Computers in Libraries
Vol. 22, No. 7 Jul/Aug 2002 

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What's Under your PC's Hood: a Primer for Today's Machines
by Li Chen and Joyce White Mills

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 library.

When 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 library.

CPU: the Computer's Model and Horsepower
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 used.

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) is 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.
  • 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.
The Pentium 4 computer's memory module in today's market is either RDRAM or SDRAM.

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 drives.

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.
  • 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.
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.
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 ( Most of the current computers being sold today have the Windows XP operating system.

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 interface.

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 library.
Parts and Service Glossary
AGP Accelerated Graphics Port
Cache used by the computer to temporarily store previously accessed data
CPU Central Processing Unit
CRT monitor Cathode-Ray Tube monitor
DDR SDRAM Double Data Rate SDRAM
DRAM Dynamic Random-Access Memory
IDE Integrated Drive Electronics; a standard electronic interface used between the computer and its disk storage devices
IEEE 1394 port (FireWire) connector for peripherals that transfers data at much greater speeds than serial or parallel ports
LCD monitor Liquid Crystal Display monitor
PCI Peripheral Component Interconnect; an interconnection system between a microprocessor and attached devices
PS/2 port connector for keyboard and pointing device to the PC
RAM Random-Access Memory
RDRAM Rambus DRAM connectors
Serial and parallel ports standards and protocols that let you attach external peripherals to the PC
SDRAM Synchronous DRAM
Ultra DMA Ultra Direct Memory Access, also known as Ultra DMA/33 and Ultra ATA-33
USB Universal Serial Bus; a plug-and-play interface between a computer and add-on devices

Further Reading

Norton, Peter and Desmond, Michael. Peter
Norton's Complete Guide to PC Upgrades. Sams, Indianapolis, 1999.

Rosenthal, Morris. TheHand-Me-Down PC:
Upgrading and Repairing Personal Computers.McGraw-Hill, New York, 1998.

Mets, Card. "Whiz-Bang Boxes," PC Magazine (December 11, 2001): pp. 110­129.

Mets, Card. "Back to Business," PC Magazine (December 11, 2001): pp. 131­183.

Atermolen, Eric. "The Basics of Buying a Personal Computer System."

Li Chen is the systems librarian at Southern Polytechnic State University (SPSU) in Marietta, Georgia. Before that, she worked as an Oracle programmer and instructor for 3 years, at Towers Perrin in Atlanta as an information specialist, at the Canada Institute for Scientific and Technical Information (CISTI) as a systems librarian, and at Canada's Department of Foreign Affairs and International Trade as a librarian. She holds an M.L.I.S. from the University of Western Ontario in London, Ontario. Her e-mail address is

Joyce White Mills is director of the Lawrence V. Johnson Library at Southern Polytechnic State University (SPSU) in Marietta, Georgia. At SPSU, Mills has served as library science assistant professor, teaching School Media Center administration, general reference, and related courses; she has also organized the selection of several automated products. She holds a Ph.D. from Florida State University in Tallahassee, Florida. Her e-mail address is

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