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mean that a faster version of your old processor may no longer be available because that series of processor has been replaced by a later series.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 motherboard?a 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:

Decide which CPU to use

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.

Buy a motherboard that uses the right chipset

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 nVIDIA nForce2-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.

Make sure the motherboard supports the exact processor you plan to use

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 board with flexible host bus speeds

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 speeds?200, 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.

Make sure the board supports the type and amount of memory you need

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 current?i.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.

Avoid hybrid motherboards

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.

Check documentation, support, and updates

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 to?and perhaps even base their buying decisions on?the quality of the web site that supports the motherboard.

Buy a motherboard with the proper form factor

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:

Expansion slots

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 motherboards?those with embedded video, sound, and/or LAN?can 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.

Ports, connectors, and front-panel LEDs

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.

Embedded sound and video

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., nVIDIA), 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.

Power management and system management

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.

Wakeup functions

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.

Jumperless (or single-jumper) configuration

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.

Boot devices supported

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.

Minor or special-purpose features

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).