|
 |
|
|||
      |
For
Windows-based desktops, the major players are Intel and AMD. Intel
Celeron chips, available in speeds from 500 MHz to 766 MHz (66-MHz bus)
and 800 MHz to 850 MHz (100-MHz bus), and AMD Duron chips, available in
800 MHz to 900 MHz (200-MHz bus) versions, are low-cost processors
designed to keep desktop prices under $1,000 but still provide enough
power to handle popular home software and standard business
applications. Pentium III processors, running at speeds from 650 MHz to1
GHz, interface with 100-MHz or 133-MHz busses, depending on the chip.
These processors feature an improved cache architecture and special
instructions designed to improve the performance of streaming audio and
video, 3-D imaging, and speech recognition applications, with a view
toward enhancing the Web experience. Motorola's G3 processor for the
iMAC comes in 400-MHz, 500-MHz, and 600-MHz versions and plugs into a
100-MHz system bus. The Intel Pentium 4 and the AMD Athlon processors
are currently the fastest available, delivering speeds of up to 1.7 GHz
and 1.33 GHz, respectively. The Pentium 4 chip features what Intel calls
its NetBurst micro-architecture, which increases the bus speed to 400
MHz, adds over 100 new multimedia instructions, and moves information
through the processor faster. AMD Athlon processors provide bus speeds
of 200 MHz and 266 MHz, depending on the chip. They feature enhanced
3Dnow!, a technology designed for fast processing of the type of data
encountered by multimedia applications such as digital video and video
streaming. Motorola's G4 processor, which is used in Apple's Power Mac
G4 system, runs at speeds of up to 733 MHz and has a bus speed of 133
MHz.
Along with the processor, system memory is one of the most important determinants of your desktop's performance, because this memory holds the data the CPU needs to do its job. System memory comes in a variety of speeds, shapes, and sizes.
DRAM temporarily stores data and instructions used by the CPU (and other devices). The information is lost when the system shuts down. Earlier desktops used FPM (Fast Page Mode) and EDO (Extended Data-Out) RAM, but these were too slow to keep up with the faster processors, creating a bottleneck that prevented the CPU from performing at optimal speed.
SDRAM is the most common form of desktop memory used today, SDRAM is synchronized with the CPU's clock, so there is little or no downtime when transferring data to the processor. SDRAM is available in 8MB to 256MB DIMMS (dual in-line memory modules) and is up to four times faster than its predecessor, DRAM.
Developed by Rambus and Intel, this is some of the fastest system memory available for desktops. It transfers data at up to 600MHz. RDRAM is currently available in RIMMs of up to 256MB.
This memory is similar to SDRAM but twice as fast. Data is accessed two times per clock cycle as opposed to standard memory, which accesses data only once per cycle. DDR memory is available at speeds of 200 MHz and 266 MHz in 64MB to 1GB DIMMs.
ECC is a technology used in certain memory types, particularly SDRAM, that catches and corrects accidentally changed bits without stopping the system. ECC RAM costs more than non-ECC RAM and is used mostly in servers.
Commonly
referred to as the system board or main board, the motherboard is the
foundation upon which most computers are built. This is generally where
the CPU, memory, I/O controllers and connectors are mounted, and where
expansion boards are plugged in. The CPU, chip set (the collection of
microchips that contains the main controller circuitry), other
controller chips, and memory are connected by printed,
electrically-conductive traces that provide the highway over which data
and power are distributed among the system's components. Knowing what
type of motherboard is installed in your desktop is important if you
plan on adding expansion cards, memory, or additional processors at a
later date. Desktop motherboards are manufactured in several form
factors, depending on the desktop chassis, power supply, and the layout
of chipsets and slots.
Deciding which hard drive is best suited to your desktop will depend on several factors including speed, compatibility, and price. As far as storage space is concerned, more is better, but as the capacity of the hard drives rises, so does the price. For example, opting for a 60GB rather than a 20GB EIDE drive could cost another $100. An additional 9GB SCSI drive can cost over $200. The speed of your drive, as measured by its seek time and the rate of data transfer to and from the drive, will play an important role in the overall performance and cost of your desktop. Some common hard drive types are listed below.
ATA (AT
attachment) drives, commonly referred to by the acronym IDE (integrated
drive electronics), connect to the controller via a ribbon cable. Most
non-SCSI motherboards have an integrated controller and two connectors
capable of supporting a total of four EIDE (enhanced IDE) drives. The
ATA specification is currently in its third revision (ATA-3), and
features enhancements such as support for SMART (Self-Monitoring,
Analysis and Reporting Technology) and high-speed data transfer via
Ultra DMA (Direct Memory Access) modes.
SCSI is a
faster interface than IDE. SCSI drives are widely used in high-end
systems and cost more than IDE drives. Although most desktops include a
built-in IDE interface, SCSI drives usually require an add-in SCSI
controller. Besides speed, SCSI has the advantage of allowing numerous
devices to connect to one controller. Configuration, however, is
generally harder than with IDE.
This is not a drive type but rather a method for connecting several drives using a special controller. Data is stored across the array of drives simultaneously, according to one of several possible schemes, allowing for faster reads and writes and also enabling mirroring of drives, which provides a backup if a drives fails.
The most common forms of optical drives are CD-ROM and DVD-ROM. Almost all desktops ship with at least one of the two. The latest addition to the optical drive family is the combo drive, which integrates several different optical drives into one device. Most optical drives are available as internal devices and as external units and often come in IDE, SCSI, and USB versions.
These are used
for installing software and playing CD-based audio and video media.
These drives read at speeds as high as 52X (7.8MBps maximum data
transfer rate).
CD-RW drives are similar to CD-R drives but allow recording to CD-RW media, which can be erased and re-recorded. CD-RW drives will read standard CD media, although older CD-ROM drives may not be able to read CD-RW media.
This is a
read-only drive that supports DVD media, which are the same size as CDs,
but recorded on both sides and capable of holding far more information.
DVD drives are used to install and run large applications that
previously required multiple CDs. DVD drives will play DVD movies as
well, although an MPEG card or DVD software is suggested on slower PCs.
DVD discs hold up to 17GB of data.
This is a DVD drive with the ability to write to DVD-R media. DVD-R discs are write-once media (cannot be erased and rewritten). They can be played back on standard home and computer DVD players.
These drives
use special media enclosed in a cartridge, which cannot be used in
non-DVD-RAM drives. The media can be written to, erased, and rewritten
over 100,000 times and will hold over 4.7GB of data but are still fairly
expensive. DVD-RAM drives will read all CD and DVD media and are ideal
for storing files that tend to be large, such as those containing video,
and for backing up critical data.
Combo drives
offer an all-in-one solution. They can read from and write to CD-R and
CD-RW media and read DVD-ROM media as well. Although generally not as
fast as standalone drives, they use only one drive bay, conserving
space.
Other
removable-media devices are available. Two of the most popular for data
storage are Iomega Zip Drives and Iomega Jaz Drives.
These use
proprietary media similar to, but larger than those for Zip Drives. The
disks hold up to 2GB of data. Iomega Jaz 2GB 3-Pack here
If given the
opportunity to choose your display, consider the following factors:
display type (CRT or LCD), price, size, and most importantly,
resolution. If you configure your desktop with a video card capable of
1,600-by-1,024 resolution, make sure your monitor can handle that
resolution. For a more detailed look at displays, see the Displays
Buying Guide.
Pay special attention when choosing your video adapter, if you have the option of selecting one. Try to get a video card that will meet your current needs and that you can upgrade in accordance with your future plans.
This is the
type of card you'll want if you seek high-speed video performance.
Common uses include animation applications, gaming, and presentation
graphics. There are plenty of 3-D video cards to choose from, each one
more powerful than the next and as a rule, the more powerful the more
expensive. Most are capable of running at resolutions of up to
1,900-by-1,200. The amount and type of video RAM on the board affects
the cost, the graphics performance, and the quality of the image. For
gamers, a 64MB 4X AGP video card will do the trick, although bumping the
RAM up to 128MB won't hurt.
Not for your
typical desktop, these cards are usually found in workstations and other
high-performance systems and carry hefty price tags, sometimes in the
thousands of dollars. The cards generally rely on OpenGL architecture,
the premiere technology used by developers of high-end video cards due
to it's powerful rendering and texture-mapping capabilities, making this
class of video controller ideal for precision applications such as CAD,
medical imaging, and mechanical engineering.
Most desktops ship with some sort of audio hardware, either on-board (integrated on the motherboard) or in the form of a third-party sound card. As with most PC components, sound devices vary in functionality, features, and price.
Recent
advances in integrated sound hardware have resulted in good audio output
without the need for an additional sound card. This frees an expansion
slot for other peripherals. For a true multimedia system that will
deliver surround sound and other special audio effects, though, an
add-on sound card may be your best bet. Even though integrated sound has gotten better, there are advantages to using a third-party sound card. Integrated audio uses the CPU to process sound, but many third-party sound cards use their own Digital Signal Processor (DSP), freeing the CPU for other tasks. Also, add-in cards provide additional input and output connectors, allowing you to add up to six speakers.
There are several ways to connect peripheral devices such as printers, scanners, and modems, to your desktop. USB is the most recent, but IEEE 1394 (FireWire) is the current port of choice for peripherals, such as digital cameras, that transfer large amounts of data. Legacy (old technology) devices, which connect to parallel, serial, and PS/2 ports, are still popular, too. There are quite a few legacy devices in use and on the market.
Although
parallel, serial, and PS/2 devices are still widely used, newer
technologies are surpassing them. Most desktops still support these
ports, though. Parallel ports are mainly used for printers and external
storage devices, such as CD-ROM drives; serial ports are used to connect
modems and to hook up input devices such as mice; and PS/2 ports connect
keyboards, mice, and other pointing devices.
Most current
desktops contain several USB (Universal Serial Bus) ports, sometimes as
many as six. USB provides faster transfer rates (up to 12 Mbps) between
peripheral devices and systems than legacy ports, and USB devices are
fairly easy to install. Peripherals such as printers, digital cameras,
speakers, and external storage devices have adopted the USB standard.
Until
recently, Ethernet was used exclusively in the business arena as a means
of connecting multiple systems in a network. But connecting to
high-speed Internet services via cable or DSL requires devices that
communicate with your computer using Ethernet, so most system makers
offer Ethernet ports as an option, at least.
Based on the IEEE 1394 standard, FireWire is similar to USB in that it provides a high-speed serial connection between the peripheral device and the system. Capable of moving data at up to 400 Mbps, FireWire is the preferred method for transferring data between the desktop and devices such as camcorders and digital cameras. Consider FireWire if you're into video editing and other multimedia applications.
The ability to configure your desktop with additional expansion cards, such as network, video, and sound controllers, depends on the availability of unused expansion slots. Many slim desktops and small-form-factor systems have limited room for expansion. Mini-towers and full-size desktops often provide several open slots.
Desktops today
provide few, if any, expansion slots for ISA cards, although these cards
still exist on the market (there are still a lot of systems with ISA
slots out there). ISA has fallen into the legacy category due to its
slow bus speed (8 MHz) and narrow bus width (16 bits).
This is the standard bus architecture used in desktops today. PCI slots have direct access to system memory via a controller called a PCI bridge, use a wide bus (64 bits), and have bus speeds of up to 133 MHz.
Many machines include an AGP slot in addition to several PCI slots. The AGP slot is used exclusively for an AGP video controller card and provides a dedicated port for moving 3-D data from the controller to system memory at four times the speed of the PCI bus. This not only increases 3-D performance but also frees the PCI bus to move data to and from other devices.
The majority
of home desktops ship with Microsoft Windows Me, Microsoft's Millennium
Edition of Windows, which is geared toward the home-office and
small-office markets. Windows Me includes tools for managing, editing,
and sharing music, video, and digital images, as well as wizards for
setting up a home network. Most business desktops ship with Windows 2000
Professional, which is built on the Windows NT platform and uses a
Windows 98 interface for ease of use (Windows 98 and NT are still
available, also). Look for the latest OSs from Microsoft, Windows XP
Professional (for businesses) and Windows XP Home Edition, to ship later
this year.
The amount of
power used by a single desktop under normal operating conditions won't
drive your utility bills through the roof, assuming the system is turned
off when not in use. To cut down on system wear and tear and to ease
power consumption in general (there are a lot of PCs running out there),
the industry has developed several power-saving standards. APM (Advanced
Power Management), ACPI (Advanced Configuration and Power Interface),
and OnNow are good examples of how the OS and hardware components work
together to shut down or to enter a sleep mode when not in use and to
quickly resume operation when needed.
Most desktop manufacturers preinstall a suite of applications on their systems as a way of offering a complete package deal and enabling you to use your desktop right out of the box. These bundled packages vary from company to company and depend on the use for which the system is intended. Corporate desktops usually include desktop-management software that assists IT managers and administrators in monitoring the health and stability of PCs on their network. Depending on the size of your business, a suite of office applications, such as one of the Microsoft Office suites, may be bundled at no additional charge, as well as an antivirus program. Home desktops typically offer some combination of education, entertainment, and programs for editing audio and video as part of the deal. Software will add to the total cost of a desktop, so shop for the package that works for you.
The level of
after-sale support you'll receive will depend on where you buy your
system. Warranty periods and restrictions will differ from manufacturer
to manufacturer. Some warranties may not cover components such as mice,
monitors, and other peripherals. Even purchasing a contract for on-site
technical support doesn't guarantee that a service representative will
show up at your home or place of business. The manufacturer will
generally try to resolve any technical issues through other, cheaper
means, such as over the phone or via the Web, and you may find yourself
opening the system and installing replacement components. Free telephone
tech support may leave you spending a good amount of time wading through
phone menus and waiting for an available support agent. In some cases
you may have to box the system up and ship or carry it to a repair
depot. On the other hand, some vendors provide on-site technical support
for your system or on-site service at no extra charge. Read the fine
print before purchasing an extended warranty or on-site service
contract. |
|||
|
|
  |
|
||
|
Processors.
DRAM (dynamic random access memory).