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Introduction
One of the great strengths of the PC platform that has led to its overwhelming
success in the marketplace is its modularity. Most PCs are made up of many different
individual components, which can be mixed and matched in thousands of different
configurations. This lets you customize the PC you either buy or build to meet
your exact needs.
This section discusses some of the major components of a typical, modern PC.
Some PCs have some of these combined into one physical unit, but inside, somewhere,
you'll find most if not all of these pieces.
System Case
The box or outer shell that houses most of the computer, the system case is
usually one of the most overlooked parts of the PC. While it may seem inconsequential,
the case actually performs several important functions for your PC, including
protection for the computer circuits, cooling, and system organization. In addition,
the system case is normally purchased together with the system power supply,
and must also be matched with the size, shape and electrical requirements of
your motherboard. Therefore, it has an impact on your options with these important
components as well.
System Case
The system case, sometimes called the chassis or enclosure, is the metal and
plastic box that houses the main components of the computer. Most people don't
consider it a very important part of the computer (perhaps in the same way they
wouldn't consider their own skin a very important body organ). While the case
isn't as critical to the system as some other computer components (like the
processor or hard disk), it has several important roles to play in the functioning
of a properly-designed and well-built computer.
The case doesn't appear to perform any function at all, at first glance. However,
this isn't true; the case is in fact much more than just a box. The case has
a role to play in several important areas:
· Structure: The motherboard mounts into the case, and all the other
internal components mount into either the motherboard or the case itself. The
case must provide a solid structural framework for these components to ensure
that everything fits together and works well.
· Protection: The case protects the inside of your system from the outside
world, and vice-versa. Vice versa? Yes, although most people don't think about
that. With a good case, the inside of your computer is protected from physical
damage, foreign objects and electrical interference. Everything outside of your
computer is protected from noise created by the components inside the box, and
electrical interference as well. In particular, your system's power supply,
due to how it works, generates a good deal of radio-frequency (RF) interference,
which without a case could wreak havoc on other electronic devices nearby.
· Cooling: Components that run cool last longer and give much less trouble
to their owner. Cooling problems don't announce themselves; you won't get a
"System Cooling Error" on your screen, you'll get random-seeming lockups
and glitches with various parts of your system. You'll also have peripherals
and drives failing months or years before they do on your friend's computer,
and you'll never even dream that poor cooling is the cause. Making sure that
your system is cooled properly is one good way to save yourself time, trouble
and money.
Note: A spacious, well laid-out case is a critical part of proper system cooling.
Small cases require components to be packed close together, which reduces cooling
in two ways. First, air-flow through the case is reduced because it is blocked
by the components. Second, the parts are closer together so there is less space
for heat to radiate away from the devices that are generating it.
· Organization and Expandability: The case is key to a physical system
organization that makes sense. If you want to add a hard disk, CD-ROM, tape
backup or other internal device to your PC, the case is where it goes. If your
case is poorly designed or too small, your upgrade or expansion options will
be limited.
· Aesthetics: The system case is what people see when they look at your
computer. For some people this isn't important at all; for others it's essential
that their machine look good, or at least fit somewhat into their decor. In
an office environment, PCs that all look different can give a work center a
"hodge-podge" appearance that some consider unprofessional, for example.
· Status Display: The case contains lights that give the user information
about what is going on inside the box (not a lot, but some). Some of these are
built into the case and others are part of the devices that are mounted into
the case.
In terms of its actual operation, the case doesn't of course do a lot. It does
have switches and the above-mentioned status lights.
Power
Your computer is obviously an electronic device, and its many components of
course require power. Like the case, most people don't give much thought to
the power supplied to the system. The power supply in your PC can be compared
to the officials at a football game: if they are doing their jobs properly nobody
really notices them, but if they aren't, everybody knows it and lets them know
about it.
There are two aspects to power in the PC:
· External Power: External power refers to the power that is delivered
to the back of the system case. There are several considerations regarding this
power and how it is supplied that will determine if your internal power supply
is going to work the way it should.
· Power Supply: The power supply is the small box that sits inside your
case and takes the external power you supply to the computer. Its main job is
to transform this power into a form the rest of the computer can use.
The Power Supply
The internal power supply is responsible for converting your standard household
power into a form that your computer can use. The power supply is responsible
for powering every device in your computer; if it has a problem or is of low
quality you may experience many difficulties with your PC that you may not realize
are actually the fault of the electrical system. The power supply plays an important
role in the following areas of your system:
· Stability: A high quality power supply with sufficient capacity to
meet the demands of your computer will provide years of stable power for your
PC. A poor quality or overloaded power supply will cause all sorts of glitches
that are particularly insidious, because the problems occur in other, seemingly
unrelated, parts of the system. For example, power supplies can cause system
crashes, can make hard disks develop bad sectors, or cause software bugs to
appear, problems which can be very difficult to trace back to the power supply.
· Cooling: The power supply contains the main fan that controls the flow
of air through the PC case. This fan is obviously a major component in your
PC's cooling system.
· Energy Efficiency: Newer PC power supplies work with your computer's
components and software to reduce the amount of power they consume when at a
idle. This can lead to significant savings over older systems.
· Expandability: The capacity of your power supply is one factor that
will determine your ability to add new drives to your system, or upgrade to
a more powerful motherboard or processor. If you build a new system with a power
supply that barely meets your needs, you may have to replace it when you upgrade
down the road.
Motherboard and System Devices
The motherboard is the base of the modern computer system. If the processor
is the "brain" of the computer, then the motherboard is the "central
nervous system and circulatory system", plus much more, all rolled into
one. Here are the main parts of the motherboard and its related devices:
· Motherboard (Abit BD7-II Intel 845E Socket 478 ATX): The motherboard
is the main circuit board in the computer where everything comes together. This
is where you plug in your processor, memory, cache, video card and other cards.
It is also where you connect your peripherals.
· System Chipset and Controllers: The chipset and other motherboard circuitry
are the "smarts" of the motherboard. Their job is to direct traffic
and control the flow of information inside the computer. These circuits control
the processor's access to memory, the flow of data to and from peripheral devices
and communications lines, and much more. The chipset is a critical part of any
computer, because it plays a big role in determining what sorts of features
the computer can support. For example, which processors you can use, which types
of memory, how fast you can run the machine, and what kind of system buses your
PC can use, are all tied in to the type of chipset the motherboard uses.
· System Buses: The system buses are the electrical channels through
which various parts of the computer communicate. The physical part of these
buses, the part you see, is the set of slots in the back of the machine into
which you put your video card, sound card and other cards. It is over the system
buses that your video card gets information from the processor; the processor
saves data to your hard disk, etc. The architecture chosen for each of the system
buses have a great impact on the performance of your PC, as well as dictating
your choices for video cards and other devices.
· BIOS: The system BIOS (which stands for Basic Input/Output System and
is pronounced "bye-oss") is a computer program that is built into
the PC's hardware. It is the lowest-level program that runs on your computer.
Its job is to act as an intermediary between your system hardware (the chipset,
motherboard, processor and peripherals) and your system software (the operating
system). By doing this, the operating system doesn't have to be made different
for every machine, which is why DOS will load on any PC. The BIOS is what runs
when you turn on your computer, and what loads your operating system. The BIOS
also allows you to set or change many different parameters that control how
your computer will function. For example, you tell the BIOS what sort of hard
drives you have so it knows how to access them.
· Cache: The system cache is a small, high-speed memory area that is
placed between the processor and the system memory. The value of the cache is
that it is much faster than normal system memory. Each time the processor requests
a piece of data from the memory, the system first checks the cache to see if
the information is there. If it is, then the value is read from cache instead
of memory, and the processor can get back to work that much sooner. If it isn't,
then the data is read from memory and given to the processor, but it is also
placed into the cache in case the processor needs it again in the near future.
· System Resources: System resources are not actual physical devices;
they are nothing you can reach into the machine and touch. But they are very
important for two reasons. First, they dictate how your PC organizes its access
to various memory areas and devices. Second, they are one of the most common
areas where people have problems with the setup of their PCs (resource conflicts).
These are the four types of resources that various parts of your computer can
sometimes decide to fight over: o Interrupts (IRQs): A device requests time from the processor using these interrupt
requests. Under traditional designs, each device has a different IRQ number.
If two try to use the same one, a conflict can result. Newer technologies can
allow multiple devices to share an IRQ channel. o Direct Memory Access (DMA) Channels: Some devices have the ability to read
and write directly from the system memory, instead of asking the processor to
do it for them. Cutting the "middle man" out in this manner improves
the efficiency of the system. Each device that does this needs its own DMA channel.
o Input/Output (I/O) Addresses: Devices exchange information with the system
by putting data into certain specific memory addresses. For example, when we
pressed the letter "M" in the example mentioned above, the keypress
was stored in a certain memory address until it was time for the processor to
deal with it. Any time information goes into or out of the machine, to your
modem or hard drive or printer for example, it uses these I/O addresses. Again,
each device needs its own memory area. o Memory Addresses: Similar to I/O addresses, many devices use blocks of memory
as part of their normal functioning. For example, they may map hardware programs
(BIOS code) into memory, or use a memory area to hold temporary data they are
using.
Motherboard and System Devices
The motherboard is, in many ways, the most important component in your computer
(not the processor, even though the processor gets much more attention.) As
mentioned in the Overview, if the processor is the brain of the computer, then
the motherboard and its major components (the chipset, BIOS, cache, etc.) are
the major systems that this brain uses to control the rest of the computer.
Having a good understanding of how the motherboard and its contained subsystems
works is probably the most critical part of getting a good understanding of
how PCs work in general.
The motherboard plays an important role in the following important aspects of
your computer system (notice how many there are here):
· Organization: In one-way or another, everything is eventually connected
to the motherboard. The way that the motherboard is designed and laid out dictates
how the entire computer is going to be organized.
· Control: The motherboard contains the chipset and BIOS program, which
between them control most of the data flow within the computer.
· Communication: Almost all communication between the PC and its peripherals,
other PCs, and you, the user, goes through the motherboard.
· Processor Support: The motherboard dictates directly your choice of
processor for use in the system.
· Peripheral Support: The motherboard determines, in large part, what
types of peripherals you can use in your PC. For example, the type of video
card your system will use (ISA, VLB, PCI) is dependent on what system buses
your motherboard uses.
· Performance: The motherboard is a major determining factor in your
system's performance, for two main reasons. First and foremost, the motherboard
determines what types of processors, memory, system buses, and hard disk interface
speed your system can have, and these components dictate directly your system's
performance. Second, the quality of the motherboard circuitry and chipset themselves
have an impact on performance.
· Upgradability: The capabilities of your motherboard dictate to what
extent you will be able to upgrade your machine. For example, there are some
motherboards that will accept regular Pentiums of up to 133 MHz speed only,
while others will go to 200 MHz. Obviously, the second one will give you more
room to upgrade if you are starting with a 133 MHz Pentium.
The Processor(picture Intel Pentium 4 Willamette 1.8 GHz Socket 423 400 MHz)
One of the smallest parts of the computer but the one that gets most of the
attention, the processor is often thought of as the "brain" of the
computer. An extremely sophisticated piece of miniaturized electronics, the
processor (often called the CPU or Central Processing Unit) is at the bottom
of all tasks the PC performs. The processor reads instructions (commands) from
memory that tell it what it needs to do to accomplish the work that the user
wants, and then executes them.
The processor (really a short form for microprocessor) is the central component
of the PC. The processor performs all work that you do on your computer directly
or indirectly. The processor plays a significant role in the following important
aspects of your computer system:
· Performance: The processor is probably the most important single determinant
of system performance in the PC. While other components also play a key role
in determining performance, the processor's capabilities dictate the maximum
performance of a system. The other devices only allow the processor to reach
its full potential.
· Software Support: Newer, faster processors enable the use of the latest
software. In addition, new processors such as the Pentium with MMX Technology,
enable the use of specialized software (shortcuts) not usable on earlier machines.
· Reliability and Stability: The quality of the processor is one factor
that determines how reliably your system will run. While most processors are
very dependable, some are not. This also depends to some extent on the age of
the processor and how much energy it consumes.
· Energy Consumption and Cooling: Originally processors consumed relatively
little power compared to other system devices. Newer processors can consume
a great deal of power. Power consumption has an impact on everything from cooling
method selection to overall system reliability.
· Motherboard Support: The processor you decide to use in your system
will be a major determining factor in what sort of chipset you must use, and
therefore what motherboard you buy. The motherboard in turn dictates many facets
of your system's capabilities and performance.
· System Memory
The system memory holds all of the "active" information that the computer
is using. When you turn the computer on the memory is empty. Each program or
data file you load uses part of the system memory. When you close a program
the memory is freed up for other uses. Generally, the more memory your system
has, the more things you can do with it simultaneously. Increasing the amount
of memory in the system also improves performance in most cases.
The system memory is the place where the computer holds current programs and
data that are in use. The term "memory" is somewhat ambiguous; it
can refer to many different parts of the PC because there are so many different
kinds of memory that a PC uses. However, when used by itself, "memory"
usually refers to the main system memory or RAM, which holds the instructions
that the processor executes and the data that those instructions work with.
Your system memory is an important part of the main processing subsystem of
the PC, tied in with the processor, cache, motherboard and chipset.
Memory plays a significant role in the following important aspects of your computer
system:
· Performance: The amount and type of system memory you have is an important
contributing factor to overall performance. In many ways, it is more important
than the processor, because insufficient memory can cause a processor to work
at below its performance potential.
· Software Support: Newer programs require more memory than old ones.
More memory will give you access to programs that you cannot use with a lesser
amount.
· Reliability and Stability: Bad memory is a leading cause of mysterious
system problems. Ensuring you have high-quality memory will result in a PC that
runs smoothly and exhibits fewer problems. Also, even high-quality memory will
not work well if you use the wrong kind.
· Upgradability: There are many different types of memory available,
and some are more universal than others. Making a wise choice can allow you
to migrate your memory to a future system or continue to use it after you upgrade
your motherboard.
Read-Only Memory (ROM)
One major type of memory that is used in PCs is called read-only memory, or
ROM for short. ROM is a type of memory that normally can only be read, as opposed
to RAM, which can be both read and written. There are two main reasons that
read-only memory is used for certain functions within the PC:
· Performance: The values stored in ROM are always there, whether the
power is on or not. A ROM can be removed from the PC, stored for an indefinite
period of time, and then replaced, and the data it contains will still be there.
For this reason, it is called non-volatile storage. A hard disk is also non-volatile,
for the same reason, but regular RAM is not.
· Security: The fact that ROM cannot easily be modified provides a measure
of security against accidental or malicious changes to its contents. You are
not going to find viruses infecting true ROMs, it's just not possible. It's
technically possible with erasable EPROM's, though in practice never seen.
Read-only memory is most commonly used to store system-level programs that we
want to have available to the PC at all times. The most common example is the
system BIOS program, which is stored in a ROM called the system BIOS ROM. Having
this in a permanent ROM means it is available when the power is turned on so
that the PC can use it to boot up the system. Remember that when you first turn
on the PC the system memory is empty, so there has to be something for the PC
to use when it starts up.
While the whole point of a ROM is supposed to be that the contents cannot be
changed, there are times when being able to change the contents of a ROM can
be very useful. There are several ROM variants that can be changed under certain
circumstances; these can be thought of as "mostly read-only memory".
The following are the different types of ROMs with a description of their relative
modifiability:
· ROM: A regular ROM is constructed from hard-wired logic, encoded in
the silicon itself, much the way that a processor is. It is designed to perform
a specific function and cannot be changed. This is inflexible and so regular
ROMs are only used generally for programs that are static and mass-produced.
This product is analogous to a commercial software CD-ROM that you purchase
in a store.
· Programmable ROM (PROM): This is a type of ROM that can be programmed
using special equipment; it can be written to, but only once. This is useful
for companies that make their own ROMs from software they write, because when
they change their code they can create new PROMs without requiring expensive
equipment. This is similar to the way a CD-ROM recorder works by letting you
"burn" programs onto blanks once and then letting you read from them
many times. In fact, programming a PROM is also called burning, just like burning
a CD-R, and it is comparable in terms of its flexibility.
· Erasable Programmable ROM (EPROM): An EPROM is a ROM that can be erased
and reprogrammed. A little glass window is installed in the top of the ROM package,
through which you can actually see the chip that holds the memory. Ultraviolet
light of a specific frequency can be shined through this window for a specified
period of time, which will erase the EPROM and allow it to be reprogrammed again.
Obviously this is much more useful than a regular PROM, but it does require
the erasing light. This technology is analogous to a reusable CD-RW.
· Electrically Erasable Programmable ROM (EEPROM): The next level of
erasability is the EEPROM, which can be erased under software control. This
is the most flexible type of ROM, and is now commonly used for holding BIOS
programs. When you hear reference to a "flash BIOS" or doing a BIOS
upgrade by "flashing", this refers to reprogramming the BIOS EEPROM
with a special software program. Here we are blurring the line a bit between
what "read-only" really means, but remember that this rewriting is
done maybe once a year or so, compared to real read-write memory (RAM) where
rewriting is done often many times per second.
Note: One thing that sometimes confuses people is that since RAM is the "opposite"
of ROM (since RAM is read-write and ROM is read-only), and since RAM stands
for "random access memory", they think that ROM is not random access.
This is not true; any location can be read from ROM in any order, so it is random
access as well, just not write able. RAM gets its name because earlier read-write
memories were sequential, and did not allow random access.
Finally, one other characteristic of ROM, compared to RAM, is that it is much
slower, typically having double the access time of RAM or more. This is one
reason why the code in the BIOS ROM is often shadowed to improve performance.
Random Access Memory (RAM)
The kind of memory used for holding programs and data being executed is called
random access memory or RAM. RAM differs from read-only memory (ROM) in that
it can be both read and written. It is considered volatile storage because unlike
ROM, the contents of RAM are lost when the power is turned off. RAM is also
sometimes called read-write memory or RWM. This is actually a much more precise
name, so of course it is hardly ever used. ) It's a better name because calling
RAM "random access" implies to some people that ROM isn't random access,
which is not true. RAM is called "random access" because earlier read-write
memories were sequential and did not allow random access. Sometimes, old acronyms
persist even when they don't make much sense any more (e.g., the "AT"
in the old IBM AT stands for "advanced technology").
Obviously, RAM needs to be write able in order for it to do its job of holding
programs and data that you are working on. The volatility of RAM also means
that you risk losing what you are working on unless you save it frequently.
RAM is much faster than ROM is, due to the nature of how it stores information.
This is why RAM is often used to shadow the BIOS ROM to improve performance
when executing BIOS code. There are many different types of RAMs, including
static RAM (SRAM) and the many types of dynamic RAM (DRAM).
Static RAM (SRAM)
Static RAM is a type of RAM that holds its data without external refresh, for
as long as power is supplied to the circuit. This is contrasted to dynamic RAM
(DRAM), which must be refreshed many times per second in order to hold its data
contents. SRAMs are used for specific applications within the PC, where their
strengths outweigh their weaknesses compared to DRAM:
· Simplicity: SRAMs don't require external refresh circuitry or other
work in order for them to keep their data intact.
· Speed: SRAM is faster than DRAM.
In contrast, SRAMs have the following weaknesses, compared to DRAMs:
· Cost: SRAM is, byte for byte, several times more expensive than DRAM.
· Size: SRAMs take up much more space than DRAMs (which is part of why
the cost is higher).
These advantages and disadvantages taken together obviously show that performance-wise,
SRAM is superior to DRAM, and we would use it exclusively if only we could do
so economically. Unfortunately, 32 MB of SRAM would be prohibitively large and
costly, which is why DRAM is used for system memory. SRAMs are used instead
for level 1 cache and level 2 cache memory, for which it is perfectly suited;
cache memory needs to be very fast, and not very large.
SRAM is manufactured in a way rather similar to how processors are: highly-integrated
transistor patterns photo-etched into silicon. Each SRAM bit is comprised of
between four and six transistors, which is why SRAM takes up much more space
compared to DRAM, which uses only one (plus a capacitor). Because an SRAM chip
is comprised of thousands or millions of identical cells, it is much easier
to make than a CPU, which is a large die with a non-repetitive structure. This
is one reason why RAM chips cost much less than processors do.
Dynamic RAM (DRAM)
Dynamic RAM is a type of RAM that only holds its data if it is continuously
accessed by special logic called a refresh circuit. Many hundreds of times each
second, this circuitry reads the contents of each memory cell, whether the memory
cell is being used at that time by the computer or not. Due to the way in which
the cells are constructed, the reading action itself refreshes the contents
of the memory. If this is not done regularly, then the DRAM will lose its contents,
even if it continues to have power supplied to it. This refreshing action is
why the memory is called dynamic.
All PCs use DRAM for their main system memory, instead of SRAM, even though
DRAMs are slower than SRAMs and require the overhead of the refresh circuitry.
It may seem weird to want to make the computer's memory out of something that
can only hold a value for a fraction of a second. In fact, DRAMs are both more
complicated and slower than SRAMs.
The reason that DRAMs are used is simple: they are much cheaper and take up
much less space, typically 1/4 the silicon area of SRAMs or less. To build a
64 MB core memory from SRAMs would be very expensive. The overhead of the refresh
circuit is tolerated in order to allow the use of large amounts of inexpensive,
compact memory. The refresh circuitry itself is almost never a problem; many
years of using DRAM has caused the design of these circuits to be all but perfected.
DRAMs are smaller and less expensive than SRAMs because SRAMs are made from
four to six transistors (or more) per bit, DRAMs use only one, plus a capacitor.
The capacitor, when energized, holds an electrical charge if the bit contains
a "1" or no charge if it contains a "0". The transistor
is used to read the contents of the capacitor. The problem with capacitors is
that they only hold a charge for a short period of time, and then it fades away.
These capacitors are tiny, so their charges fade particularly quickly. This
is why the refresh circuitry is needed: to read the contents of every cell and
refresh them with a fresh "charge" before the contents fade away and
are lost. Refreshing is done by reading every "row" in the memory
chip one row at a time; the process of reading the contents of each capacitor
re-establishes the charge.
DRAM is manufactured using a similar process to how processors are: a silicon
substrate is etched with the patterns that make the transistors and capacitors
(and support structures) that comprise each bit. DRAM costs much less than a
processor because it is a series of simple, repeated structures, so there isn't
the complexity of making a single chip with several million individually-located
transistors.
There are many different kinds of specific DRAM technologies and speeds that
they are available in. These have evolved over many years of using DRAM for
system memory.
Video Cards(ATI Radeon 9800 PRO ATI Radeon 9800 Pro 256 MB DDR 256 biti TV-Out
-)
Your video card performs the function of displaying the screen you see on the
monitor. Inside the video card is a special kind of memory called video memory,
where information is stored that represents what you see on the screen. If you
look closely at the screen you can see that it is made up of many dots, or pixels.
Each pixel's color and brightness is stored in the video memory.
When the computer wants to display something, it calculates how it needs to
change the color and brightness of the different pixels, and changes the values
in the video memory. The video card then presents the new pixels to you on the
monitor. In modern computers, this calculating job is shared between the processor
and the video card itself. Having the video card do the calculation can often
be much faster, because the video card is specialized to do these types of calculations.
Also, while the video card is doing this work, the processor can go on to other
things.
Your system's video card is the component responsible for producing the visual
output from your computer. Virtually all programs produce visual output; the
video card is the piece of hardware that takes that output and tells the monitor
which of the dots on the screen to light up (and in what color) to allow you
to see it.
Like most parts of the PC, the video card had very humble beginnings, it was
only responsible for taking what the processor produced as output and displaying
it on the screen. Early on, this was simply text, and not even color at that.
Video cards today are much more like coprocessors; they have their own intelligence
and do a lot of processing that would otherwise have to be done by the system
processor. This is a necessity due to the enormous increase both in how much
data we send to our monitors today, and the sophisticated calculations that
must be done to determine what we see on the screen. This is particularly so
with the rise of graphical operating systems, and 3D computing.
The video card in your system plays a significant role in the following important
aspects of your computer system:
· Performance: The video card is one of the components that has an impact
on system performance. For some people (and some applications) the impact is
not that significant; for others, the video card's quality and efficiency can
impact on performance more than any other component in the PC! For example,
many games that depend on a high frame rate (how many times per second the screen
is updated with new information) for smooth animation, are impacted far more
by the choice of video card than even by the choice of system CPU.
· Software Support: Certain programs require support from the video card.
The software that normally depends on the video card the most includes games
and graphics programs. Some programs (for example 3D-enhanced games) will not
run at all on a video card that doesn't support them.
· Reliability and Stability: While not a major contributor to system
reliability, choosing the wrong video card can cause problematic system behavior.
In particular, some cards or types of cards are notorious for having unstable
drivers, which can cause a host of difficulties.
· Comfort and Ergonomics: The video card, along with the monitor, determine
the quality of the image you see when you use your PC. This has an important
impact on how comfortable the PC is to use. Poor quality video cards don't allow
for sufficiently high refresh rates, causing eyestrain and fatigue.
Monitors
In simple terms, the monitor, sometimes also called a CRT (Cathode Ray Tube)
after the main technology used in making them, is a specialized, high-resolution
screen, similar to a high-quality television. Many times per second, your video
card sends the contents of its video memory out to your monitor. The screen
is made up of a matrix of red, green and blue dots. The information your video
card sends controls which dots are lit up and how bright they are, which determines
the picture you see.
Your monitor is the component that displays the visual output from your computer
as generated by the video card. It is different from most of the other components
of the PC due to its passive nature; it isn't responsible for doing any real
computing, but rather for showing the results of computing. In this way, the
monitor is in many respects more similar to your printer than to anything else
in the PC, although of course most people don't think in these terms.
Monitors are important not because of their impact on performance, but rather
their impact on the usability of the PC. A poor quality monitor can hamper the
use of an otherwise very good PC, because a monitor that is hard to look at
can make the PC hard to use. Despite the fact that they don't have a direct
impact on performance, many people spend almost as much on their monitor when
buying a new PC as they do on the PC system itself.
One reason why this happens is that the monitor is one of the few parts of a
PC that actually holds its value. Performance items like CPUs get outdated and
lose their value rather quickly, but monitor technology evolves much more slowly.
Eventually, monitor costs have come down, but still much more slowly than most
other components. This is one big reason why quality is perhaps more important
in choosing a monitor than any other part of the system.
Your monitor plays a significant role in the following important aspects of
your computer system:
· Comfort and Ergonomics: Working with your video card, your monitor
determines the quality of the image you see when you use your PC. This has an
important impact on how comfortable the PC is to use. Poor quality monitors
lead directly to eyestrain and other problems, and can ruin the computing experience.
· Software and Video Mode Support: Use of advanced, high-resolution or
high-color-depth video modes requires support for these modes from the monitor.
A video card that can drive high resolutions in true color at high refresh rates
is useless without a monitor that can handle them as well.
· Upgradability: Since most monitors are interchangeable with each other
and can be used on any similar PC, they are naturals to carry over to a new
machine or to use after upgrading. Since they hold their value, a frequent upgrading
user with a good monitor can use it for many years and through many changes
of processors, memory, motherboards and other components that become dated quite
quickly.
Hard Disk Drives(Seagate Barracuda Serial ATA V 80 GB Serial-ATA 7200 rpm 8
MB cache)
Your hard disk drive is your computer's main "long term memory"--it
holds your operating system, programs and data files. Hard drives are the fastest
form of long-term storage your computer uses. They have currently increased
in size and speed to values unheard of just a few years ago. Hard disks are
(usually) permanent--they stay in one place inside your computer and cannot
be removed the way floppy disks or CD-ROMs can.
The hard disk drive in your system is the "data center" of the PC.
It is here that all of your programs and data are stored between the occasions
that you use the computer. Your hard disk (or disks) is the most important of
the various types of permanent storage used in PCs (the others being floppy
disks and other storage media such as CD-ROMs, tapes, removable drives, etc.)
The hard disk differs from the others primarily in three ways: size (usually
larger), speed (usually faster) and permanence (usually fixed in the PC and
not removable).
Hard disk drives are almost as amazing as microprocessors in terms of the technology
they use and how much progress they have made in terms of capacity, speed, and
price in the last 20 years. The first PC hard disks had a capacity of 10 megabytes
and a cost of over $100 per MB. Modern hard disks have capacities approaching
100 gigabytes and a cost of less than 1 cent per MB! This represents an improvement
of 1,000,000% in just under 20 years, or around 67% cumulative improvement per
year. At the same time, the speed of the hard disk and its interfaces has increased
dramatically as well.
Your hard disk plays a significant role in the following important aspects of
your computer system:
· Performance: The hard disk plays a very important role in overall system
performance, probably more than most people recognize (though that is changing
now as hard drives get more of the attention they deserve). The speed at which
the PC boots up and programs load is directly related to hard disk speed. The
hard disk's performance is also critical when multitasking is being used or
when processing large amounts of data such as graphics work, editing sound and
video, or working with databases.
· Storage Capacity: This is kind of obvious, but a bigger hard disk lets
you store more programs and data.
· Software Support: Newer software needs more space and faster hard disks
to load it efficiently. It's easy to remember when 1 GB was a lot of disk space;
heck, it's even easy to remember when 100 MB was a lot of disk space! Now a
PC with even 1 GB is considered by many to be "crippled", since it
can barely hold modern (inflated) operating system files and a complement of
standard business software.
· Reliability: One way to assess the importance of an item of hardware
is to consider how much grief is caused if it fails. By this standard, the hard
disk is the most important component by a long shot. As I often say, hardware
can be replaced, but data cannot. A good quality hard disk, combined with smart
maintenance and backup habits, can help ensure that the nightmare of data loss
doesn't become part of your life.
This chapter takes a very detailed look at hard disks and how they work. This
includes a full dissection of the internal components in the drive, a look at
how data is formatted and stored, a discussion of performance issues, and a
full analysis of the two main interfaces used to connect hard disks to the rest
of the PC. A discussion is also included about the many confusing issues regarding
hard disks and BIOS versions, and support for the newer and larger hard disks
currently on the market. Finally, a full description is given of logical hard
disk structures and the functioning of the FAT and NTFS file systems, by far
the most popular currently used by PCs.
Floppy Disk Drives
Floppy disks are your computer's smallest and slowest form of long-term storage.
Floppy disks provide a simple, convenient way to transfer information, install
new software, and back up small amounts of files. Floppy disks are not as important
a part of the computer as they were many years ago. This is largely because
the floppy disk still holds the same amount it did five years ago, while most
users' needs for storage, software installation and backup, have increased ten-fold
or more in that period of time. One great advantage floppy drives have is universality:
virtually 100% of PCs made in the last 10 years use a standard 1.44 MB floppy
drive.
Sometimes people refer to the hard disk as the "data center" of the
PC, and in fact it is, but there was a time when the floppy disk actually held
this honor. In fact, the first PCs didn't have hard disks; all of their data
storage was done on floppies. There was a time when floppy disk drives were
high technology and cost a lot of money. The invention of hard disks relegated
floppy disks to the secondary roles of data transfer and software installation.
The invention of the CD-ROM and the Internet, combined with the increasingly
large size of software files, is threatening even these secondary roles.
The floppy disk still persists, basically unchanged for over a decade, in large
part because of its universality; the 3.5 inch 1.44 MB floppy is present on
virtually every PC made in the last 10 years, which makes it still a useful
tool. The floppy disk's current role is in these areas:
· Data Transfer: The floppy disk is still the most universal means of
transferring files from one PC to another. With the use of compression utilities,
even moderate-sized files can be shoehorned onto a floppy disk, and anyone can
send anyone a disk and feel quite confident that the PC at the other end will
be able to read it. The PC 3.5" floppy is such a standard, in fact, that
many Apple and even UNIX machines can read them, making these disks useful for
cross-platform transfer.
· Small File Storage and Backup: The floppy disk is still used for storing
and backing up small amounts of data, probably more than you realize.
· Software Installation and Driver Updates: Many new pieces of hardware
still use floppies for distributing driver software and the like, and some software
still uses floppies (although this is becoming less common as software grows
massive and CD-ROM drives become more universal.)
While floppy drives still have a useful role in the modern PC, there is no denying
their reduced importance. Very little attention is paid to floppy "performance"
any more, and even choosing makes or models involves a small fraction of the
amount of care and attention required for selecting other components. In essence,
the floppy drive today is a commodity item.
CD-ROM Drives(Plextor PlexWriter SCSI Intern 40x12x40/)
CD-ROM stands for Compact Disk - Read Only Memory. As the name implies, CD-ROM
drives use compact disks, similar to the ones that hold music, to hold computer
information. And also as the name implies, they are a read-only medium. You
can read information from them but not write to them (except for some special
exceptions). CD-ROMs are currently the most popular way that computer companies
distribute applications and games, and are ideal for multimedia information
like videos, music and large graphics files.
In a few short years, the CD-ROM drive has gone from a pricey luxury to inexpensive
necessity on the modern PC. The CD-ROM has opened up new computing vistas that
were never possible before, due to its high capacity and broad applicability.
In many ways, the CD-ROM has replaced the floppy disk drive, but in many ways
it has allowed us to use our computers in ways that we never used them before.
In fact, the "multimedia revolution" was largely a result of the availability
of cheap CD-ROM drives.
As the name implies, CD-ROMs use compact disks, in fact, the same physical disk
format as the ones we use for music. Special formatting is used to allow these
disks to hold data. As CD-ROMs have come down in price they have become almost
as common in a new PC as the hard disk or floppy disk, and they are now the
method of choice for the distribution of software and data due to their combination
of high capacity and cheap and easy manufacturing. Recent advances in technology
have also improved their performance to levels approaching those of hard disks
in many respects.
CD-ROM drives play a significant role in the following essential aspects of
your computer system:
· Software Support: The number one reason why a PC today basically must
have a CD-ROM drive is the large number of software titles that are only available
on CD-ROM. At one time there were a few titles that came on CD-ROM, and they
generally came on floppy disks as well. Today, not having a CD-ROM means losing
out on a large segment of the PC software market. Also, some CD-ROMs require
a drive that meets certain minimum performance requirements.
· Performance: Since so much software uses the CD-ROM drive today, the
performance level of the drive is important. It usually isn't as important as
the performance of the hard drive or system components such as the processor
or system memory, but it is still important, depending on what you use the drive
for. Obviously, the more you use the CD-ROM, the more essential it is that it
perform well.
Keyboards
The keyboard is the main input device for most computers. It is used to input
textual information to the PC. Keyboards are pretty much standard affairs these
days, although they can vary greatly in quality and appearance, and some have
significant additional features.
Keyboards are one of those components that most PC users typically take for
granted. This is certainly understandable. For starters, keyboards have no impact
on the performance of the PC, which immediately diminishes their importance.
They are present on almost every PC ever sold, and usually just "come with"
the rest of the hardware. They perform a specific task and for a lot of people,
any keyboard will do the job. It’s not like the average PC buyer will
select a PC system on the basis of its keyboard! Pretty boring stuff, seemingly.
This can be deceiving, however. Despite the higher profile given to alternative
input devices in recent years, the lowly keyboard is still the primary input
mechanism for the PC. It is a one-dimensional input device, allowing you to
enter text and execute commands on your system. However, even in this day of
graphical user interfaces and Internet use, the keyboard has a very important
role to play.
The main reason for the keyboard’s importance is that it is one of the
most critical ergonomic components in the PC. The design and construction of
the keyboard affects the comfort and usability of the PC, especially if you
do a lot of typing. (And many people do more typing than they used to--the Internet
means more mouse-based graphical browsing, but also email, discussion forums
and other text-based activities.) Poor keyboard design and use habits can even
lead to health issues in some people: repetitive stress injuries.
Keyboards are probably the most standardized components in the PC, in terms
of operation and interface. You can switch most keyboards between PCs and still
have them work. This does not, however, mean that all keyboards are the same--far
from it. In fact, the interchangeability of most keyboards means you have a
wealth of options open to you. This freedom to easily change keyboards means
you can readily benefit from understanding the differences between different
types.
Mice
Until the invention of graphical operating systems, the keyboard was the only
way that most people input information into their PCs. Mice are used in graphical
environments to let users provide simple "point and click" instructions
to the computer. The main advantage of a mouse over the keyboard is simplicity.
There are also some operations that are much easier to perform with a mouse
than a keyboard (such as picking an item on a screen or choosing from a list
of options).