|In this article, I will
discuss the PC's internal workings in hopes that a solid understanding
of the basics will help guide your search for a suitable computer for your
our library needed to buy computers, I found throughout the whole process
that buying a computer is just like buying an automobile. Most of us are
not automotive engineers, but as a part of the buying process when we do
decide to buy a car we make comparisons with other cars, always seeking
the perfect fit for who we are and what we want our purchase to do. If
you have a big family, you might want to buy a van. If you have a lot of
tools, you might want to buy a pickup. Of course, in this instance the
type of PC we wanted also depended on our library's budget. If your library
has the money, you can buy the top of the line for everyone involved. But
for one such as ours, with a limited budget, it was far more prudent to
do some major research before actually buying the computers.
I am Li Chen, systems librarian,
and Joyce Mills is the director at the Lawrence V. Johnson Library of Southern
Polytechnic State University in Marietta, Georgia. Ours is a small academic
library with six librarians and three assistants. The enrollment is just
under 4,000, and the collection consists of approximately 105,000 volumes,
60,000 nonbook items, and 2,000 periodical and serial titles. At the beginning
of 2001, the library was allocated a special fund for purchasing equipment;
in the meantime, our library software kept being upgraded. The old computers
that staff had could not efficiently support their daily work and some
older monitors were starting to malfunction.
To get started, I determined
the status of each workstation in the library. I did a computer inventory
and then checked the specification requirements of our library software.
I then analyzed what other uses the staff might need the computers for.
I categorized the jobs that needed higher-end systems, with more memory
and disk space, and other situations where that top system was not quite
so necessary. I also compared what kinds of computers the vendors on state
contract could offer. Throughout the process, I started to appreciate the
tremendous complexity and variation in the underlying PC technologies.
In this article, I will discuss the "under the hood" workings of hardware
and other aspects of computers in hopes that a solid understanding of the
basics will help guide you in your search for a suitable computer for your
CPU: the Computer's Model
There are two major kinds
of computers: the PC, known as an IBM compatible, and the Macintosh, made
by Apple, Inc. Here I will only discuss the PC since it is more widely
When buying a computer,
the first thing you need to examine is the Central Processing Unit's (CPU's)
type and speed. The CPU is the brain of the computer. It interprets all
the instructions that it receives from various devices and then executes
them. For example, it will tell the printer to print. The major types of
CPUs in the marketplace today are Intel Pentium (Pentium 4 is Intel's most
powerful desktop processor), Celeron (Intel Celeron is a low-cost processor),
and AMD (American Micro Devices) Athlon XP.
How fast the computer runs
depends on the speed of the chip and the size of the bus. The speed of
the clock and the size of the bus notably affect the speed of the PC. The
CPU clock speed is measured in millions of cycles per second, or megahertz
(MHz). A processor whose clock ticks 1 million times per second has a speed
of 1 MHz. One gigahertz (GHz) is equal to 1 billion hertz, or 1,000 MHz.
The higher the hertz rate, the faster the computer. The bus is the pathway
for moving information in and out of the CPU. The bigger the bus, the faster
it can move data between the CPU and other devices within the PC.
For example, a vendor may
list a computer as being an Intel Pentium 4 Processor at 1.7 GHz with a
400-MHz system bus. From this information, you know that this is a computer
with a Pentium 4 Processor, a speed of 1.7 GHz, and a bus size of 400 MHz.
Since our software's minimum requirement for a processor is 450 MHz, I
could only buy a computer that had a processor higher than this. Pentium
III processors are higher than 450 MHz, and most are measured in gigahertz.
Processor cache is another
descriptive term that computer vendors sometimes use. For example, Gateway
lists one of its computers as an Intel Celeron Processor 1,200 MHz (1.2
GHz) with a 256-KB cache. The cache is used by the computer to temporarily
store previously accessed data in order to greatly cut down on the amount
of time and effort needed to gather the data when they are needed again.
For example, the files you automatically request by looking at a Web page
are stored on your hard disk in a cache subdirectory. When you return to
a page you've recently looked at, the browser can get it from the cache
rather than from the original server, saving you time and the network the
burden of additional traffic. That is disk cache. The cache referred to
by PC vendors is CPU cache, but the concept is similar.
There are two levels of
cache memory. Level 1 cache (referred to as L1 or primary cache) is located
on the same chip as the processor. This is where the CPU will first look
when it wants to find some data. The Level 2 cache (referred to as L2 or
secondary cache) is a separate chip on the computer's motherboard. When
the CPU cannot find the data in its Level 1 cache, it will then look in
the Level 2 cache. If the CPU still cannot find the requested data in either
the Level 1 or Level 2 cache, it will then turn to the much slower system
memory (RAM), and then to other even slower storage devices, such as disks.
|"At refresh rates below
75, the human eye may notice the screen image flickering, and this can
cause eyestrain over extended viewing periods."
Different Types of Memory
In your computer shopping
you also need to examine information about the memory, or what is commonly
referred to as Random-Access Memory (RAM). The computer uses RAM as a temporary
storage area. Any data that you are using are temporarily stored in the
RAM, where they can be manipulated and used by the computer. When the computer
is turned off, all of the data in RAM are effectively wiped clean unless
saved onto hard drives, floppies, or writable CDs. Memory is measured by
megabytes (MB). (8 bits = 1 byte; 1,048,576 bytes = 1 megabyte; 1,073,741,824
bytes = 1 gigabyte.)
Though more is better, how
much is enough? Our library software requires a minimum of 128 MB RAM for
Windows 98 operating systems or 256 MB RAM for Windows 2000. Since we are
currently using Windows 2000, the computers that we buy need to have at
least 256 MB RAM.
There are four memory modules:
Dynamic random-access memory
(DRAM) was used in the 386 and 486 models.
Synchronous DRAM (SDRAM)
synchronized with the clock speed. This increases the number of instructions
that the processor can perform in a given time. SDRAM is still the cheapest
solution for most computer applications (word processing, e-mail, surfing
the Web, etc.).
Rambus DRAM (RDRAM)
is a type of memory module that was developed by The Rambus Corp. for use
with Intel Pentium 4 processors and that started showing up in new computers
at the end of 1999. It is better for multimedia streaming applications
such as audio and creation.
The Pentium 4 computer's memory
module in today's market is either RDRAM or SDRAM.
Double Data Rate SDRAM (DDR
SDRAM) is a fairly new type of memory that is being developed to compete
with RDRAM memory. DDR SDRAM is a type of SDRAM with speeds up to 200 MHz,
significantly higher than the current 133-MHz SDRAM standard, thus beneficial
for games, multimedia, and certain business applications.
Storage Devices: Getting
Some Extra 'Trunk Space'
You also need to look at
external storage, which consists of the hard drive, floppy disk, CD-ROM
or CD-RW, and DVD.
A hard drive, often called
"hard disk" or "hard disk drive," stores and provides relatively quick
access to large amounts of data, much more so than a floppy disk. The capacity
of a hard drive is measured by gigabytes (GB). Today's computers typically
come with a hard disk that contains several billion bytes (gigabytes) of
storage. You might come across IDE and Ultra DMA when you look at a hard
drive. Integrated Drive Electronics (IDE) is a standard electronic interface
used between the computer and the computer's disk storage devices. IDE
supports only a hard disk. Most computers sold today use an enhanced version
of IDE called Enhanced Integrated Drive Electronics (EIDE). This device
provides faster access to the hard drive and apart from the hard drive,
also supports additional drives including CD-ROM drives and tape devices.
Ultra Direct Memory Access
(Ultra DMA, or more accurately, Ultra DMA/33, also known as ATA-33) is
a protocol for transferring data between a hard disk drive through the
computer's bus to its RAM. Ultra DMA is the new technology, which transfers
data at a rate of 33.3 megabytes per second (MB/sec.), twice as fast as
the previous DMA interface. Most manufacturers today use Ultra ATA hard
Apart from the hard drive,
most PCs nowadays come with a floppy disk drive that uses a 3.5-inch high-density
floppy disk that can hold 1.44 megabytes of data. Almost every PC also
comes with a CD-ROM (compact disc read-only memory) drive, a CD-Read/Write
drive (commonly referred to as CD burner), or a DVD drive.
The data stored on the CD-ROM
disc cannot be erased or be added to. Two newer technologies have the ability
to write data, as well: CD-R (compact disc writable) allows users to write
information to the disc once, and CD-RW (compact disc rewritable) allows
users to write, erase, and rewrite data multiple times. The data transfer
rate for CD-ROM back to the PC is usually measured in kilobytes per second
(KB/sec.) and is referred to as an X-speed. One x (1x) transfers data at
150 KB/sec. A 10x drive translates to 1,500 KB/sec. The current standard
in CD-ROM drives for most computers is around 40x.
The DVD drive is the latest
in mass storage. DVD originally stood for Digital Video Disc or Digital
Versatile Disc. It is essentially a bigger, faster CD that can hold cinema-like
video, better in quality than CD audio and computer data. DVD drives can
also read CD-ROM, and will soon replace the CD.
Device Ports: Your PC's
Hitches and Racks
Another area where you
should look is to see how many ports the PC has.A port is generally a specific
place where other devices physically connect. There are five types of ports:
serial port, parallel port, Universal Serial Bus (USB), IEEE 1394 port,
and PS/2 port.
Serial ports provide
a standard connector and protocol to let you attach external peripherals,
such as modems, to your computer. They transmit the eight bits in the byte
one at a time. The advantage to this is that a serial port needs only one
wire to transmit the eight bits (while a parallel port needs eight). The
disadvantage is that it takes eight times longer to transmit the data than
it would take if there were eight wires. Serial ports lower cable costs
and make cables smaller. There are two serial port connectors: a compact
9-pin connector called DB-9 and a larger 25-pin connector called DB-25.
Old PCs used 25-pin connectors, but only about 9 pins were actually used,
so today most connectors are only 9-pin.
Parallel ports were
originally developed by IBM as a way to connect a printer to your PC. The
parallel port, able to move up to 8 MB/sec. of data, is fast enough for
most medium-strength data transfers, including printers, scanners, tape
backup drives, Zip drives, and others.
USB is a plug-and-play
interface between a computer and add-on devices (such as audio players,
keyboards, scanners, and printers). With it, a new device can be added
to your computer without having to add an adapter card or even having to
turn the computer off. USB takes over many of the duties served by serial
and parallel port buses. It provides a 12-MB/sec. data rate and connections
for up to 127 devices.
The IEEE 1394port, also
known as FireWire, is a plug-and-play standard that supports much higher
data rates (up to 400 MB/sec.) and up to 63 devices. It provides enhanced
connectivity between the PC and audio/video, storage peripherals, and other
portable devices. IEEE 1394 implementations are expected to replace and
consolidate today's serial and parallel interfaces.
Today, computers will have
one serial, one parallel, at least two USBs, and two PS/2 ports. The high-end
computers will also have an IEEE 1394 port.
The PS/2 port, a circular
connector, was developed by IBM to interface keyboards and pointing devices.
Nearly every PC will include PS/2 ports to connect a mouse and a keyboard.
|DVD is essentially a
bigger, faster CD that can hold cinema-like video, better in quality than
CD audio or computer data. These drives can also read CD-ROM, and will
soon replace the CD.
Multimedia: What You
Need for the Souped-Up PC
Multimedia, including graphics
cards and sound cards, is another area you should not neglect when you're
comparing PCs for purchase. A graphics card, also called "video adapter"
or "graphics accelerator," transforms video data on your computer. The
quality of the video you see on your monitor depends on both the video
card and the monitor. The more video card memory available, the faster
and better the image you will get on your monitor. To decide what video
card is best suited for your needs, you should first look at the video
card memory. These cards have their own memory to store graphical images
and free the computer's RAM for other tasks. The video memory is available
in three standard sizes: 16 MB, 32 MB, and 64 MB. In principle, the more
memory, the better.
You also need to look at
the graphics processor. The graphics card has been regarded as a specialized
coprocessor that is designed specifically to handle graphics data. Major
graphics chip vendors are nVidia, Creative Labs, and ATI. You also may
come across the term AGP when you look at a graphic card specification.
Accelerated Graphics Port (AGP) is an interface specification designed
to improve a system's graphics performance by increasing its bandwidth.
It helps the speed of the communication flow between the CPU and the graphics
controller. This enhancement allows texture maps of greater size, detail,
and realism, and even enables 3-D applications to run faster because of
the higher bandwidth. The data transfer rate for AGP is usually measured
in KB/sec. and referred to in X-speed. Most computer graphics cards today
are 4x AGP.
The sound card, also called
an audio adapter, is an expansion board that enables the computer to get,
process, and deliver sound. The market standard for sound card compatibility
in PCs is Creative Labs' Sound Blaster. Make sure to buy a computer with
a Sound Blaster-compatible sound card.
You also need to check how
many slots the computer has because you may wish to add more devices to
your PC at some point. Most computers have four PCI slots. PCI (Peripheral
Component Interconnect) is an interconnection system between a microprocessor
and attached devices in which expansion slots are spaced closely for high-speed
operation. These slots offer the advantage of easy plug-and-play installation.
Modem & Operating
System: the Lights on the Dashboard
Another key area is the
modem. This is a device that transmits data from your computer through
telephone lines. If you want to send e-mail, fax, or get on the Internet,
then you need a modem. There are two types of modems: external and internal.
While external modems are easy to install and allow you to transport the
drive between two or more computers, internal modems are a little cheaper.
Modems now come standard with most computers. They are available in different
speeds, which indicate the rate at which data is transmitted from one computer
to another (expressed in kilobits per second: Kbps, or K for short). A
faster modem decreases time spent waiting for Web pages to load. Today,
the standard speed is 56.6 Kbps. By specification, these modems can receive
data at speeds of 56,000 bits per second (56 Kbps) and send data at a rate
of 33.6 Kbps. The 56.6 modem is also referred to as V.90. This is the name
for the standard approved by International Telecommunication Union.
You may also come across
the term "network card." This is a chip that allows the computer to be
connected to a network. The chip, when connected to a cable, can allow
computers to share resources, information, and hardware. For example, library
computers that are connected to a network may be able to permit users to
simultaneously access the library cataloging database, send and receive
e-mail internally within the library, and share hardware devices such as
printers among several computers. Four primary network card manufacturers
are 3Com, Intel, Netgear, and Linksys.
You should also spend time
investigating operating systems to determine what is best suited to your
needs. An operating system (OS) is the large software program that manages
all the other programs in your computer when it is turned on. All major
computer platforms (hardware and software) require and sometimes include
an operating system. Windows 95/98/NT/Millennium (Me)/2000, OS/2, UNIX,
and Linux are all examples of operating systems.
Microsoft operating systems
break down into two major groups:
• Windows NT 4/2000/XP
Professional:These operating systems are for techies, such as programmers.
• Windows 95/98/Me/XP:
These operating systems are for the general public.
Windows 95 brought a number
of key features to the mainstream desktop PC. It is a 32-bit addressing,
multitasking operating system. Multitasking lets capable programs do more
than one thing at once, speeding performance when running multiple applications.
It also supports plug and play, which makes the installation of components
easy. Our library software does not support Windows 95 anymore, so when
we bought the new computers, we did not consider using it.
The major differences between
Windows 95 and Windows 98 are that Windows 98 integrates Microsoft's Internet
Explorer Web browser as a part of the operating system, and that it enhances
support for DVD and USB. Windows 2000 is reported to be more stable (less
apt to crash) than Windows 98/NT systems. Some of the new features include
safeguards that prevent important files and device drivers from being overwritten
during a software installation. It enables a company to encrypt data locally
or on the network, and to give users access to shared files in a consistent
way from any network computer. Since our library software needs Windows
98 or Windows 2000, as soon as our IT department buys a Windows 2000 license,
we will have that OS on our new PCs.
Windows XP is the latest
officially released version of the Windows desktop operating system for
the PC. It comes in a Professional and a Home Edition version and has a
faster start-up than previous Windows editions. As it is the most current
operating system available from Microsoft, information about it is quick
and easy to find (http://www.microsoft.com/windowsxp/default.asp).
Most of the current computers being sold today have the Windows XP operating
Choosing Your Windshield
Finally, we come to the
monitor. There are four major factors for buying a monitor: type, size,
dot pitch, and resolution. There are two basic types of computer monitors:
cathode-ray tube (CRT) monitors and liquid crystal display (LCD) monitors.
CRT is the technology used in television sets, which is a lower-cost, analog
signal, compatible with most VGA graphics cards. It has a wider viewing
angle. LCD technology, called "flat-panel display," is seen most often
in notebook computers, and is becoming more popular in desktop monitors.
It uses a digital or analog signal; graphics cards with digital ports are
required for digital models. Thin and lightweight, LCD monitors take up
less space and the images do not flicker. As LCD technology develops, it
will more closely map the viewing angle, resolution, and low price of CRT
technology, and so its popularity is expected to increase over time. Several
different sizes of monitors are available. Measured diagonally in inches,
there are 15-, 17-, 19-, and 21-inch monitors. Which size you choose depends
largely on your budget and overall use.
For CRT monitors, pay attention
to the following specifications: flicker-free resolution and dot pitch.
Resolution is a measurement of the number of pixels used to form an image
on the computer screen. For example, a screen resolution of 1024 x 768
has 1024 pixels in each horizontal row and 768 pixels in each vertical
column, for a total of 786,432 tiny pixels on the screen. The more pixels,
the sharper the image. However, it does take a monitor longer to display
the extra pixels in a higher-resolution screen. So at higher resolutions,
the "refresh rate" of the screen image slows down. Maybe the monitor can
redraw an 800 x 600 screen image 120 times every second, but at a higher
resolution like 1280 x 1024 it can only redraw the image 60 times every
second. At refresh rates below 75, the human eye may notice the screen
image flickering, and this can cause eyestrain over extended viewing periods.
You may want to use a resolution that is high enough to give you sharp
detail, but low enough that the monitor is able to redraw the screen quickly,
so that no flickering is noticeable. The "flicker-free" resolution is the
highest resolution with a refresh rate of 75 or above, which is fast enough
to avoid tiring out the eyes. For LCD monitors, you can use the highest
resolution available for the monitor without worrying about eyestrain due
to screen flicker.
Dot pitch is the diagonal
distance between two dots (phosphors) of the same color. The closer together
these dots are, the sharper the picture can be and the higher the screen
resolution can be. Aperture grill pitch, or "slot pitch," is a similar
measurement used by monitors that arrange phosphors into stripes instead
of dots. A .25-mm slot pitch is roughly equal to a .27-mm dot pitch. For
today's monitors, a .25-mm or smaller aperture grill pitch is recommended,
unless the monitor is a 14- or 15-inch model.
The interface is simply
the type of port that the monitor uses to connect to your computer. Unlike
CRT monitors, almost all of which use a standard analog VGA port, LCD monitors
can use either a VGA or a digital port. An analog interface slightly degrades
the picture, but uses the same convenient cable as a regular CRT monitor,
while a digital interface produces a superior picture with no analog degradation.
Some newer monitors accept both digital and analog inputs, giving you the
option of using a standard VGA connection or a special digital LCD graphics-card
Conclusion: Drivers Wanted.
I have discussed several
of the most important components of a computer in this article. You might
wonder, what kind of PCs did I end up buying? Just like purchasing a car,
buying our PCs required us to make difficult choices. Based on the budget,
product availability, and staff and patron needs, the PCs in our library
fell into three categories. The top-of-the-lines are the PCs with AMD Duran
950-MHz processors (equivalent to Pentium III), 256MB of memory, and 20-GB
hard drives. We bought these PCs for library staff. We decided to use the
Windows 2000 operating system for its stability and reliability, and to
satisfy the library software requirement standardized by the state systems.
By choosing Windows 2000 to run the library's client software, we needed
at minimum a Pentium III 450-MHz CPU with 256 MB RAM and 256 MB of the
available harddrive's space.
For the workstations that
are dedicated only to our university's library catalog and Galileo (Georgia's
Web-based virtual library, which provides access to resources including
licensed databases, selected Internet sites, and participating libraries'
catalogs), I installed computers with AMD Duran 800-MHz processors (equivalent
to Pentium III), 128 MB of memory, and 20-GB hard drives. I did not upgrade
those workstations that staff and students use only to do CD-ROM searching
and word processing. They are Pentium II with 64 MB of memory. I did not
buy modems, but NICs (Network Interface Cards) instead, because we access
the Internet via our university's network systems. When choosing between
19-inch CRT monitors, which are less expensive and have bigger screens,
but that occupy more space, and 15-inch flat-panel monitors, which are
just the opposite in those three aspects, we decided to go with the 19-inch
CRTs with .26-mm resolution, 75-Hz refresh rate, and flat screens, since
our budget considerations outweighed our space constraints.
As we all know, things are
changing rapidly in the computer industry. When I started planning to buy
computers in January 2001, Windows XP was not yet released and Pentium
4 was not yet regarded as a mature product. Nowadays, new PCs with Pentium
4 processors and Windows XP are fairly common. In this article, I covered
only the computer hardware and software issues that I dealt with in my
library at the time we did the upgrading. There are a lot of books and
Web sites that further discuss computer components and software. You may
wish to visit some of the sites and read some of the books listed below
to better inform yourself before you actually purchase computers for your
Parts and Service
by the computer to temporarily store previously accessed data
Data Rate SDRAM
Drive Electronics; a standard electronic interface used between the computer
and its disk storage devices
1394 port (FireWire)
for peripherals that transfers data at much greater speeds than serial
or parallel ports
Crystal Display monitor
Component Interconnect; an interconnection system between a microprocessor
and attached devices
for keyboard and pointing device to the PC
and parallel ports
and protocols that let you attach external peripherals to the PC
Direct Memory Access, also known as Ultra DMA/33 and Ultra ATA-33
Serial Bus; a plug-and-play interface between a computer and add-on devices
Norton, Peter and Desmond,
Norton's Complete Guide
to PC Upgrades. Sams, Indianapolis, 1999.
Rosenthal, Morris. TheHand-Me-Down
Upgrading and Repairing
Personal Computers.McGraw-Hill, New York, 1998.
Mets, Card. "Whiz-Bang Boxes,"
Magazine (December 11, 2001): pp. 110129.
Mets, Card. "Back to Business,"
Magazine (December 11, 2001): pp. 131183.
Atermolen, Eric. "The Basics
of Buying a Personal Computer System."