For the record, and just so there's no misunderstanding, you have some other choices if you want to use Wi-Fi besides buying a new laptop with Intel Centrino mobile technology. First, there are wireless Windows laptops that don't use Centrino, and you can add a Wi-Fi card to almost any existing laptop. Second, laptops from Apple also use Wi-Fi. (In the Apple universe, Wi-Fi is called Airport and Airport Extreme.) Finally, it is even possible to use Wi-Fi with a laptop using Intel Centrino mobile technology running Linux (rather than Windows), although this is probably more appropriate for advanced users.
Of course, Wi-Fi also works well with desktop computers.
But from the viewpoint of this book, my assumption is that you either own (or are looking to buy) a Windows laptop based on the Intel Centrino mobile technology. In particular, this chapter is about buying a laptop to use for mobile computing.
Laptops work in pretty much the same way as full-sized desktop computers\u-3945\'3fthey just come in a smaller package. Most everything is compressed into the small familiar form factor that you can carry around with you (unlike desktop computers, which typically feature separate display devices and system units).
So when you are learning about your future Mr. (or Ms.) Laptop Computer, you should know that (just like a desktop computer) your laptop will have
A system unit (which includes the central processing unit, or CPU)
A display device (laptop display devices are generally LCD, or liquid crystal display, screens)
Peripheral devices, probably including a pointing device such as a trackpad or stick mouse that takes the place of a mouse and likely including speakers for sound
The laptop form factor typically includes the system unit, the display, and peripheral devices including a keyboard and pointing devices all in the single small, lightweight package. Essentially, these elements in the laptop are no different from the elements in a desktop computer; it is the small package size, also called the form factor, that makes a laptop computer what it is.
Because they are comparatively miniaturized and require some special engineering features (such as the capability to run on low power), laptops are more expensive than comparable desktops.
The system unit is the part of the computer that makes it a computer. Just like its big brother, the desktop computer, the system unit in your laptop has a number of important components, including
A microprocessor, also called the central processing unit (CPU), which controls the entire computer.
Short-term storage, called random access memory (RAM), which is used to temporarily store instructions and information that can be used by the microprocessor.
Long-term storage, which is the hard disk used to permanently store important computer programs and data.
Devices used to get information in and out of the computer; for example, CD drives, diskette drives, network cards, and Wi-Fi cards.
Battery Life and Laptops
Unlike desktop computers, mobile laptops are battery powered. Laptop computers provide a recharging mechanism for the computer battery when the computer is plugged in. All new laptops sold today come with Lithium Ion batteriesa change from the Nickel-Cadmium battery days.
How long a mobile computer can run on its battery is very important to users because this determines how long the computer can be used without plugging it in to an electric socket. The ability to work without network wires, thanks to Wi-Fi, is kind of undermined if you have to plug in to a standard electrical outlet just to get power.
Many factors go in to Lithium Ion battery life, including the power drawn by the CPU and the power needs of the computer's peripherals. This is an area to investigate carefully before you buy your laptop, based on your needs. So review battery life specifications carefully before you buy. On some models, multiple batteries are an option for extending usage time, so if this is important to you, you should investigate the feature before you buy.
The Pentium M, which is part of the Intel Centrino mobile technology platform, is specially designed to be used in laptops because it has low power draws. (Of course, the CPU isn't the only laptop component that draws power.) You can check to make sure that the laptop you are considering uses one of the microprocessors specially designed for laptops.
Here are some tips for prolonging the life of a Lithium Ion laptop battery:
Make sure you plug in your laptop as often as possible. Unlike the older Nickel-Cadmium rechargeable batteries, Lithium Ion batteries do not have a memory effect. The memory effect, which occurred with Nickel-Cadmium batteries, resulted in a loss of battery capacity when the batteries were partially discharged and charged repeatedly. In Nickel-Cadmium batteries the memory effect could be overcome by one or more deep discharge/charge cycles. This was called battery conditioning. Battery conditioning is definitely not necessary with Lithium Ion batteries and it will not increase their capacity or capability to hold a charge. In fact, it will shorten the life of a Lithium Ion battery.
Limit the number of full charge to full discharge cycles. A Lithium Ion battery has a maximum life of 500 full cycles. This means that if you use your laptop on the train in the morning and fully drain the battery, recharge it, and then fully drain the battery again in the afternoon you have already used two full cycles. If a battery has only 500 full cycles and you use two full cycles every day, you ll need to replace the battery within six to eight months! With partial discharges, a Lithium Ion battery can last as long as 1,000 cycles.
Beware of fully discharging a Lithium Ion battery because the polarity within the battery cells could actually reverse and short circuit the battery.
It's likely that one of the things you ll focus on most when deciding which laptop to buy is the microprocessor. This makes sense because the speed of the CPU largely determines how fast the computer can perform operations.
With laptops, the CPU is particularly important. First of all, as I mentioned earlier, CPUs specially designed for use in laptops use less powerand therefore aren't as draining on battery life. Second, these microprocessorssuch as the Pentium M that is part of the Intel Centrino mobile technologydon't run as hot as CPUs intended for desktops.
You shouldn't even judge a CPU just on the basis of its speed. Many facets of the architecture of a CPU besides its raw speed can affect its performance. For example, a Pentium M (powering a system using the Intel Centrino mobile technology) running at about 1GHz performs on par with an Intel Pentium 4 desktop computer running at about 2GHz.
Just as brute brawn isn't everything in life, you probably would not be surprised to learn that the raw speed of the CPU isn't the only factor in how quickly a laptop performs its appointed tasks. For many applications, the amount of RAM available on the computer is actually more important than the CPU speed. In another example, for watching movies, besides the quality of the video screen, the most important hardware is the video display subsystem, not the CPU.