If you're using a portable for extensive computing rather than as a simple memo and communications device, you'll want to evaluate the processor and memory capacity much as you would a desktop machine.
For machines built on the Intel architecture you can already get "Pentium with MMX" and processors running at over 200 MHz, but you'll have to wait until sometime later this year to get a Pentium II designed for portable use. A few machines use Intel's "Mobile Module" CPUs, which include a Pentium MMX chip, cache memory and PCI interface in a single module--which Intel says should be replaceable at some future date with a faster model. Although you don't need the MMX features for most current office applications, it will help out with most new and future multimedia programs.
Apple claims that its new "G3" PowerPC chip is even faster, with clock rates that match or exceed Intel's fastest Pentiums. But as with desktops, clock speed comparisons within a line are fairly indicative, but comparisons between different chip architectures don't necessarily reflect relative performance. You can also get more modest PowerBook portables with CPU's comparable to Intel's medium-speed chips.
Most portables require their own format for memory, and you usually pay a premium for it compared to the same chips configured for a desktop machine.
Internal hard disk drives are slightly more standardized, with some exchange between units. Capacities have already passed 6 gigabytes on some portables, although 1 to 3 gigabytes is more common. But the tiny 2-inch and smaller drives used in most portables aren't the commodity items of their larger desktop cousins, and consequently cost more for the same storage capacity.
If you're carrying a portable around in a shoulderbag all day, the most important feature by far will be weight. A few full-function portables weigh in under 2 pounds, but most weigh between 2 and 5 pounds. So-called "ultraportables" with reduced-size keyboards and small screens can run under 1 pound.
In other applications where you plan to use a portable machine away from mains power, battery life can be the most important characteristic. Typically, manufactures claim from 1 to 6 hours of running time.
In many offices a network connection is essential. Some portables have Ethernet built in, some have an Ethernet connection in a docking station, and Macintosh models have built-in LocalTalk. If you have a free PC Card slot, you can add a card for most common networks.
Modem links are provided in a similar assortment of internal, add-in, dock-based and PC Card-based configurations. Some portables even offer mounting brackets or cable connections to make it easy to connect their modem to a cellular phone or to use a wireless modem for truly portable connectivity.
Tradeoffs and Buying Advice
If you're looking for a particular software environment, you can choose a portable computer built to run any of the popular operating systems. However, except for some very specialized applications that require another system, it's likely you'll want either a Windows or MacOS-based system because of their lower cost and greater variety of software and accessories.
If you're matching a portable to a desktop machine, it's slightly easier to share files or set up networks between machines running the same operating system -- but popular programs for both types of machines usually include file translators.
As with desktop machines, you'll pay significantly more for a unit with the latest and fastest processor than one that's a bit further from the cutting edge.
While a fast processor speed has the same advantage in a portable machine as it does in a desktop system, it has a larger design tradeoff. Given the same basic design, running circuits faster consumes more electrical power and produces more heat. Since power is precious in a battery-operated machine and heat is hard to deal with in a compact box, a machine running at modest speeds may sometimes be a better fit. Consequently, if you're looking for a machine to use mostly on battery power, we suggest you go for one of the more moderate speed units, unless you need fast processing for particularly demanding applications and are willing to sacrifice running time. On the PC side, that might be a machine with a Pentium 133 or equivalent running under Windows (even a 33 MHz 486 will do fine for light duty under DOS). Apple has abandoned the low-end of the portables market, so you won't be able to get a machine with less than a 133 MHz PowerPC processor. On both sides, if you need more power you can more than double the processor speed and more than double the cost.
Similarly, extra RAM and a large hard drive both make it easier to use large and complex programs on a portable machine, but they also use extra power and cost more--although extra RAM can sometimes save power if it allows you to use the hard disk less frequently.
An initial memory complement of 16 megabytes and a maximum memory capacity of 16 to 32 megabytes may be enough for light-duty machines. Machines for more challenging applications may need double that amount.
Whether you want to pick the more economical passive matrix screen technology or the sharper but more costly active matrix approach is largely a matter of budget and personal preference. Some people perceive the difference as minor, while for others it's a major differentiation. If you're not sure, be sure to try out both technologies on the kind of files you're likely to be working with. You're most likely to notice the difference on moving images and pictures where you'll notice small color variations such as close-ups of faces.
Screen sizes for portable computers range from under 6-inches to more than 12-inches. Because the difficulty of making a flat screen goes up much faster than the size, the larger sizes are significantly more expensive. They're also more breakable. But if you expect to use a portable for long periods at a time, they can be worth the extra cost and risk. In any case, if you expect to run standard software you should look for a screen that shows at least 640 by 480 pixels--while software for both Windows and Macintosh is supposed to be independent of screen size, many programs do not display properly at lesser resolutions.
How large a hard disk you'll need depends on your applications. A few hundred megabytes will do fine for wordprocessing and email, but you could need up to several gigabytes for multimedia presentations, mobile databases or graphics work.
If you're going to be using your portable in the field, you'll want to pay particular attention to battery life. Unfortunately, there's an entire cult of batteries, battery chargers, "conditioners" and exotic battery technologies, but very little objective information. For example, although scientific tests generally find no evidence of a "memory effect" in modern nickel-cadmium batteries of this size range, many users swear they have to discharge this type of battery completely at regular intervals or it won't take a full charge.
We suggest you consider specified battery life claims as only rough guides rather than specific promises -- running time values supplied by manufacturers usually turn out to be optimistic when compared to average results in the field. The actual time depends heavily on how often your programs access the disk drive, whether you're using a power-saver mode that sacrifices performance for running time, and many other variables. If you need to work for long period away from mains power, you might want to look for models that have easily replaceable batteries or even a model that can also run off ordinary "flashlight" style batteries in a pinch. If you're using a portable at just two locations and you need to use external resources at each location, you may want to look for a model that offers a reasonably-priced docking station. That way, you can leave a docking station connected at each location rather than having to connect cables each time.
Only a few printers and portables have the IrDA system working yet, but it's a real convenience if you only need to print an occasional document and you don't want to dock the computer or hook up cables.
Finally, as with buying an automobile, style, fit and finish mean a lot more to some people than others. A keyboard layout or case style that's fine for your coworker can turn out to be a major irritant for you. If you plan to spend much time typing away on your portable or staring at the screen, make sure you either try out that model beforehand or buy where you can exchange a unit if necessary. Buying a unit that will provide you with the most pleasing working environment is crucial for long term satisfaction.
* Este material foi copiado da página da PCMagazime.
Contato: Marcos Dias de Moares