The motherboard is the PC's center of activity. All devices in a computer are in some way connected to the motherboard. It hosts the largest single collection of chips of any PC component and serves as the "street system" for the grid of wires that link all the components, making it possible for them to communicate.
After this lesson, you will be able to
- Identify a motherboard and its functions
- Locate and define the components of a motherboard
- Safely remove and replace a motherboard
The motherboard (one is shown in Figure 6.1) defines the computer's limits of speed, memory, and expandability. A computer needs more than just a CPU and memory. To accept input from the user, it needs devices, such as a keyboard and a mouse. It also needs output devices, such as monitors and sound cards, to cope with the powerful graphics and sound capabilities of the programs available today. A computer also needs "permanent" storage devices, such as floppy disk drives and hard disk drives, to store data when it is turned off. It is the function of the motherboard to provide the connectivity for all these devices, as well as for the CPU, RAM, and support integrated circuits (ICs).
The motherboard is usually the largest circuit board found inside the computer case. Motherboards come in a variety of shapes. One size does not fit all, and careful attention to size and location of mounting holes is required before installing a new motherboard in an older computer. A motherboard needs to fit in the space allotted for it, be secure in its mounts, be properly grounded, receive sufficient ventilation (for cooling of the CPU and other heat-sensitive components), and must not conflict with other hardware. When considering the purchase of a new motherboard (see Lesson 2 of Chapter 4, "The Central Processing Unit"), keep these things in mind:
- Most "generic" motherboards will fit into "generic" computers. One reason some people consider purchasing a PC clone is that it is easier to upgrade. Keep in mind that a hybrid PC (assembled by a small vendor, made from untested components) may be constructed of parts that may or may not be totally compatible. There may also be questions about EMI due to interaction between components or the way the parts set in the case.
- There are two major categories of motherboards: AT and ATX. The main difference between them is the type of power supply and main power switch each requires. When you order a new motherboard, be sure to first verify that it is compatible with the case and power supply to be used.
- If you are working on a brand-name computer, you might be required to purchase a new motherboard or other custom components from the same manufacturer.
- Before buying a motherboard, check its technical references to be sure that the new board will fit and will be compatible with any of the RAM and expansion cards the owner intends to use. Often, this information can be found in the owner's manual. If not, check the manufacturer's Web site, if one is available, or check other online resources such as technical libraries. A Web search using the keyword "motherboard" will yield sites dedicated to computer hardware.
- For all practical purposes, you cannot repair motherboards. They should be replaced if physically or electrically damaged. Your customer will get new technology, usually for a price lower than the cost of the repair.
- Because it is often the most difficult part of a system to replace (you have to remove all the equipment that is connected to it), check all other internal and external components before removing or replacing the motherboard.
- When obtaining a replacement, be sure to factor in the cost of all critical options found on the existing motherboard. Some have a built-in SCSI (Small Computer System Interface) Host Adapter or display adapters that might not be common. In that case, either make sure the new board offers the same level of support or install the appropriate add-on card(s) to bring the system up to the existing level of operation.
A motherboard comes with a variety of support chips soldered in place. The primary elements constitute the chip set and are designed to work with the CPU. These chips are highly complex and coordinated ICs that help the CPU manage and control the computer's system. When replacing a CPU, you must make sure that it is compatible with the chip set and supported by the motherboard. If not, the computer won't work. A basic chip set (see Figure 6.2) consists of a
- Bus controller
- Memory controller
- Data and address buffer
- Peripheral controller
On modern motherboards, you will find specialized chips to control things such as cache memory and high-speed buses. You will also find boards with fewer individual chips because the manufacturer has incorporated several functions into one chip.
Keep in mind that there is a wide range of features (with attendant cost increases for extras) available when selecting a motherboard. You will need to keep up to date on the types of processors, memory design, CPUs, and expansion slots available to recommend and obtain the right product for your customers.
Be careful in choosing motherboards with components like display adapters and sound cards on board. These are components that may not have all the features of their expansion card versions, and customers may decide to upgrade, leaving them with motherboard-based elements that could cause conflicts.
The following points summarize the main elements of this lesson:
- Motherboards come in many sizes and shapes, but generic boards are available that fit most clone computers.
- The motherboard determines the limits of the computer's capabilities.
- Chip sets are unique to each motherboard design and work with the CPU to manage and control the computer's system.
- You should make sure any new motherboard is compatible with the CPU, RAM, and any other critical hardware and features that are already installed on the computer.
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