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[ The PC Guide | The PC Buyer's Guide | Designing and Specifying PC Systems and Components | Detailed Considerations and Tips for Specifying Particular Components ]

Motherboards

Description: The motherboard (also sometimes called the mainboard or system board) is the central circuit board of the PC, and in most respects, the heart of any computer. It contains several important core components, including the chipset, which controls many of the most essential functions of the PC. It directly interfaces with other key components of the PC, and is responsible in large part for the stability, feature support, expandability and upgradeability of any system.

Motherboards are complex, and include many different integrated devices, which makes it difficult to describe in simple terms how to buy one. As a result, this section is rather long. Unfortunately, if you want to get the motherboard that is best for you, you need to consider a lot of different issues. In fact, I haven't even listed all the different specific parts and minor selection issues involved in motherboard selection, or this page would be even longer! You do have to do your research if you have a specific need, especially if you are looking to build or have someone build to order something like a server. (For regular PCs the detail provided here should be more than adequate.)

Tip: For a great deal of additional information on the motherboard and its components, including more discussion of many of the technical details, criteria and features mentioned below, see the Reference Guide section on the motherboard and system devices.

Role and Subsystems: The motherboard is a central part of the system processing core, and directly interacts with every subsystem in the PC. The CPU and memory plug into it directly, the video does as well (and may even be integrated on it), and all peripherals attach to it in way or another. You could pretty much say that the motherboard "has its fingers in everyone's pie". :^)

Expansion and upgrading particularly key off the system's motherboard selection. This is because support on the part of the motherboard is required for the use of just about any hardware. You can only add a new CPU, or expand your system memory, or add a new video card if your motherboard will be compatible with the new hardware. Therefore, if you care about upgrading, choose wisely. At the same time, remember that it is common for new hardware, especially CPU and memory technology, to require a new motherboard due to changes in slot or socket design.

Related Components: The motherboard is most closely related to the CPU, system memory and video card. The CPU and memory are normally specified at the same time as the motherboard; the video card may be as well, but sometimes just the interface for the video card is chosen as the motherboard is selected. The system case and power supply are also related to the motherboard by virtue of the need to match their form factors, and are also specified at the same time.

Key Compatibility Selection Criteria: There are a large number of different criteria by which motherboards are selected. In some cases a specific need of the system will dictate the choice of motherboard, but usually the choices are "narrowed down" by considering the following key issues:

  • Form Factor: The initial decision is the form factor of the motherboard, which must be mated to that of the power supply and case. There are three sub-issues here. First, the physical size of the board must be compatible with the system case. Second, the motherboard must have compatible power supply sockets to match the connector or connectors coming from the power supply. Third, the system case must have the right type of power switch for the motherboard.
    The two most common general form factor families are AT and ATX, but each has a number of variants. AT has "Baby AT", and ATX has "mini ATX", microATX, FlexATX and others. And even within a particular form factor type there are slight variations in size between specific models. Be sure, especially if you are doing an upgrade or using a small case, that the particular board you are selecting will fit.
    The connection from the power supply to the motherboard is different for older form factors (AT, Baby AT, LPX, etc) than it is for newer ones: make sure the board is compatible. Some boards support either connector type, making this issue easier. Newer ATX family boards also use soft power, where the power switch on the case connects to the motherboard, not the power supply, so you don't want to try to put an ATX-only motherboard into a system with an AT case and power supply.
  • Chipset: The chipset is the core logic of the motherboard and is responsible for most of its characteristics. After form factor, this is a primary differentiator of different motherboards, as the chipset is key to what CPUs, memory types, and other peripherals the motherboard will support. Intel is a prime designer and maker of chipsets, normally supporting its own CPUs of course; for non-Intel CPUs you will be looking at non-Intel chipsets. At one time Intel chipsets utterly dominated the market, but the situation is more balanced now, with a number of other manufacturers such as Via and ALi taking increasing market share of both OEM systems and retail motherboard sales.
  • CPU Support: The chipset must support the particular CPU you want to use, or allow you a choice you will be happy with. CPU support is a function of the chipset choice, the bus speed and multiplier settings provided on the board, the voltage levels provided on the board, and also compatibility from the system BIOS. Support for additional CPUs sometimes comes from BIOS upgrades. CPU support may be specified by listing particular CPUs, or by specifying the CPU interface (slot or socket type) that the motherboard implements.
    Note that in some cases there are compatibility lists for particular platforms, especially for non-Intel CPUs. These are lists of specific boards that have been tested and approved for use with the CPU in question. It's a good idea to try to get a board on the list if it is applicable. Check the CPU maker's web site for assistance.
  • Video Support: The video card either goes into a slot on the motherboard, or its functionality is integrated onto it. Most modern systems use AGP video, so you will want to look for an AGP slot on the board. There are different levels of AGP support: newer boards will support faster modes such as 4X AGP and AGP Pro, as well as older cards. If you are upgrading and using an older PCI video card then plan on using a PCI slot for it (I am not even going to mention ISA video--scary! :^) ).
  • Memory Support: Motherboards vary in terms of the number of memory slots they provide, and also what sizes and types of modules are supported. While today this is fairly universal between brands, check carefully, especially if you want to run a lot of memory (256 MiB or more). Note that motherboards also vary in terms of the speed of the memory bus, but this is tied to some extent to the choice of CPU and chipset.
  • System Bus Types And Number: Motherboards differ greatly in terms of the number of system bus slots they support. This is often a function of board size: smaller boards usually have fewer slots. If you are planning a system that will have many expansion devices, be sure the motherboard has enough of the right types of slots. If you are upgrading, pay special attention, especially if you need ISA slots, as they are becoming harder to find today.

Note: A common design is to share two slots of different types; you can use one or the other of that set. If you see a specification such as "1 AGP, 4 PCI, 2 ISA (1 shared)", this means that one PCI and one ISA slot are right next to each other; only one of that pair can be used. So this board can use 1 AGP slot (for the video card), and either 4 PCI and 1 ISA, or 3 PCI and 2 ISA. (Sometimes one PCI and one ISA are shared and they don't mention this--assume it unless you can verify otherwise.)

Performance and Capacity Selection Criteria: There are a few issues that most motherboard buyers look for in terms of their impact on overall system performance and capacity issues. Mostly, performance of the system isn't a function of the motherboard but the other hardware it supports and works with (see the discussion of performance impact further down). You may want to look for these when shopping, however:

  • IDE/ATA Controller: The interface controller for the hard disk and other IDE/ATA compatible drives is built into the chipset on most boards. Some have support for higher interface transfer speeds. See the discussion of hard drives for more on this.
  • RAID: Some newer motherboards are now coming with support for software RAID on their integrated disk controllers. While certainly not high on the list of performance RAID implementations, this may be of appeal to some.
  • Multiple CPU Support: Some motherboards support the use of multiple processors (when used with capable CPUs and suitable operating systems and application software).
  • Memory Capacity: The number of slots provided on the board and how much each can hold limits total usable memory and expandability, and memory is certainly very important to performance, especially on high-end systems.
  • I/O Interfaces: Almost all modern motherboards come with support for at least the following: two serial ports, one parallel port, one keyboard port, and one PS/2 mouse port. Most also now come with two USB ports, which are close to being essential in today's peripheral market. Some come with other interfaces such as a game port for a joystick or other game controller.
  • Overclockability: If you plan to overclock your system, you'll want to pay attention to reviews that assess different motherboards in terms of how much they facilitate system overclocking.
  • System Cache Type And Amount: Most modern PCs now have their secondary cache integrated into the physical processor package, but older designs (primarily for the 486, original Pentium, and compatible non-Intel CPUs) use cache on the motherboard. The amount of cache has an impact on overall performance, though it isn't enormous.

Quality Selection Criteria: As a key system component, the quality of the motherboard is very important, and often overlooked. As someone who recently spent weeks diagnosing a flaky system that turned out to be a result of a bad motherboard, let me assure you that motherboard quality is essential. :^) Note that some manufacturers, and some models, have generally better reputations for quality and stability than others. Of course you're not going to be able to find this out by asking the manufacturers. :^) Rely on advice from those you trust and a general sense of who has success with what makers based on your research. When assessing quality, look at the following factors:

  • Stability and Reliability: For my money, this is the most important characteristic of any motherboard: reliable, stable operation. You will need to research others' experiences to judge this, and also assess the past history of the company.
  • Layout: Motherboards vary greatly in terms of how the various components are laid out. Better layouts space components to prevent crowding or interference, and make it easier to build the system. Look for comments from those who have installed a board in the past: did they have a difficult time? In general, bigger boards are better than smaller ones in this regard. Look especially for support components crowded around the CPU slot or socket that might interfere with CPU heat sinks or fans.
  • Rigidity and Construction: Better boards are thicker and stronger than cheap ones.
  • Accessory Set: Be sure that the motherboard includes a full set of needed accessories, such as floppy and IDE/ATA cables, driver disks, retention module for the CPU (if appropriate) and so on. (These are usually included in retail-packaged boards; see below).
  • Manual and Online Documentation: The motherboard manual is an essential aid in setting up your system; assess its quality, as well as the quality of supplemental documentation such as that provided by the manufacturer's web site.
  • ECC Memory Support: For the best reliability and stability, look for a motherboard that works with ECC memory. This requires both chipset and specific motherboard support, as well as special memory modules.
  • BIOS Upgrade Support: BIOS upgrades are key to future support for new technologies, as well as correcting known problems with the board. Virtually all motherboards today have a user-upgradeable flash BIOS. Look for a manufacturer that has a history of supporting older products.
  • User-Replaceable CMOS Battery: The CMOS battery holds your BIOS settings when the PC is turned off. Some motherboards use a button battery or other replaceable discrete component, but others integrate the battery into the board. The battery is not a major component, but without it your system would need to be reconfigured every time it is turned on, which most users would consider unacceptable. As such, a board with an integrated battery at best can be considered "eventually disposable"; after a few years the battery will fail and cannot be replaced.
  • Ability To Disable Integrated Peripherals: Integrated peripherals can reduce system cost, and may be acceptable for some applications, but be sure they can be disabled through either a hardware jumper or BIOS setting. Also watch out for boards with integrated AGP video and no AGP slot: this saves the board maker a buck or two but makes it impossible for you to ever upgrade the video on the system (well, maybe you can add a PCI video card, but that's not what you really want in most cases.)

Important Features: Here are a few other optional features sometimes found on motherboards:

  • Integrated Components: Some motherboards come equipped with integrated sound, networking or SCSI host adapters. These can give you capabilities at a reduced cost compared to discrete components, but may also cause complications, and may not be the best of quality. See here for more.
  • Monitoring: Many motherboards now offer sensors and BIOS code to monitor various temperatures and other conditions within the system, to improve reliability.
  • "Jumperless" Setup: Some boards have replaced traditional hardware jumpers for configuring them, with BIOS settings. These are called "soft" or "jumperless" boards (even though they usually do contain some jumpers). If you tinker with your system a great deal or overclock this can be a very useful feature, but if like most people you are going to just set up the system once and then leave it alone, it's of little value in this author's opinion.
  • Boot Block or Dual BIOS: Some better motherboards incorporate a security feature such as these that will let you recover from a failed BIOS upgrade or virus that wipes out the system BIOS program.

"Magic Numbers" To Watch For: Despite its complexity--or perhaps because of it?--motherboards are relatively free of magic numbers. There are just too many issues to take into account to even try to boil matters down to one or two numbers. Another issue is likely that motherboards are not commonly marketed directly to the general buying public.

Performance Impact: The motherboard is a bit of a paradox when it comes to performance: it is vitally important to the overall performance of the system, but generally is not a major contributor to performance itself. What I mean is this: the motherboard determines what other components you will use in your system, and thus is the key to the overall performance of the system. But the motherboard itself doesn't impact performance greatly.

Traditionally, there has been a lot of "benchmark bogosity" around when it comes to motherboards. Most web sites and magazines that reviewed motherboards over the years would benchmark different motherboards that used the same chipset and CPU, and then highlight what were usually small differences in benchmark scores. These discrepancies were usually not significant, and in fact were often arguably within the margin of error of the benchmark program! Fortunately, many of the better review sites are now recognizing that most motherboards benchmark within a few percentage points of each other, and are explicitly noting that such differences are not very important.

The bottom line is this: for performance issues, pay attention to the chipset on the board, and the CPU and memory you are going to use in it. Choose from different motherboards in the same platform on the basis of quality and features, not benchmark scores.

Retail, OEM and Gray Market Issues: Motherboards are usually sold as retail boxed items, but are sometimes found as OEM or gray market components. It is strongly advised that you buy a full retail product, even if it costs $10 or so more, as this will ensure that you get all the support components you will probably need to build or upgrade a system, and will also simplify warranty issues.

Importance of Manufacturer: I consider it mandatory to buy a motherboard from a reputable, well-known manufacturer: there are around a dozen big-name manufacturers, most of them based in Taiwan. Buying a cheap generic motherboard is a very bad idea. This is not only because of the dubious quality of some generic boards, but also because in the event that you ever need support, assistance or a BIOS update in the future from a "no-name" manufacturer, you will likely be stuck. Take my advice and "just don't do it". If you can't positively identify the manufacturer of the board, or if it's a manufacturer about whom you can find no information, get something else.

Note that most of the boards made by the big companies are pretty good, but occasionally there are some problems with particular models. Research the specifics before making a decision, and don't assume a company is bad based solely on a couple of bad reports.

Typical Component Lifetime: Motherboards last for the life of the PC. ;^) I'm being cute, but the fact is that the motherboard is the central component in the PC. It is solid state and not likely to ever fail, but may over time become obsolete; still, replacing it really means replacing much of the "guts" of the PC, due to the interconnections between components that I have mentioned above.

There was a time when you could plan for the future and have a good chance of being able to use a future CPU with the motherboard you were purchasing today. Unfortunately, this is not nearly as easy to do today as it was in years past. The sockets and slots used to interface processors to motherboards change too rapidly, and other technologies seem to evolve quickly as well. You may well be able to put a faster CPU of the same type into your system later on, but the next generation of CPU may well require a new motherboard.

Warranty Issues: Manufacturer warranties on motherboards typically range from one year to three years. You must be careful about how this warranty period is calculated, and the manufacturer's policies as well. In some cases the manufacturer only provides warranty support to the distributor or vendor, and will refuse to deal directly with the public--even for retail-packaged boards! The warranty period may begin when the manufacturer sold the board to the distributor, also. Be sure you are dealing with a good vendor that will support you properly.

Driver Support Issues: Some motherboards require drivers for Windows, especially ones that use non-Intel chipsets. Driver support is provided in part by the chipset manufacturer and in part by the motherboard manufacturer. Support is essential, but as long as you stick with a known brand, problems are atypical. Motherboards built around non-Intel chipsets are more likely to require special drivers than Intel ones, because Microsoft usually has support for Intel chipsets built into their operating systems (and for some non-Intel chipsets as well). Any motherboard may require drivers for some of its special components or features.

Special Specification Considerations: I've covered most of the issues in the discussions of compatibility, performance and quality criteria. I would add that it is prudent to avoid the first generation of any motherboard type, to stay away from possible problems that frequently crop up with new technology. This is especially the case when dealing with a new chipset, CPU or memory technology. Let others be unpaid beta testers.

Next: System Processors (CPUs)


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