How Laptops Work Maybe you have been thinking about buying a computer, and it has occurred to you that you might want to buy a laptop version. After all, today's laptops have just as much computing power as desktops, without taking up as much space. You can take a laptop on the road with you to do your computing or make presentations. Perhaps you prefer comfortably working on your couch in front of the TV instead of sitting at a desk. Maybe a laptop is for you.we will examine how these portable computers do the same work as larger computers, but in much smaller packages.  A Brief History
Alan Kay of the Xerox Palo Alto Research Center originated the idea of a portable computer in the 1970s. Kay envisioned a notebook-sized, portable computer called the Dynabook that everyone could own, and that could handle all of the user's informational needs. Kay also envisioned the Dynabook with wireless network capabilities. Arguably, the first laptop computer was designed in 1979 by William Moggridge of Grid Systems Corp. It had 340 kilobytes of bubble memory, a die-cast magnesium case and a folding electroluminescent graphics display screen (click here for a picture). In 1983, Gavilan Computer produced a laptop computer with the following features:
- 64 kilobytes (expandable to 128 kilobytes) of random access memory (RAM)
- Gavilan operating system (also ran MS-DOS)
- 8088 microprocessor
- touchpad mouse
- portable printer
- weighed 9 lb (4 kg) alone or 14 lb (6.4 kg) with printer
The Gavilan computer had a floppy drive that was not compatible with other computers, and it primarily used its own operating system. The company failed.
In 1984, Apple Computer introduced its Apple IIc model (click here for picture). The Apple IIc was a notebook-sized computer, but not a true laptop. It had a 65C02 microprocessor,128 kilobytes of memory, an internal 5.25-inch floppy drive, two serial ports, a mouse port, modem card, external power supply, and a folding handle. The computer itself weighed about 10 to 12 lb (about 5 kg), but the monitor was heavier. The Apple IIc had a 9-inch monochrome monitor or an optional LCD panel. The combination computer/ LCD panel made it a genuinely portable computer, although you would have to set it up once you reached your destination. The Apple IIc was aimed at the home and educational markets, and was highly successful for about five years.
Later, in 1986, IBM introduced its IBM PC Convertible. (click here for a picture.) Unlike the Apple IIc, the PC Convertible was a true laptop computer. Like the Gavilan computer, the PC Convertible used an 8088 microprocessor, but it had 256 kilobytes of memory, two 3.5-inch (8.9-cm) floppy drives, an LCD, parallel and serial printer ports and a space for an internal modem. It came with its own applications software (basic word processing, appointment calendar, telephone/address book, calculator), weighed 12 lbs (5.4 kg) and sold for ,500. The PC Convertible was a success, and ushered in the laptop era. A bit later, Toshiba was successful with an IBM laptop clone.
Since these early models, many manufacturers have introduced and improved laptop computers over the years. Today's laptops are much more sophisticated, lighter and closer to Kay's original vision.
Anatomy of a Laptop Computer
To illustrate the parts of a laptop computer, we will show you the inside of a Toshiba Satellite Pro laptop.
The major parts of the Toshiba Satellite Pro laptop computer.
|
Like all computers, laptops have a central brain called a microprocessor, which performs all of the operations of the computer.
The microprocessor:
- Has a set of internal instructions stored in memory, and can access memory for its own use while working.
- Can receive instructions or data from you through a keyboard in combination with another device (mouse, touchpad, trackball, trackstick).
- Can receive and store data through several data storage devices (hard drive, floppy drive, Zip drive, CD/DVD drive).
- Can display data to you on computer monitors (cathode ray monitors, LCD displays).
- Can send data to printers, modems, networks and wireless networks through various input/output ports.
- Is powered by AC power and/or batteries.
Schematic diagram showing the various parts of a laptop computer. |
How Laptops Are Like Desktops
For the most part, laptops have the same major parts as desktops:
- microprocessor
- operating system
- solid-state memory
- disk drives
- input/output ports
- sound cards and speakers
Microprocessors
Like standard desktops, laptops are powered by microprocessors. The microprocessor is the brain of the laptop and coordinates all of the computer's functions according to programmed instructions (that is, the operating system software). The DX-4 processor shown in the photo below is no longer used, but it is typical of modern laptop microprocessors in that it is customized for laptop use. A typical laptop processor has features that reduce power consumption and heat. For example, laptop processors often run at a lower voltage and often have multiple sleep or slow-down modes that significantly increase battery life. Typical laptop microprocessors include Motorola's PowerPC family (used in Apple Macintosh computers), Intel's Pentium and Celeron families (used in PCs) and AMD's K5 and K6 families (used in PCs).
Close-up of the Toshiba's Intel 486 DX4 microprocessor. This microprocessor is no longer used in laptop computers |
Operating Systems
The operating system is the set of pre-programmed instructions that tell the microprocessor what to do. Operating systems on laptops include Windows 98/2000/NT (Microsoft) and Mac OS, depending upon the type of computer (PC vs. Mac), and Linux (Linux is not an option for most consumers, but some third-party developers are writing applications for this operating system on laptops).
Memory
Laptops have memory , both RAM and ROM, just like desktops. The laptop's ROM chip contains the BIOS just as it does in a desktop computer.RAM stores the application software and data files while the computer is on. RAM differs on a laptop in that it uses a different form factor -- that is, the size and shape of the modules that carry the RAM. Manufacturers have to build laptops to be portable (smaller) and to withstand more jostling (durable) than a desktop would ever get, so the memory modules have to be different. While some laptops use a standard Small Outline Dual Inline Memory Module (SODIMM), others use the manufacturer's proprietary memory modules. Most laptops should have at least 64 MB of RAM to have sufficient memory to run operating systems and applications software. Also, some laptops allow you to upgrade the memory of your computer and come equipped with convenient access panels to plug in additional memory chips.
Close-up of Toshiba's memory chips. |
Disk Drives
Like desktops, laptops have various disk drive storage devices. All laptops have an internal hard disk drive, usually 6 to 20 gigabytes (GB). The hard disk drive stores operating systems, application programs and data files. Although the hard disk drive works the same in a laptop as it does in a desktop, laptops generally have less disk space than desktops and you will have fewer choices for hard disk drives in laptops. The smaller hard disk space is one of the chief limitations of laptops.
Close-up of Toshiba's CD-ROM drive. |
In addition to hard drives, most laptops have some type of removable disk storage system, such as floppy disks, Zip disks, compact discs (CD) and DVDs. There are three options for disk drives in laptops:
- Some laptops have more than one bay built into the case for disk drives (such as floppy drive and CD-ROM drive).
- Some laptops have one bay that you can swap or interchange various drives. You just pull one drive out and put another in:
- "cold-swappable" drive - You must turn the computer off, change drives, then reboot the computer.
- "hot-swappable" drive - You can change the drives without turning the computer off. This feature saves you the time involved in restarting the computer.
- Some laptops have no internal drives. All drives are external and connected to the computer by cables. This feature allows the laptop to be very small and thin.
Input/Output Ports
Computers need to talk to other devices (such as printers, modems and networks). Computers send and receive information through various input/output ports, which can include serial ports, parallel ports and Universal Serial Bus (USB) ports.
The back panel of the Toshiba Satellite Pro laptop computer, showing the various input/output ports.
|
In addition to ports, some laptops have expansion slots for PCMCIA standard adapter cards (Type I and Type II) or "PC" cards. These cards can be used to upgrade your laptop by adding memory, a modem, a network connection or a peripheral device (for example, a CD-ROM drive).
The Toshiba Satellite Pro has a PC card for modem/Ethernet connections.
Sound Cards and Speakers
Like desktops, most laptops are equipped with sound cards and speakers so they can play music from CDs. However, the quality of the speakers built into most laptops does not match that of speakers for desktops, because space is a major limitation in a laptop case. The Toshiba laptop that we dissected has a sound card and jacks so you could hook up a microphone or headphones; it also has a small speaker for sound.
How Laptops Differ from Desktops
Laptops differ from desktops in the following features:
- power supply
- displays
- input devices
- docking connections
Power Supply
Like desktops, laptops can be plugged into the wall to receive AC power from the electric power grid through an AC adapter. But what makes the laptop unique is that it is portable; so, laptops are also powered by batteries. All laptops use some type of rechargeable battery (lithium, nickel-cadmium, nickel-metal hydride).
The Toshiba Satellite Pro's rechargeable battery. |
The battery life varies depending on the type of rechargeable battery (lithium batteries tend to hold their charge longer) and how you use your computer (frequent use of disk drives consumes a lot of battery power). In addition to the main battery, laptops have other batteries to run clocks and backup CMOS RAM.
The Toshiba Satellite Pro's backup batteries. |
Many laptop computer models have power management software to extend the battery life, or conserve battery power when the battery is low. You may notice that as your battery gets low, your laptop runs slower. This effect is typically the result of internal power management software, and indicates that you should plug in the computer's AC adapter, or quit and re-charge your battery.
Displays
All laptops have some type of LCD display screen. Laptop LCD displays can be:
- 12 to 15 inches
- black-and-white (16 grayscale) or color (65,536 colors)
- passive or active matrix - active matrix displays have sharper images and are easier to read
- reflective or backlit - backlit screens are good for low-level room lighting conditions
Front view of the Toshiba's LCD panel. |
Back view of the Toshiba's LCD panel, showing the fluorescent tube that provides the light and the screen that diffuses the light evenly over the surface.
|
Modern laptop computers have 800 x 600 pixel resolution, which makes for a clear screen; anything less than this resolution should be avoided.
Input Device
For a desktop computer, you typically use a keyboard and mouse to enter data. However, because using a mouse takes up room, other devices are built into laptops to take its place. Laptops come with one of three input devices:
- trackball - rotating the ball allows you to move the cursor on the LCD screen
- trackpoint - pushing your finger over the point allows you to move the cursor
- touchpad - moving your finger across the pad allows you to move the cursor
All of these devices have buttons that act like the right and left buttons on a mouse. Also, most laptops have a port that allows you to hook up a mouse to your laptop if you wish.
Close-up of a touchpad from another laptop computer. |
Docking Connections
Some people find that it is difficult or uncomfortable to use a laptop at their desk. The screen may be too small to see adequately. The keyboard may be slightly smaller than a standard keyboard. The touch pad may not be as comfortable to use as a mouse. Perhaps they want to have access to more than one type of disk drive. To make the laptop more convenient for desktop use, the docking station was invented. The docking station has several peripheral devices (full-size computer monitor, full-size keyboard, mouse, disk drives, printer) connected to it. You just plug your laptop into the station to use it as a desktop computer; in other words, you make one connection to your laptop instead of many. Most laptops have a docking connection.
Future Trends
Like any other computer, future laptops will have faster microprocessors with more memory. The storage devices may change from removable disks (floppy, Zip, CD, DVD) to solid state memory, which could make them even lighter and thinner.
In the future, laptops may eventually be replaced by wearable computers.
What They Can Do
A laptop is a full-blown, genuine computer that can do anything a desktop computer can do. For example, you can do programming, word processing, spreadsheets, databases, accounting and multimedia presentations.
The portability of laptops allows you to do many things that you cannot do with a desktop. For example, you can write your sales proposal, article or business presentation while travelling on a plane, or commuting on the bus or train or subway. We will discuss some examples of laptop uses in the following fields:
- education
- entertainment
- law enforcement
- amateur astronomy
- navigation
- business
Education
Students and educators have found that laptops answer a lot of their needs. In fact, some colleges and universities that require incoming freshmen to have computers recommend laptops. Teachers have found a variety of uses for laptops, too.
Lecture Presentations
In college, where lectures to large classes are commonplace, many professors can use their laptops, along with other audiovisual equipment, to project slides or lecture notes. And as technology creeps further into public elementary, middle and high schools, there is a growing trend toward teachers using laptops in the classroom for lectures.
Notetaking
Students can use laptop computers to take notes during lectures; this is more common in college than in lower schools. However, many special education students do use laptops for notetaking, or to run specialized software, such as hearing interpreters. As another example, if a student is injured and cannot use his/her writing arm, the school system may issue a laptop for notetaking or for downloading notes supplied by the teacher.
Laboratories
In both colleges and lower schools, science students can use laptops for gathering data from laboratory experiments. Laptops can also be taken into the field to gather data. For example, laptops can be hooked up to probes, such as pH electrodes or temperature probes, and taken to a salt marsh, stream or lake. Students can then measure pH and temperature and use the data to study the environment. In addition to laptops, scientific calculators and PDAs can also be equipped for taking these types of measurements.
Other uses
Laptops are becoming quite commonly used for business and for pleasure.
Entertainment
Because most laptops either have standard or optional internal CD-ROM or DVD drives, you can play music CDs or movie DVDs on your laptop. Imagine sitting on a long flight or train commute during which you can type your presentation for work, and listen to your own music CD. Or perhaps you're on a plane and you don't like the in-flight movie; if your laptop has a DVD drive, you can just pop in your own movie and enjoy!
Law Enforcement
Many police cars are now equipped with laptop computers. Police officers can use laptops to type incident reports immediately at the scene, rather than take notes and type the reports later. This time saving feature allows them more time to patrol. Furthermore, police can also use laptops with wireless connections to central police headquarters to check such things as criminal records, vehicle registrations and outstanding warrants, which saves time and can assist in making arrests.
Amateur Astronomy
Because laptop computers are so portable, amateur astronomers can take them easily to observing sites. Computers can be used to drive telescopes to various celestial objects. Furthermore, if the telescope is equipped with a CCD camera, the laptop computer can be used to acquire process and display the image from the CCD.
Navigation
When sailing and boating, it is essential to know precisely where you are on the water. On small boats, space is a premium; they cannot have chartrooms or large chart tables. So, you can use a laptop computer, equipped with appropriate software and a global positioning system (GPS) device, for precise navigation.
Business
Some may say that the business field has benefited the most from the laptop computer. Salespeople can use the laptop to make presentations to customers, access company data over the Internet and process orders while on the road. At trade shows and conventions, it is easy to setup a laptop for a multimedia presentation of your company's products and services.
Features
When you shop for a laptop, you should take a look at the features of the models you are considering to figure out what you need. We will look at features that have to do with the performance and the convenience of the computer.
Performance
Features that affect the performance of the computer include:
- microprocessor
- operating system
- RAM
- disk drives
- display
- battery
- input/output ports
- fax/modem
- sound cards and speakers
Microprocessors
Like standard desktops, laptops are powered by microprocessors. The microprocessor is the brain of the laptop and coordinates all of the computer's functions according to programmed instructions (i.e. the operating system software). For Apple Macintosh users, the choice of microprocessor is limited. Powerbooks and iBooks are equipped with special processors designed for use with Apple Laptops only. For PC users, there is a wider variety. You can choose from Intel's Pentium and Celeron families or AMD's K5 and K6 families. Powerful Pentium microprocessors tend to be found in high-end laptops, whereas Celeron and AMD chips tend to be found in lower-end models. The choice between these chips depends upon your needs for speed versus cost.
Operating Systems
The operating system is the set of pre-programmed instructions that tells the microprocessor what to do.
You may also want to consider that the latest operating system may not be the best one for your laptop. Operating systems vary in their use of power management, security encryptions (in case your laptop is stolen) and cost.
RAM
With all of the options out there, you may be wondering how much memory you need in your laptop. You should probably buy a laptop with a minimum of 64 MB RAM. Also, check to see how much VRAM you have, because this will be important in running graphics (minimum = 2 MB VRAM). Some laptops allow you to upgrade memory, and may have an easy access panel that provides for convenient switching of memory chips. In other upgradeable laptops, you have to open the case to get under the keyboard to add memory, or send it to a repair technician.
Keyboard
Because space is a premium for laptops, their keyboards tend to be smaller than desktop keyboards. Although you won't find an ergonomic keyboard, like the Microsoft natural keyboard, on a laptop, most laptop keyboards have some ergonomic features, such as being located at the back half of the unit to provide wrist support. The arrow keys will most likely be in different places to conserve space, and you may not have a numeric keypad. If you can, try out several laptops to see if the keyboards feel comfortable; this is especially important for touch typists.
Size and Weight
The size of the laptop is an important feature, seeing as the key advantage of a laptop is its portability. Consider the length, width and thickness, and make sure it will fit in whatever you plan to carry it around in, if you have something in mind. If you can, when you are shopping for your laptop, pick it up and carry it as you would a notebook. Does it feel comfortable?
Like size, weight is an important feature. Laptops vary in weight from 4 to 10 lb (2 to 5 kg). If you will be traveling frequently, you will probably want a light laptop (under 5 lb or 2 kg). Again, pick up the laptop that you are interested in. Can you carry it easily?
Case
Because you'll be carrying the laptop, there's a chance that you'll eventually drop it. Find out what material the manufacturer uses for the case. For example, the IBM Thinkpad has a titanium composite cover. This is a hard criteria to test out (the store won't be happy if you drop every laptop you're interested in), but it would still be useful to know.
Feel
Again, check out several models of laptops before you buy. Does the keyboard feel comfortable in combination with the input device? Is the screen large enough to see easily? We have talked about individual features separately, but it is important to check them out together to assess the overall feel of the model. Comfort is key in a laptop.
Software
Keep in mind what you intend to use your laptop for when you're shopping. Many laptops have software packages pre-installed or included in the box. Most tend to be word processing software, like Microsoft Word, or integrated software such as Microsoft Works or ClarisWorks. Check to see if the included software matches your needs; otherwise, you may have to spend several hundred dollars extra to get the appropriate software. Also, does the computer have sufficient memory and microprocessor speed to run the software you plan to use?
Carrying Case
Although carrying cases are not standard with laptop computers, consider spending the extra money to purchase a good one. Look for a carrying case that has the following features:
- lightweight
- rests comfortably on your shoulder (padded shoulder strap)
- waterproof or water-resistant (after all, you may have to walk in the rain)
- has enough space for your computer and accessories (disk drives, disks, AC adapter)
- has a padded compartment to protect the laptop should you drop the carrying case
Cost
Laptop computers vary in price from about $1,000 to ,000 or more, depending on the various features. Low-end laptops range from $1,200 to $1,600. Many retailers are offering to in rebates if you contract with a particular Internet service provider (ISP). If you do not have a current ISP, this might be a reasonable way to reduce the cost of your laptop. Note that the contracts usually lock you into one particular provider for two to three years.
When You Shop
We've created a Laptop Feature Comparison chart for you to use as you research various models. Take it to the store with you and fill in the blanks for each model you are interested in. You may also want to keep an additional copy near your desk as you research models on the Internet.
Look Out!
When buying a laptop computer, there are several things you should keep in mind to avoid buying one that won't meet all your needs. Here are some of the most important things to think about:
Make sure the microprocessor meets your needs.
If you will be doing lots of graphics or programming, you will probably need the speed of the most powerful processor available at the time. If you will use your laptop for basic word-processing, Web browsing or office management, then the AMD or Celeron microprocessors will be fine.
The latest operating system may not be the best for your laptop.
Operating systems vary in their use of power management, security encryptions (in case your laptop is stolen) and cost. The best operating system for a desktop may not be the best operating system for a laptop. Make sure you have at least 64 MB of RAM.
Look for easily upgradeable memory.
Does your laptop have an easy access panel to get at the memory chips? Do you have to open the case to get under the keyboard to add memory? Do you have to send it to a repair technician?
Know your battery life!
Your battery is essential to the portability of your laptop. Batteries will die. You will need a minimum of two hours of battery life; of course, four hours is even better. The battery life varies depending on what type of rechargeable battery you use (lithium batteries tend to hold their charge longer and have no memory effect) and how you use your computer (frequent use of disk drives consume lots of battery power). Also, look at the battery gauge in your software frequently so that you are not in the middle of some important project when your battery dies.
Count the input/output ports.
Computers send and receive information through various input/output ports, which can include serial ports, parallel ports and Universal Serial Bus (USB) ports. At minimum, you should have a printer port, which is usually a parallel port, and one or two USB ports.
One or two PC slots will help extend the life of your laptop by allowing you to upgrade rather than replace your laptop in the future.
Look for an internal fax/modem!
If you have to communicate with your company or customers while on the road, access e-mail, fax documents or access the Internet, then you will need a modem. Look for a laptop with an internal fax/modem (minimum 56 kps), because lugging a modem around with you is far from ideal. Adding a wireless card will allow you to accsess the Internet with a wireless connection.
Test out the input device.
Laptops use either a trackball, trackpoint or touch-pad to move the cursor across the screen. All of these devices have buttons that act like the right and left buttons on a mouse. The type of device you choose is totally a matter of personal preference. Some people prefer the feel of a trackball to a touch pad. If you can, try out the various input devices to see what feels right for you. Remember, most laptops have a port that allows you to hook up a mouse to your laptop, if you wish, but that will be another device to carry around if you want to use it on the go.
Check the feel of the keyboard.
Laptop keyboards tend to be smaller than desktop keyboards. If you can, try out several laptops and see if the keyboards feel comfortable to you; this is especially important for touch typists.
Look at the software.
Keep in mind what you intend to use your laptop for when you buy it. Many laptops have software packages pre-installed or included in the box. Most tend to be word processing software (Microsoft Word) or integrated software (such as Microsoft Works or ClarisWorks). Check to see if the included software matches your needs; otherwise, you may have to spend several hundred dollars extra to get the appropriate software. Also, does the computer have sufficient memory and microprocessor speed to run the software you intend to use?
Check the warranty
Read the fine print. A good warranty will cover parts and labor for three years. Also, toll-free, around-the-clock technical support is great. Some warranties may have a 24-hour replacement/repair policy (good when you are away from home). If these features are not in your warranty, consider a supplemental extended service contract.
Keep your laptop with you!
Do not entrust your laptop to baggage claim on the airlines -- you will run a high risk of damage. Also, laptop computers are prime targets for thieves. They are easy to carry off and easy to resell.
Manufacturers
FAQ
What is the best microprocessor?
If you do lots of graphics (computer-aided drafting, engineering design) or programming, then you will probably need the speed of a Pentium III or G4 microprocessors. On the other hand, if you will use your laptop for basic word-processing, Web browsing or office management, then the AMD or Celeron microprocessors will be fine.
How much memory do I need?
You should have at least 64 MB of RAM. Check to see whether your memory is upgradeable. If so, then your laptop should have an easy access panel to get at the memory chips.
How long will my battery last?
You should look for a laptop with a lithium battery, because lithium batteries tend to hold their charge longer than nickel-cadmium or nickel-metal hydride batteries, and have no memory effect. Whatever battery you choose, you will need a minimum of two hours of battery life; but of course, four hours is even better. The battery life varies depending on what type of rechargeable battery you have and how you use your computer (frequent use of disk drives consumes a lot of battery power).
How much space should my hard drive have?
All laptops have an internal hard disk drive, usually 6 to 20 GB (10 GB is a reasonable storage capacity).
What other drives should I have in my laptop?
You should have at least a standard floppy drive; you may want a higher capacity Zip drive as well. Also, if you want to be able to play music or movies on your laptop, you'll need a CD-ROM or DVD-ROM drive.
What is a swappable drive?
To make the laptop smaller and lighter, many models have "swappable" or interchangeable drives. With a swappable drive, there is only space in the case for one drive (floppy drive, Zip drive or CD/DVD drive). If you want to change from one type of disk drive to another, you just pull one out of the bay and put the other one in. In some laptops with swappable drives, you must turn the computer off first, change the drive and then reboot the computer. Other laptop models may have a "hot swappable" drive, in which you can interchange the drives without turning the computer off; this feature saves you the time involved in restarting the computer. While swappable drives allow you to use several types of drives in your laptop, remember that you will have to carry those extra drives with you if you want to use them on the go.
What type of screen should I get?
Large LCD screen sizes, active matrix displays and backlighting will make your laptop's screen easier to see, but these technologies will also increase the price of the computer. A 13- to 14-inch, active matrix, color screen is worth the investment, especially if you plan to search the Internet often or make multimedia presentations.
What type of input/output ports should my laptop have?
Computers send and receive information through various input/output ports, which can include serial ports, parallel ports and Universal Serial Bus (USB) ports. At minimum, you should have a printer port, which is usually a parallel port, and one or two USB ports.
What is a PC card slot?
In addition to ports, some laptops have expansion slots for PCMIA standard adapter cards (Type I and Type II) or "PC " cards. These cards can be used to upgrade your laptop by adding memory, a modem, a network connection or a peripheral device (such as a CD-ROM drive). One or two PC slots will help extend the life of your laptop by allowing you to upgrade rather than replace your laptop in the future.
What is a docking station?
If you will use your laptop as a desktop as well, you may want to look for a docking station. With the docking station, you can connect several peripheral devices (full-size computer monitor, full-size keyboard, mouse, disk drives, printer) permanently. You just plug your laptop into the station, and you're ready to use it as a desktop computer; in other words, you make one connection to your laptop instead of many. Most laptops have a docking connection.
Which type of input device is the best?
Laptops use either a trackball, trackpoint or touchpad technology to move the cursor across the screen. All of these devices have buttons that act like the right and left buttons on a mouse. The type of device you choose in a matter of personal your preference. Some people prefer the feel of a trackball to a touch pad. If you can, try various input devices out to see what feels right for you. Remember, most laptops have a port that allows you to hook up a mouse to your laptop, if you wish, but that will be another device to carry around if you want to use it on the go.
Do I need to buy a carrying case?
A carrying case provides a single place to store your laptop and its accessories. If you travel frequently, you will definitely need one. Look for a carrying case that has the following features:
- lightweight
- fits comfortably on your shoulder (padded shoulder strap)
- waterproof or water-resistant (After all, you may have to walk in the rain.)
- has enough space for your computer and accessories (disk drives, disks, AC adapter)
- has a padded compartment to protect the laptop should you drop the carrying case
Should I buy an extended warranty?
Read the fine print of your warranty. A good warranty will cover parts and labor for three years. Also, toll-free, around-the-clock technical support is great. Some warranties have a 24-hour replacement/repair policy (good when you are away from home). If these features are not in your warranty, consider a supplemental extended service contract.
Cool Facts
- NASA uses a specialized model of the IBM Thinkpad (running Microsoft Windows 95) for work in the space shuttle and in the International Space Station.
- Apple's Air Port technology allows I-Book laptops, along with Apple desktops, to connect to the Internet over a wireless connection at a high speed.
- Compaq now offers an Eddie Bauer model laptop computer, just as Ford offers Eddie Bauer model vehicles.
- New laptop computers can weigh as little as 3.75 lbs (1.7 kgs).
- Many newer laptops come with pre-assigned buttons that automatically control a CD player or MP3 playing functions.
|
|
How Motherboards Work
The motherboard has been an integral part of most personal computers for more than 20 years. Think of a motherboard as a scale model of a futuristic city with many modular plug-in buildings, each using power from a common electrical system. Multiple-lane highways of various widths transport data between the buildings. The motherboard is the data and power infrastructure for the entire computer.
Motherboards (also called mainboards) are actually a carryover from architecture used for years in mainframe computers. Various circuit cards performing various functions all plug into many similar sockets on a common circuit board. Each circuit card performs a unique function in the computer and gets its power from the socket.
Due to improvements in circuitry and packaging, motherboards have essentially stayed the same size or shrunk while their functionality has skyrocketed. In this article, you will learn how the motherboard operates and what its many sockets and connectors do.
Background
The original IBM PC contained the original PC motherboard. In this design, which premiered in 1982, the motherboard itself was a large printed circuit card that contained the 8088 microprocessor, the BIOS, sockets for the CPU's RAM and a collection of slots that auxiliary cards could plug into. If you wanted to add a floppy disk drive or a parallel port or a joystick, you bought a separate card and plugged it into one of the slots. This approach was pioneered in the mass market by the Apple II machine. By making it easy to add cards, Apple and IBM accomplished two huge things:
ط·آ·ط¢آ·ط·آ¢ط¢آ·ط·آ·ط¢آ¢ط·آ¢ط¢آ·ط·آ·ط¢آ·ط·آ¢ط¢آ¢ط·آ·ط¢آ¢ط·آ¢ط¢آ¢ط·آ·ط¢آ·ط·آ¢ط¢آ·ط·آ·ط¢آ¢ط·آ¢ط¢آ¢ط·آ·ط¢آ·ط·آ¢ط¢آ¢ط·آ·ط¢آ¢ط·آ¢ط¢آ· They made it easy to add new features to the machine over time.
ط·آ·ط¢آ·ط·آ¢ط¢آ·ط·آ·ط¢آ¢ط·آ¢ط¢آ·ط·آ·ط¢آ·ط·آ¢ط¢آ¢ط·آ·ط¢آ¢ط·آ¢ط¢آ¢ط·آ·ط¢آ·ط·آ¢ط¢آ·ط·آ·ط¢آ¢ط·آ¢ط¢آ¢ط·آ·ط¢آ·ط·آ¢ط¢آ¢ط·آ·ط¢آ¢ط·آ¢ط¢آ· They opened the computer to creative opportunities for third-party vendors.
Different motherboards of different vintages typically have different form factors. The form factor is essentially the size, shape and design of the actual motherboard. There are more than a half-dozen form factors for motherboards -- check out PC Guide's Motherboard Form Factors to find out about the various designations.
The motherboard, by enabling pluggable components, allows users to personalize a computer system depending on their applications and needs.
On the Motherboard
A motherboard is a multi-layered printed circuit board. Copper circuit paths called traces that resemble a complicated roadmap carry signals and voltages across the motherboard. Layered fabrication techniques are used so that some layers of a board can carry data for the BIOS, processor and memory buses while other layers carry voltage and ground returns without the paths short-circuiting at intersections. The insulated layers are manufactured into one complete, complex sandwich. Chips and sockets are soldered onto the motherboard.
Examples
The MSI 694D Pro AR supports dual Pentium microprocessors, has five PCI slots and a communications network riser (CNR) slot. The board supports 133 MHz bus speeds and ultra-direct memory access-100 (UDMA). There are four USB ports and onboard audio in the ATX form factor board.
MSI 694D Pro AR Dual Flip Chip Socket 370 motherboard
|
The Abit KT-7A supports Advanced Micro Devices (AMD) processors and has the KT-133A chipset. The card slots on the Abit KT-7A, from bottom to top in the image below, shows that ISA has one slot, PCI has six slots and AGP has one slot. A special fan cools the chipset.
Abit KT-7A AMD Processor Motherboard
|
A partial view of the TechRam S3ProM motherboard shows slots: From bottom to top, ISA has one slot, PCI has two slots, audio modem riser (AMR) has one slot, and AGP has one slot.
TechRam S3ProM Motherboard
|
The BIOS chip is common to many motherboards.
BIOS Chip |
Data Bus Width
Modern Pentium class motherboards have a data bus with 64 bits. That is the width of the data highway that goes in and out of the processor. The Pentium processors, however, do use 32-bit registers to handle 32-bit instructions.
Bus speeds and widths have increased due to faster processors and the needs of multimedia applications. Typical bus names and widths are:
- Industry Standard Architecture (ISA) - 8 or 16 bits
- Extended Industry Standard Architecture (EISA) - 8 or16 bits
- Microchannel Architecture (MCA) - 16 or 32 bits
- VESA Local Bus (VLB) - 32 bits
- Peripheral Component Interconnect (PCI) - 32 or 64 bits
- Accelerated Graphics Port (AGP ) - 32 bits
Chipsets
Chipsets provide the support for the processor chip on the motherboard. The Intel 440BX is the dominant chipset in the non-Apple personal computers. The chipset is the heart of the computer since it controls and determines how fast and which type of processor, memory, and slots are used. Another chip on the motherboard is called the Super I/O controller. Its main function is to control the floppy disk drive, keyboard, mouse, serial and printer ports. Check out PCGuide's Super I/O Controller Functions to learn more.
Recent motherboard designs include additional chips to support USB, sound card, video adapter, computer host and network adapter. These chips save the cost of an adapter slot.
Fans
Speeds, temperatures, density, faster chipset designs and component count have driven the need for circuit cooling via miniature electric fans. These fans mount inside the actual computer case. Heat sinks act like a car radiator, providing additional surface area to help cool a component.
Replaceable fan/heat-sink assemblies are often used to help dissipate the considerable amount of heat on modern processor chips. The assembly conducts heat away from the chip by convection, using a layer of thermal grease between the two mating metal surfaces. Fans often have a third wire used for monitoring the speed of the fan.
How Computer Memory Works
When you think about it, it's amazing how many different types of electronic memory you encounter in daily life. Many of them have become an integral part of our vocabulary:
- RAM
- ROM
- Cache
- Dynamic RAM
- Static RAM
- Flash memory
- Memory Sticks
- Virtual memory
- Video memory
- BIOS
You already know that the computer in front of you has memory. What you may not know is that most of the electronic items you use every day have some form of memory also. Here are just a few examples of the many items that use memory:
- Cell phones
- PDAs
- Game consoles
- VCRs
- TVs
Each of these devices uses different types of memory in different ways!
In this article, you'll learn why there are so many different types of memory and what all of the terms mean.
Memory Basics
Although memory is technically any form of electronic storage, it is used most often to identify fast, temporary forms of storage. If your computer's CPU had to constantly access the hard drive to retrieve every piece of data it needs, it would operate very slowly. When the information is kept in memory, the CPU can access it much more quickly. Most forms of memory are intended to store data temporarily.
As you can see in the diagram above, the CPU accesses memory according to a distinct hierarchy. Whether it comes from permanent storage (the hard drive) or input (the keyboard), most data goes in random access memory (RAM) first. The CPU then stores pieces of data it will need to access, often in a cache, and maintains certain special instructions in the register. We'll talk about cache and registers later.
The PC Process
All of the components in your computer, such as the CPU, the hard drive and the operating system, work together as a team, and memory is one of the most essential parts of this team. From the moment you turn your computer on until the time you shut it down, your CPU is constantly using memory. Let's take a look at a typical scenario:
- You turn the computer on.
- The computer loads data from read-only memory (ROM) and performs a power-on self-test (POST) to make sure all the major components are functioning properly. As part of this test, the memory controller checks all of the memory addresses with a quick read/write operation to ensure that there are no errors in the memory chips. Read/write means that data is written to a bit and then read from that bit.
- The computer loads the basic input/output system (BIOS) from ROM. The BIOS provides the most basic information about storage devices, boot sequence, security, Plug and Play (auto device recognition) capability and a few other items.
- The computer loads the operating system (OS) from the hard drive into the system's RAM. Generally, the critical parts of the operating system are maintained in RAM as long as the computer is on. This allows the CPU to have immediate access to the operating system, which enhances the performance and functionality of the overall system.
- When you open an application, it is loaded into RAM. To conserve RAM usage, many applications load only the essential parts of the program initially and then load other pieces as needed.
- After an application is loaded, any files that are opened for use in that application are loaded into RAM.
- When you save a file and close the application, the file is written to the specified storage device, and then it and the application are purged from RAM.
In the list above, every time something is loaded or opened, it is placed into RAM. This simply means that it has been put in the computer's temporary storage area so that the CPU can access that information more easily. The CPU requests the data it needs from RAM, processes it and writes new data back to RAM in a continuous cycle. In most computers, this shuffling of data between the CPU and RAM happens millions of times every second. When an application is closed, it and any accompanying files are usually purged (deleted) from RAM to make room for new data. If the changed files are not saved to a permanent storage device before being purged, they are lost.
The Need for Speed
One common question about desktop computers that comes up all the time is, "Why does a computer need so many memory systems?" A typical computer has:
- Level 1 and level 2 caches
- Normal system RAM
- Virtual memory
- A hard disk
Why so many? The answer to this question can teach you a lot about memory!
Fast, powerful CPUs need quick and easy access to large amounts of data in order to maximize their performance. If the CPU cannot get to the data it needs, it literally stops and waits for it. Modern CPUs running at speeds of about 1 gigahertz can consume massive amounts of data -- potentially billions of bytes per second. The problem that computer designers face is that memory that can keep up with a 1-gigahertz CPU is extremely expensive -- much more expensive than anyone can afford in large quantities.
In the next section, you'll find out how designers addressed this cost problem.
Memory Tiers
Computer designers have solved the cost problem by "tiering" memory -- using expensive memory in small quantities and then backing it up with larger quantities of less expensive memory.
The cheapest form of read/write memory in wide use today is the hard disk. Hard disks provide large quantities of inexpensive, permanent storage. You can buy hard disk space for pennies per megabyte, but it can take a good bit of time (approaching a second) to read a megabyte off a hard disk. Because storage space on a hard disk is so cheap and plentiful, it forms the final stage of a CPUs memory hierarchy, called virtual memory.
The next level of the hierarchy is RAM. We discuss RAM in detail in How RAM Works, but several points about RAM are important here.
The bit size of a CPU tells you how many bytes of information it can access from RAM at the same time. For example, a 16-bit CPU can process 2 bytes at a time (1 byte = 8 bits, so 16 bits = 2 bytes), and a 64-bit CPU can process 8 bytes at a time.
Megahertz (MHz) is a measure of a CPU's processing speed, or clock cycle, in millions per second. So, a 32-bit 800-MHz Pentium III can potentially process 4 bytes simultaneously, 800 million times per second (possibly more based on pipelining)! The goal of the memory system is to meet those requirements.
A computer's system RAM alone is not fast enough to match the speed of the CPU. That is why you need a cache (discussed later). However, the faster RAM is the better. Most chips today operate with a cycle rate of 50 to 70 nanoseconds. The read/write speed is typically a function of the type of RAM used, such as DRAM, SDRAM, and RAMBUS. We will talk about these various types of memory later.
First, let's talk about system RAM.
System RAM
System RAM speed is controlled by bus width and bus speed. Bus width refers to the number of bits that can be sent to the CPU simultaneously, and bus speed refers to the number of times a group of bits can be sent each second. A bus cycle occurs every time data travels from memory to the CPU. For example, a 100-MHz 32-bit bus is theoretically capable of sending 4 bytes (32 bits divided by 8 = 4 bytes) of data to the CPU 100 million times per second, while a 66-MHz 16-bit bus can send 2 bytes of data 66 million times per second. If you do the math, you'll find that simply changing the bus width from 16 bits to 32 bits and the speed from 66 MHz to 100 MHz in our example allows for three times as much data (400 million bytes versus 132 million bytes) passing through to the CPU every second.
In reality, RAM doesn't usually operate at optimum speed. Latency changes the equation radically. Latency refers to the number of clock cycles needed to read a bit of information. For example, RAM rated at 100 MHz is capable of sending a bit in 0.00000001 seconds, but may take 0.00000005 seconds to start the read process for the first bit. To compensate for latency, CPUs uses a special technique called burst mode.
Burst Mode and Pipelining
Burst mode depends on the expectation that data requested by the CPU will be stored in sequential memory cells. The memory controller anticipates that whatever the CPU is working on will continue to come from this same series of memory addresses, so it reads several consecutive bits of data together. This means that only the first bit is subject to the full effect of latency; reading successive bits takes significantly less time. The rated burst mode of memory is normally expressed as four numbers separated by dashes. The first number tells you the number of clock cycles needed to begin a read operation; the second, third and fourth numbers tell you how many cycles are needed to read each consecutive bit in the row, also known as the wordline. For example: 5-1-1-1 tells you that it takes five cycles to read the first bit and one cycle for each bit after that. Obviously, the lower these numbers are, the better the performance of the memory.
Burst mode is often used in conjunction with pipelining, another means of minimizing the effects of latency. Pipelining organizes data retrieval into a sort of assembly-line process. The memory controller simultaneously reads one or more words from memory, sends the current word or words to the CPU and writes one or more words to memory cells. Used together, burst mode and pipelining can dramatically reduce the lag caused by latency.
So why wouldn't you buy the fastest, widest memory you can get? The speed and width of the memory's bus should match the system's bus. You can use memory designed to work at 100 MHz in a 66-MHz system, but it will run at the 66-MHz speed of the bus so there is no advantage, and 32-bit memory won't fit on a 16-bit bus.
Cache and Registers
Even with a wide and fast bus, it still takes longer for data to get from the memory card to the CPU than it takes for the CPU to actually process the data. Caches are designed to alleviate this bottleneck by making the data used most often by the CPU instantly available. This is accomplished by building a small amount of memory, known as primary or level 1 cache, right into the CPU. Level 1 cache is very small, normally ranging between 2 kilobytes (KB) and 64 KB.
The secondary or level 2 cache typically resides on a memory card located near the CPU. The level 2 cache has a direct connection to the CPU. A dedicated integrated circuit on the motherboard, the L2 controller, regulates the use of the level 2 cache by the CPU. Depending on the CPU, the size of the level 2 cache ranges from 256 KB to 2 megabytes (MB). In most systems, data needed by the CPU is accessed from the cache approximately 95 percent of the time, greatly reducing the overhead needed when the CPU has to wait for data from the main memory.
Some inexpensive systems dispense with the level 2 cache altogether. Many high performance CPUs now have the level 2 cache actually built into the CPU chip itself. Therefore, the size of the level 2 cache and whether it is onboard (on the CPU) is a major determining factor in the performance of a CPU. For more details on caching,
A particular type of RAM, static random access memory (SRAM), is used primarily for cache. SRAM uses multiple transistors, typically four to six, for each memory cell. It has an external gate array known as a bistable multivibrator that switches, or flip-flops, between two states. This means that it does not have to be continually refreshed like DRAM. Each cell will maintain its data as long as it has power. Without the need for constant refreshing, SRAM can operate extremely quickly. But the complexity of each cell makes it prohibitively expensive for use as standard RAM.
The SRAM in the cache can be asynchronous or synchronous. Synchronous SRAM is designed to exactly match the speed of the CPU, while asynchronous is not. That little bit of timing makes a difference in performance. Matching the CPU's clock speed is a good thing, so always look for synchronized SRAM.
The final step in memory is the registers. These are memory cells built right into the CPU that contain specific data needed by the CPU, particularly the arithmetic and logic unit (ALU). An integral part of the CPU itself, they are controlled directly by the compiler that sends information for the CPU to process.
Types of Memory
Memory can be split into two main categories: volatile and nonvolatile. Volatile memory loses any data as soon as the system is turned off; it requires constant power to remain viable. Most types of RAM fall into this category.
RAM memory modules
From the top: SIMM, DIMM and SODIMM
|
Nonvolatile memory does not lose its data when the system or device is turned off. A number of types of memory fall into this category. The most familiar is ROM, but Flash memory storage devices such as CompactFlash or SmartMedia cards are also forms of nonvolatile memory. See the links below for information on these types of memory.
ROM memory module
|
|
|
