PC Hardware in a Nutshell, 3rd Edition [Electronic resources] نسخه متنی

3.2 Choosing a Motherboard

You
can sometimes upgrade a system cost effectively without replacing the
motherboard. The more recent the system, the more likely this is to
be true. The easiest upgrade is always replacing a processor with a
faster version of the same processor. Doing that may simply mean
pulling the old processor and replacing it with the faster one,
although a BIOS upgrade may also be needed. Alas, there is no
guarantee that a given motherboard will support a faster version of
the same processor, or that a required BIOS upgrade will be
available, and the rapid advances in processors mean that a faster
version of your old processor may no longer be available because that
series of processor has been replaced by a later series.

The next-easiest upgrade is to replace the processor with a later
model from the same generation. For example, you may be able to
replace a Pentium II/350 with a Pentium III/850 or, by using a
slocket adapter, with a cheap, fast Celeron. When upgrading to a
later-model processor, a BIOS upgrade will almost always be needed,
and you should check the motherboard manufacturer's
web site carefully to determine which configurations are supported.

Faster processors may draw more current, and the VRMs on an older motherboard may be inadequate to support the new processor. Even if the processor appears to work properly at first, running it for long may damage both the motherboard and the processor. Always check to make sure that the exact processor you plan to install is supported by the motherboard.

It doesn't make sense to
stretch an old motherboard too far. Just because you

can upgrade a system without replacing the
motherboard doesn't mean that you

should do so. Motherboards are inexpensive,
typically $75 to $150. Doing an in-place upgrade instead of replacing
the motherboard leaves you with the limitations of the old
motherboard and may limit the performance of the new processor.
Before you decide to keep the motherboard, find out the costs and
benefits of replacing it instead. Don't forget to
factor in the supplementary benefits of a new motherboarda
better chipset and BIOS, support for the latest hard disk standards,
etc. You may well decide it's worth spending the
money to replace the motherboard. In fact, you may decide simply to
retire the existing system to less-demanding uses and build a new
system.

Use the following guidelines when choosing a
motherboard:

The CPU you choose determines the type of
motherboard you need. Choose a Socket 478 Pentium 4 or a Socket A
Athlon motherboard. With fast Socket 478 and Socket A processors
available at very low prices, there is no point in buying into older
technology, even though motherboards and processors using that
technology may remain available.

For a single Pentium 4
or Celeron processor, choose a motherboard that uses an Intel 845-,
865-, or 875-series chipset, depending on your budget and priorities.
For a single Athlon processor, choose a motherboard that uses an

n VIDIA

n Force2-series
chipset. For a dual-processor Athlon MP system, choose a motherboard
that uses the AMD 760-MPX chipset. We have not tested any dual-Xeon
systems, and so cannot make specific recommendations for them.

Just because a motherboard claims
that it supports a particular processor doesn't mean
that it supports all members of that processor family. For example,
some motherboards support the Pentium 4 processor, but only slower
models. Other motherboards support fast Pentium 4s, but not slower
Pentium 4s or Celerons. Similarly, many motherboards support the
Athlon with a 200 or 266 MHz FSB, but not Athlon models that use a
333 MHz or 400 MHz FSB. Make sure the motherboard supports the exact
processor you plan to use, before you buy it.

Choose
a motherboard that supports at least the settings you need now and
expect to need for the life of the board. For example, even if you
install a 400 MHz FSB Celeron initially, you should choose a
motherboard that supports Pentium 4 processors using the 400, 533,
and 800 MHz FSB speeds. Similarly, even if you plan to install an
inexpensive 266 MHz Athlon at first, you should choose a motherboard
that supports the full range of Athlon FSB speeds200, 266,
333, and 400 MHz. Boards that offer a full range of hostbus speeds,
ideally in small increments, give you the most flexibility. If you
intend to overclock your system, make sure the motherboard offers
multiple choices of hostbus speed (again, the smaller the increments,
the better) and allows you to set CPU voltage, ideally over a wide
range in 0.05-volt increments.

Any new motherboard you
buy should use DDR-SDRAM. PC2100 memory is still sold new, although
it is now used only in the least-expensive systems. PC2700 memory is
mainstream, and likely to remain so until DDR-II memory becomes
widely available. PC3200 memory, which as late as early 2003 we
expected to remain a technical curiosity, was legitimized by the
Intel 865- and 875-series chipsets, but PC3200 memory remains
difficult and expensive to produce relative to PC2700 memory, and is
therefore likely to be used only in systems for which memory
performance is a high priority. Even so, we recommend choosing a
motherboard that supports at least PC2700 and PC3200 memory.

Do not make assumptions about how much memory a motherboard supports.
A motherboard has a certain number of memory slots and the literature
may state that it accepts memory modules up to a specific size, but
that doesn't mean you can necessarily install the
largest supported module in all of the memory slots. For example, a
motherboard may have four memory slots and accept 512 MB DIMMs, but
you may find that you can use all four slots only if you install 256
MB DIMMs. Memory speed may also come into play. For example, a
particular motherboard may support three or four rows of PC2700
memory, but only one or two rows of PC3200 memory.

Also, chipsets and motherboards vary in terms of how much memory of
different types they support. For example, the Intel 845 chipset
supports up to 3 GB of SDR-SDRAM, but only up to 2 GB of DDR-SDRAM.
Registered versus unbuffered memory may also be an issue. For
example, although Tyan recommends (and we concur) that you use only
Registered DDR-SDRAM with its S2460 Tiger MP dual-Athlon board, some
have reported that the Tiger MP does work properly with unbuffered
memory, but only if you limit it to one DIMM.

Nor do all motherboards necessarily support the full amount of memory
that the chipset itself supports, even if there are sufficient memory
sockets to do so. Always check to determine exactly what combinations
of memory sizes, types, and speeds are supported by a particular
motherboard.

For a general-purpose system, support for 512 MB of RAM is
acceptable, and 1 GB is better. For a system that will be used for
memory-intensive tasks such as professional graphics, make sure the
motherboard supports at least 1 GB of RAM, and 2 GB or more is
better.

Although you may be able to find a new motherboard that supports migrating existing memory from the old motherboard, it's usually not a good idea to do so unless that older memory is currenti.e., PC2700 DDR-SDRAM or better. Memory is cheap, and it seldom makes sense to base a new motherboard purchase decision on the ability to salvage a relatively small amount of old, slow memory.

Every time there's a
change in memory technology, some manufacturers make motherboards
that accept both the old and new types of memory. During the
transition from SDR to DDR memory, such hybrid motherboards were
common. We expect to see hybrid DDR/DDR-II motherboards when DDR-II
memory begins shipping in volume. We think buying a hybrid
motherboard is usually a mistake, both because we've
yet to see one that worked well with both types of memory, and
because hybrid motherboards are often problematic in other respects
as well. Motherboards are relatively inexpensive. If you want to use
DDR-SDRAM, buy a DDR-SDRAM motherboard. In a couple of years, when
DDR-II memory becomes available, if you want to use DDR-II memory,
buy a native DDR-II motherboard. The advantages of new memory
technologies are seldom compelling enough to make it worthwhile to
compromise on a hybrid. Wait until second-generation motherboards are
available for the new memory technology.

Before you choose
a brand or model of motherboard, check the documentation and support
available for it, as well as the available BIOS and driver updates.
Some people think that a motherboard that has many available patches
and updates must be a bad motherboard. Not so. Frequent patch and
update releases indicate that the manufacturer takes support
seriously. We recommend to friends and clients that they give great
weight toand perhaps even base their buying decisions
onthe quality of the web site that supports the motherboard.

If
you are building a new system, choose an ATX motherboard that best
meets your needs, and then buy an ATX case and power supply to hold
it. For most purposes, a full-size ATX motherboard is the best
choice. If system size is a major consideration, a micro-ATX or
FlexATX motherboard may be a better choice, although using the
smaller form factor has several drawbacks, notably giving up one or
two expansion slots and making it more difficult to route cables and
cool the system.

The preceding issues are always important in choosing a motherboard.
But there are many other motherboard characteristics to keep in mind.
Each of them may be critical for some users and of little concern to
others. These characteristics include:

Any motherboard you buy will provide some
PCI expansion slots, but motherboards differ in how many slots they
provide. Three PCI slots is marginal, four adequate, and five or more
preferable. Integrated motherboardsthose with embedded video,
sound, and/or LANcan get by with fewer PCI slots. Using ISA
slots should be avoided at all costs, so the number of ISA slots is
largely immaterial. Having an AGP 2.0 or 3.0 slot (4X or 8X) is a
definite plus, even if the motherboard includes embedded video. Many
recent motherboards include an Audio-Modem Riser
(AMR) slot or Communications and
Networking Riser (CNR) slot, the sole
purpose of which is to allow system manufacturers to embed low-end
audio and communications functions cheaply. Very few AMR and CNR
components are commercially available, so the presence or absence of
an AMR or CNR slot is immaterial, except in that the space occupied
by an AMR or CNR slot is much better used to provide another PCI
slot.

It may seem strange to put
something generally regarded as so important in a secondary category,
but the truth is that warranty should not be a major issue for most
users. Motherboards generally work or they don't. If
a motherboard is going to fail, it will likely do so right out of the
box or within a few days of use. In practical terms, the
vendor's return policy is likely to be more
important than the manufacturer's warranty policy.
Look for a vendor who replaces DOA motherboards quickly, preferably
by cross-shipping the replacement.

At a minimum, any new motherboard should
provide four or more USB 2.0 ports and a dual ATA/100 or faster hard
disk interface. Ideally, the motherboard should also provide at least
two Serial ATA connectors, and four is better. (Some motherboards
that provide four S-ATA connectors include only a single parallel ATA
interface, which is acceptable.) Given our druthers,
we'd also like to see a serial port, an EPP/ECP
parallel port, a PS/2 keyboard port, a PS/2 mouse port, and an FDD
interface, but those "legacy" ports
are fast disappearing.

So-called "legacy-reduced"
motherboards lack serial, parallel, keyboard, mouse, and FDD ports.
We avoid using those when possible because there are simply too many
times when "legacy" ports are
useful, but as time goes by it will be increasingly hard to avoid
legacy-reduced motherboards because they'll
eventually all be that way. We can live with the lack of parallel
ports, because most printers nowadays use USB. Similarly,
it's easy enough to use a USB keyboard and mouse if
the motherboard lacks PS/2 connectors. Even serial ports are no
longer critical, now that most modems and PDA cradles use USB. But we
really, really resent the loss of the humble floppy drive controller.
There have been times when the lack of a floppy drive controller cost
us literally hours of extra work because we needed to transfer one
small file or boot a system from a floppy disk, and had no way to do
so. Oh, well. We guess we'll just have to get used
to it.

Check the documentation to determine how the header pins for
front-panel switches and indicators are arranged on the new
motherboard. It's quite common to find that existing
cables aren't long enough to reach the connectors on
the new motherboard, or that the new motherboard uses different pin
arrangements for particular connectors.

Some motherboards include embedded sound,
video, and/or LAN adapters as standard or optional equipment. In the
past, such motherboards were often designed for low-end systems, and
used inexpensive and relatively incapable sound and video components.
But nowadays many motherboards include "name
brand" sound (e.g., SoundBlaster PCI), video (e.g.,

n VIDIA), and LAN (e.g., Intel or 3Com) adapters,
making them good choices around which to build a mainstream midrange
system. Such motherboards normally cost from $0 to $25 or so more
than similar motherboards without the embedded peripherals, allowing
you to save $50 to $150 by buying the integrated motherboard rather
than separate components. If you buy such a motherboard, make sure
that the embedded devices can be disabled if you later want to
replace the embedded adapters with better components.

Embedded adapters often use the main CPU, which can reduce performance by a few percent. The speed of current processors means this is seldom an issue. However, if processor performance is critical, you may wish to use a motherboard that has few or no embedded functions.

We regard power management as a
useless feature and do not use it. It saves little power, increases
the wear and tear on the equipment due to frequent power cycling, and
tends to cause bizarre incompatibilities. We have experienced
numerous problems with ACPI, with many different motherboards and
operating systems, including systems that go into a coma rather than
going to sleep, requiring a hard reboot to recover, and so recommend
not using it at all. If for some reason you need power management,
make sure the motherboard you buy supports at least a subset of the
ACPI specification. Most current motherboards support some ACPI
functions, but determining exactly which requires detailed
examination of the technical documents for that motherboard.

System management is usually unimportant outside a corporate
environment. If system management is an issue for you, look for a
motherboard that supports all or some of the following features:
voltage monitoring, CPU and/or system temperature sensors, chassis
intrusion alarm, and fan activity monitoring for one or more fans.

Again, these features are primarily
of interest to corporate IS folks rather than individual users. But
if wakeup functions are important to you, you can buy a motherboard
that supports "wake-on" on some or
all of the following: LAN activity; modem ring-in; keyboard/mouse
activity; and real-time clock.

Older-style motherboards are
configured mostly by setting jumpers. Recent motherboards use fewer
(or no) jumpers, depending instead on CMOS Setup to configure
motherboard settings. A board that uses CMOS Setup is marginally
easier to configure than one that uses jumpers.

Any motherboard supports booting
from the hard drive or a floppy drive. Most motherboards also support
booting from El Torito-compliant CD-ROM drives and from
floppy-replacement drives such as the LS-120 or Zip drive. Some
motherboards support booting from the network. If boot support is an
issue for you, make sure the motherboard you buy supports booting
from your preferred device. Also make sure that CMOS Setup allows you
to specify a boot sequence that allows you to make your preferred
device the primary boot device.

Motherboards attempt to differentiate themselves by including various
minor features, such as an IRDA port or additional fan power headers
(at least one is needed for the CPU fan, but some motherboards
include two or three power headers to support supplemental fans).