both chips share in the task of
controlling the PCI and main memory data flow. In the diagram below you
can see the data flow paths mapped out for the chipset. The paths
managed by chip 1, (or the Northbridge chip), are shown in red. The
paths managed by chip 2, (or the Southbridge chip), are shown in blue.
The duties of the chips may vary slightly depending on the chipset. For
some chipsets, the Northbridge may control the CPU, video, and main
memory traffic, while the "Southbridge" chip may control the other
traffic.







The paths
between each component are referred to as "buses." Buses are simply the
paths, or wires, that connect one component to another. The chips in the
chipset are referred to as bridges, because they bridge the components
together and ensure that the data flow is directed to the proper place.
The better chipsets are those that can handle data the fastest and most
efficiently.









Expansion
Slots









Expansion
slot openings are located on the back of the computer. They look like
the ones shown in the picture above. They provide access to the AGP,
PCIe, PCI, and ISA expansion slots on the motherboard. Expansion cards,
like the one shown below, plug into these slots to add more devices to a
computer.









Memory







RAM is an
abbreviation for Random Access Memory. RAM is the computer's main
memory. The computer uses RAM constantly to temporarily store
information while it is working with it. The photo above shows what a
SDRAM DIMM memory module looks like. SDRAM stands for Synchronous
Dynamic Random Access Memory. SDRAM runs synchronously, (or at the same
pace), with the processor's front side bus. A bus is simply a connection
between items on the motherboard. The speed of the memory, or its data
transfer rate, is how fast the data can travel between the RAM and the
processor. The speed is measured in MHz, (or megahertz). The memory
module shown above is a DIMM module. DIMM stands for Dual In-line Memory
Module. The term DIMM has nothing to do with the speed or capacity of a
memory module. It simply refers to the way the module is designed. DIMM
modules consist of several DRAM chips. DIMM modules have separate
contact points on both sides of the module. Below is a picture of a
single DRAM memory chip.







Some
memory is capable of checking for errors. This memory is called ECC, (or
Error Correction Code), memory. If a computer has a lot of memory, it
can store a lot of temporary data and operate faster. People with good
memories also retain more information and do things faster, because they
don't waste a lot of time trying to remember things. Computers commonly
have 512MB to 1GB of memory.



The DDR
SDRAM memory module replaced the SDRAM memory module. DDR stands for
Double Data Rate. SDRAM runs at the same pace the system clock runs. DDR
SDRAM runs at double the pace the system clock runs. After DDR SDRAM
came DDR2 SDRAM. DDR2 SDRAM runs at four times the pace the system clock
runs. Below is a picture of a DDR2 SDRAM DIMM memory module.







Memory
Sockets






The
picture above is of 4 DIMM sockets. DIMM sockets are where the
computer's RAM, (or Random Access Memory), is installed. DIMM stands for
Dual Inline Memory Module. The reason it is called "Dual" is because
both sides of the memory module have completely separate connections
from the other side of the module. On the older SIMMs, (or Single Inline
Memory Modules), both sides were connected together at each contact
point on both sides of the module. Below is a partial picture of a
memory module's little gold contact points.









Microprocessor







The
microprocessor, (or CPU), is the brain of the computer. The picture
above shows a slot 1 processor with heatsinks and a fan, which prevent
it from overheating. Below is the processor without the heatsinks and
fan, being inserted into a slot 1 motherboard connection. Slot 1
processors have the microprocessor and level 2 cache memory mounted on a
circuit board, (or card), which is enclosed inside of a protective
shell.







The
enclosed slot 1 processor card contains the central processing unit, (or
CPU), with its level 1 cache memory. The central processing unit also
contains the control unit and the arithmetic/logic unit, both working
together as a team to process the computer's commands. The control unit
controls the flow of events inside the processor. It fetches
instructions from memory and decodes them into commands that the
computer can understand. The arithmetic/logic unit handles all of the
math calculations and logical comparisons. It takes the commands from
the control unit and executes them, storing the results back into
memory. These 4 steps, (fetch, decode, execute, and store), are what's
called the "machine cycle" of a computer. These 4 basic steps are how
the computer runs each and every program. The microprocessor's level 1
cache memory, is memory that is contained within the CPU itself. It
stores the most frequently used instructions and data. The CPU can
access the cache memory much faster than having to access the RAM, (or
Random Access Memory). Below is a picture of what's inside of a Pentium 3
processor. The control unit, arithmetic/logic unit, and level 1 cache
are contained within the center CPU chip. Level 2 cache memory is
visible on the right-hand side of the processor card.











Motherboard







The
motherboard is like a big city with many streets and highways that
connect all of the buildings together. Instead of streets and highways,
the motherboard uses tiny electrical paths to connect each component of
the computer together. These paths are called "buses." The more buses
that connect to a component, the faster it can operate. Larger buses are
able to operate faster than smaller buses. Buses work just like
highways. Wider highways and highways with more lanes are able to carry
more traffic than smaller highways and highways with less lanes. Many
cities have a freeway. A freeway is designed so that large amounts of
traffic can move quickly from one place to another. The "front side
bus," (or FSB), is the freeway of the motherboard. It is the most
important bus on the motherboard, because it connects the processor to
the main memory and the Northbridge chipset. Below is a diagram showing
the front side bus in red.







Like a
traffic cop, the chipset, (2 chips on this motherboard), manages and
directs the flow of data between each of the components. The BIOS is
where the computer's settings are stored and changed. In the first
picture of the slot 1 AOpen AX6B motherboard above, you can see most of
the connecting slots, ports, and connectors. Some are labeled to show
what they are. Motherboards are judged primarily by their chipsets and
their front side bus speed. The type of BIOS and the type and amount of
expansion slots are also other important things to consider.







Power
Cables






The power
cables supply electrical power from the power supply to the drives and
other devices. The power cables are red, yellow, and black. The yellow
wire furnishes 12 volts of power. The red wire furnishes 5 volts of
power. The two black wires are the ground wires for the yellow and red
wires. Some drives, like the 1.44MB floppy drive, use a smaller cable
and connector, but the wires still have the same voltage.





Power
Supply






The power
supply supplies the electrical power for a computer. It supplies power
to the motherboard, drives, and certain expansion cards. It normally has
at least one fan that helps cool the power supply and will assist in
the task of cooling the computer. Some power supplies have an additional
outlet on the back that can be used to provide power to the monitor.
Power supplies come in a variety of wattages. They range anywhere from
around 160 watts to about 700 watts. 350 to 400 watt power supplies are
probably the most common. A higher wattage power supply doesn't hurt
anything, but a lower wattage power supply can cause problems for people
with lots of devices connected to their computer





Video
Card






The AGP
expansion slot connects AGP video cards to a motherboard. Video
expansion cards are also known as graphic expansion cards. AGP stands
for Accelerated Graphics Port. AGP video cards are capable of a higher
data transfer rate than PCI video cards. Video cards, like the one shown
above, simply plug into an AGP slot and connect a monitor or other
video display device to a computer. The "DVI Out" connector shown in
picture above connects to a digital video display. DVI stands for
Digital Video Interface. Video cards with a TV output connection are
capable of displaying a computer's video on a television. Video cards
with a TV input connection are able of displaying a television's video
on a computer. The AGP card and the monitor are what determine the
quality of a computer's video display. The photo below shows what an AGP
slot looks like.





Sound
Card






The photo
above shows what a PCI slot looks like. PCI slots can handle 64 bits of
data at a time. ISA slots can only handle 32 bits of data at a time. PCI
stands for "Peripheral Component Interconnect." A 64-bit PCI slot has
64 connections to the motherboard. Each connection is capable of
handling 1 bit of data at a time. A 32-bit ISA slot has 32 connections
to the motherboard and can handle only 32 bits of data at a time. Below
is a picture of how a PCI card is installed.



Note:
Older technology ISA slots were 8-bit and 16-bit. The later EISA, (or
Extended ISA), slots are capable of 32-bit data transfer. Older PCI
technology was 32-bit. The newer PCI technology is 64-bit.







Below is a
picture of Creative's Sound Blaster Live Value PCI sound card. The
sound card is what processes a computer's sound data. When you hear
music coming from your computer's speakers, the sound card's digital
signal processor, (or DSP), is at work along with the digital-to-analog
converter, (or DAC), processing and converting digital sound data to
analog sound data. When you talk into your computer's microphone, the
sound card's DSP works along with the analog-to-digital converter, (or
ADC), to process and convert analog sound data to digital sound data.
Analog audio is continuous, like the sound waves from a person's voice.
Digital audio is broken into pieces that the computer can understand and
work with. Better sound cards have better sound. The Sound Blaster Live
Value card allows you to connect a sound input device (like a stereo), a
microphone, front speakers, rear speakers, and a joystick or MIDI
instrument (like a MIDI keyboard). The front and rear speakers can be
combined together to produce stereo surround sound. Just like the video
card, the sound card uses its own processor to process sound data.