Desktop computers are the natural choice when a computer remains in the same place for all of its working life. The modular design of a desktop system makes it relatively easy to configure it with exactly the right set of features and functions for your specific needs. And if you expect to perform your own work, a computer in a desktop case is much easier to repair and modify than a laptop.
On the other hand, a desktop computer with its separate keyboard, mouse, monitor, and speakers is big, bulky, and awkward to move around.
When price is most important, a desktop computer is the better choice because a desktop computer almost always costs less than a laptop with comparable performance. Even after you add the price of a separate monitor, keyboard, and mouse to the basic system, the total is probably lower than a laptop with the same features. If you're looking for the least expensive computer you can buy, or the least expensive computer at a specific level of performance, a desktop system is the clear choice.
Of course, it is possible to spend more for a desktop computer than the price of a good laptop by choosing a super-fast processor and graphics controller, lots of memory, a large flat-panel monitor, and other high-end components and features, but that's not a fair comparison. The price of a desktop system is always far less than a laptop machine with similar specifications.
If you can assemble your own computer from parts, the savings can be even greater. Major computer builders such as Dell and Hewlett-Packard may offer very inexpensive models with limited performance (including slow processors, limited memory and low-capacity hard drives) for less than the cost of assembling a similar machine yourself, but if you want a system with better performance, you can often find higher-quality parts for less than the cost of an off-the-shelf product. Cases, motherboards, disk drives, expansion cards, and other standard parts for desktop computers are easy to find, so building your own system can be a practical alternative for people who have more time and assembly skills than ready cash, and who want something better than an entry-level system. But there are no widespread standards for the size and layout of laptop components, so it's not always practical to look for a generic laptop case, keyboard, video display, and motherboard that you can put together yourself.
See Chapter 4 for more details about motherboards, expansion cards, and other important parts of your computer.
As explained later in this book, the parts inside a desktop computer usually follow one or more design standards, so it's often possible to replace a component that fails with a new one from a different manufacturer. And when you want to add more memory, a larger hard drive, or maybe a second graphics controller and monitor to your system, you can be confident that you won't have to limit yourself to products from a single manufacturer. Just because the label on the case says Compaq or Gateway (or Ye Olde Neighborhood Computer Shoppe), you can still go to a big-box retailer such as Fry's or CompUSA or an online source such as Newegg and choose from among many different brands. This combination of modular design and competition is one reason that the prices of most desktop computer components are lower than the comparable, non-standard parts in a laptop.
In addition, the common parts specifications allow a repair shop to maintain a smaller inventory because they can use the same parts in many different desktop computer makes and models.
Desktop computers are modular systems that make it easy to add or replace individual parts to meet each user's particular requirements. A computer intended for an illustrator or a computer-aided designer might have a higher-quality graphics controller and video display than the one in the next office, where a purchasing agent may not use anything more demanding (of computer resources) than a word processor and a spreadsheet. Most computer manufacturers let you order exactly the set of features and specifications that you want.
When your needs change, it's usually easy to open up a desktop case and reconfigure the system, unless your computer uses proprietary parts. You can be confident that the sockets on the motherboard and the mounting holes in the drive bays fit the new expansion card or disk drive, and the main printed circuit board that controls the rest of the system (the motherboard) works with the new parts.
Modular design also means that you can transfer some old parts to your new computer when you replace your Old Faithful machine that has finally become obsolete. For example, I wrote this book on an old Northgate keyboard that I have moved from one computer to the next for more than fifteen years; I like the way its keys respond to my typing. Northgate stopped making these keyboards many years ago (similar keyboards are still available from other makers, but they're very expensive), but the plug on the keyboard's cable still fits the socket on my current computer and it works just fine with a twenty-first century processor and motherboard.
Of course, there are some limits to this flexible design. You can't use a brand-new memory module or the latest disk drives with a 10-year-old motherboard because the designs have changed to accommodate newer and better processors and other devices.
You can improve the computer's performance by adding new components and replacing existing parts with new ones that have faster speed, greater capacity, or more features. Once again, the desktop computer's modular design makes it easy to work inside the case. Of course, there's a point of diminishing returns where it's better and less costly to buy a new system, but just about every desktop computer has room for economical improvement.
The most common and effective way to improve a computer's performance is to add memory. In both desktop and laptop systems, the motherboard has one or more sockets for memory modules, so you can increase the total amount of memory by adding one or more new modules to the memory that is already in place. You can also remove the existing memory and replace it with the same number of modules with more memory on each module. Adding memory is easier in a desktop system because there's plenty of space inside the case.
Except for a few very small cases, all desktop computers have two or more internal drive bays. Therefore, you can add storage capacity by installing another hard drive to the system simply by mounting the drive in a vacant drive bay and connecting a couple of cables. It's not necessary to transfer the data already stored on the existing drive first.
The CPU chip in a desktop system-the central processing unit that controls everything else-is also relatively easy to remove and replace with a faster CPU with similar architecture, and that fits in the same socket. A new CPU can offer faster processing and better performance than the one that was originally supplied with the computer. Unlike most of the other integrated circuits on the motherboard, the CPU mounts in a special socket that uses a latching mechanism to hold it in place, so it's not necessary (or possible) to solder a new chip directly to the printed circuit board.
All of these upgrades are easy to perform, but they often require some changes to the computer's hardware or software configuration. Before you try an upgrade, consult the computer manual or the motherboard manual for information about jumpers or switch settings on the motherboard, and adjustments to the BIOS settings (the BIOS-basic input/output system-is the set of programs the computer uses to test hardware and load Windows or some other operating system).
For more in-depth information about the CPU, the BIOS, and other PC components, see Chapter 4.
Repairs and modifications to desktop computers are not difficult because there's more space inside the case. As a result, their designers could use larger parts that are easier to find and easier to handle. Cables, connectors, printed circuits, and hard drives are all big enough to find without a magnifying glass, and big enough for people with average-sized hands to work with.
The modular structure of a desktop computer also contributes to its ease of repair. The most common troubleshooting methods include swapping parts to identify a bad component, and moving expansion cards and cables from hard drives to a different socket. This may not be possible on a laptop system with only a limited number of sockets.
Even the screws that hold things together are bigger inside a desktop case than the ones inside a laptop. Bigger screws are often easier to insert and remove, and they're always easier to find when you drop one on the floor (especially on a carpet). And the full-size screwdrivers, pliers, and nut-drivers are far less fiddly and are easier to handle than the smaller versions that are often needed to disassemble a laptop computer.
Desktop computers do have some drawbacks. A desktop case with a separate keyboard occupies more physical space than a more compact laptop computer. For most of us, the space on our desks, worktables, or kitchen counters is prime real estate, so a computer with a smaller footprint is highly desirable. This may be less of an issue today than it used to be, because flat-panel monitors are much less intrusive than the old cathode-ray tube displays that were often 18 inches or more from front to back.
It might be possible to reduce the physical impact of a desktop system through careful design and planning. You could place the main processor case on the floor or on a shelf, and use longer cables to connect it to the monitor, keyboard, mouse, and speakers; but that big box has to go someplace, and sometimes you need to reach the controls on the front panel, so you can't just seal the thing permanently inside a cabinet. There's a whole branch of the furniture industry dedicated to designing and selling tables, cabinets, media centers, and other objects with the intent of placing computers and other electronic equipment on, within, or under them. Even a company such as E.A. Clore, which has been making chairs, tables, and cabinets since 1830, offers a fine "early-American" computer table (see Figure 1.3).
Figure 1.3: It's an ugly modern computer, but the table can still fit your décor.
Desktop computers are big and heavy. If you ever have to move your desktop system with all its accessories and accouterments from one room to another, you probably want to use a cart with several shelves, or at least an office chair with wheels. Then you must find and attach at least half a dozen different cables to the back of the box or convince your local computer expert to do it for you before you can use the computer again. Moving a desktop computer is a complicated and time-consuming exercise.
If you're planning on moving your desktop computer several times, take care. Moves are sometimes blamed for system crashes.
Sometimes you don't have any choice about moving your computer around. Maybe you're a teacher or a librarian who uses the same machine in different rooms; or possibly you're running a conference that includes PowerPoint presentations in several different places. If that's your situation, and you can't replace the system with a portable, your best bet is to find or build some kind of special computer cart that holds everything in place with all the cables connected. When you arrive at the new location, you can plug the power cord into the wall and hope that all the other cables haven't shaken loose from their sockets. The computer is still big and heavy, but it doesn't have to be quite as inconvenient to move.
The electrical circuits, fan motors, and disk drives in your computer use DC power from the power supply inside the case. On the other hand, the power supply, along with your video display and other external accessories, needs a source of domestic AC power (110 volts in North America and Japan, 220 volts in most other places). If there isn't a wall outlet nearby, you need some kind of generator, or a big battery with an inverter, or an extremely long extension cord.
It's possible to replace the usual AC power supply with one that uses a 24-volt or 48-volt DC input, but DC power supplies for desktop computers are expensive and uncommon. A DC supply might be practical in a location that uses solar power, or in a telephone switching center that already has a room full of batteries, but every off-the-shelf desktop system you're likely to find comes with an AC power supply. If you can't provide it with a continuous source of AC power, you're out of luck.