motherboards and their components
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Motherboards and Their Components
Motherboards and Their Components Motherboard (Main Board, System Board, Desktop Board) OverviewThe motherboard is the part of the computer to which every other component is connected. It contains the processor socket(s), memory slots, expansion card slots, ports for mouse, keyboard, printer, et cetera, and electronic parts, known as the chipset, to make everything run. Most motherboards contain some built-in components such as video, sound, network adapter, and others, and they therefore have ports for whatever built-in components they have. Form FactorsSince the first PC was introduced, several types of motherboards have been used; the types referred to as form factors. What differentiates form factors of motherboards is their size, arrangement of components on the boards, and other details. Cases and power supplies are also classified into the same form factors; they all have to match to some extent for the components to fit properly into the case. Form FactorsThe following form factors of motherboards are among those that have been used for PCs: AT (Baby AT) ATX (Advanced Technology eXtended)LPX (Low Profile eXtension)Micro ATXNLX (New Low Profile Extended)and Flex ATXMotherboard Components It is important for technicians to be able to identify the parts of any motherboard. Figure 3.1 shows an ATX motherboard.
Figure 3.1: ATX motherboard.Motherboard Components CPU slot/socket: We discuss CPUs in detail later in this chapter.Memory slots: Physical configurations of memory chips have changed over the years, but the industry seems to have settled on dual inline memory modules (DIMMs). These chips have 72 or more pins per side, Motherboard Components
Figure 3.2 shows DIMM slots. Motherboard Components BIOS chip: We discuss BIOS chips in greater detail later in this chapter.Chipset: Every motherboard has a number of integrated circuits (chips or ICs) permanently installed on different parts of the board. Each chip has a separate function. It is most common for these chips to all be from a single manufacturer. Motherboard Components AGP slot: All motherboards made in the last several years that don't have built-in video, and some that do, have an accelerated graphics port (AGP) slot. This is the slot for a video adapter. Figure 3.3 shows an AGP slot.
Figure 3.3: AGP video slot.Motherboard Components Expansion slots (ISA and PCI): Expansion devices in card form, such as modems and network adapters, go into these slots. Newer motherboards have only Peripheral Component Interconnect (PCI) slots, while some middle-aged boards have a combination of PCI and the older Industry Standard Architecture (ISA) slots. Motherboard Components
Figure 3.5: A combination ISA/PCI slot.Motherboard Components
Figure 3.6: ISA cards' pins are much bigger and farther apart than PCI cards' pins.Motherboard Components See the video "Removal and Replacement of Expansion Cards" for more information. The filename is Removal_and_Replacement_of_Expansion_Cards.mpg.
Motherboard Components Power connectors: Every motherboard has power connectors that look something like the one shown in Figure 3.7.
Figure 3.7: ATX power connector.Motherboard Components
Figure 3.8: If the motherboard has this 12-volt connector, it must be connected. The connector from the power supply is in the inset.Motherboard Components Note that an AT (form factor) motherboard power connector is different from an ATX connector. The AT connector has two parts, each with black wires on one end. They must be installed with the black wires next to each other at the center of the motherboard's connector, as shown in Figure 3.9.
Figure 3.9: AT power connector.Motherboard Components Battery: We discuss the motherboard battery later in this chapter. Disk drive connectors: Virtually every motherboard has two IDE connectors for up to four IDE devices, usually one or two hard drives and one or two optical (CD or DVD) drives. With the proper cables, each connector can support two drives. In addition, there is a connector for the floppy drive. Figure 3.10 shows IDE connectors.
Figure 3.10: IDE and floppy disk drive connectorsMotherboard Components Header connectors: These are multi-pin connectors that are similar to but smaller than the disk drive connectors for ports such as serial, parallel, USB, audio, case speaker, and so forth. Ports: Motherboards have some or all of the following ports: serial, parallel, game, PS/2 mouse, PS/2 or AT keyboard, and USB. Identifying a MotherboardWhile many motherboards are easily identifiable, a few aren't. Here are some identification methods: Look for the brand name, model number, and revision number printed on the circuit board.Look for a sticker underneath the lowest expansion slot. It might not be visible without disassembling the computer and removing the board, or at least by using a small mirror on a handle (preferably nonconductive).On boot-up, look on the first screenif the information does appear, you won't have long to see it unless you press the Scroll Lock key.The information might appear somewhere in the BIOS.If the computer is a brand-name computer, you can often find the board used by going to the computer manufacturer's Web site.
Selecting a Quality MotherboardWhile the chipset manufacturer can make a difference in the quality of a motherboard, the manufacturer of the board itself makes the most difference. To select the best, most appropriate board, first decide on the features the user needs such as type and number of expansion slots plus the needed built-in components. Also note that motherboards take only one type of memory. Generally, the faster the memory, the more expensive it is. Therefore, decide on the best memory you can afford and select the motherboard accordingly. Selecting a Quality MotherboardNext, evaluate the manufacturer based on its available technical support and its Web site. Then, consider warranty and cost.Another useful method is to go to the processor manufacturer's Web sites for recommendations of motherboards (intel.com, amd.com). Built-In (Onboard) ComponentsIt is easy to tell when a board has these systems built injust look for the appropriate connectors. If the computer is fully assembled, look at the back to determine the functions that are built in. The computer shown in Figure 3.11, for example, has built-in video and sound. This is apparent because these connectors are closer to the top of the computer. By the way, the shiny metal plate surrounding the ports for the built-in components is called the I/O shield. Built-In (Onboard) Components
Figure 3.11: A computer with built-in sound and video.Built-In (Onboard) ComponentsCertain instances call for replacement of a built-in component, usually when that component fails or when the user desires a better component or one with more features. It is practically impossible to replace the individual parts on the motherboard, so the answer is to add an expansion card with the desired function. Removal and Replacement of MotherboardsWhen would you need to replace a motherboard? There are a few situations when doing so makes sense; for example, when the board fails while under warranty, or the user wants to upgrade a good quality computer but the motherboard won't support a faster processor or more memory. Removal and Replacement of MotherboardsTip: Unless the new motherboard is identical to the old one, most or all drivers will be different. For this reason, you'll want to back up data on the hard drive containing Windows, if necessary, and format (erase) the hard drive before going any further. When you have installed a new board, be prepared to install Windows and all programs from scratch and to restore data from the backup. Removing the Existing MotherboardThis is a fairly simple matter. First, with the power off, disconnect every cable from the outside of the computer. After opening the case , make sure to use a grounding strap and perhaps other anti-static devices. Then, disconnect all cables you can access from inside the computer, including the disk drive cables and small audio cables. You will most probably have to remove the drive cage. Remove any remaining cables and all cards in expansion (PCI, ISA, AGP, etc.) slots and place them on an anti-static surface. It is probably best to leave the processor and memory in their places for now. Now, remove the screws holding the motherboard to the case, and carefully remove the board. If it is still usable and/or the CPU and memory is still in place, place it on the anti-static surface. Installing the New MotherboardFirst, make sure that the new motherboard is the same form factor as the case. Then, make absolutely certain that the power supply is set for the correct voltage to avoid zapping the new board. Next, make sure that no conductive surface comes in contact with any metal parts of the case. While some cases have elevated mounting holes that hold the board away from the case wall (see Figure 3.13), other cases call for standoffs. Standoffs are small spacers that go between the board's and the case's mounting holes (see Figure 3.14).
Installing the New Motherboard
Figure 3.13: Elevated mounting holes.
Figure 3.14: Standoff assortment.Installing the New MotherboardAfter screwing in the screws, you need to install the power connectors and then follow the manufacturer's instructions for setup, which we discuss next. After you've done this, reinstall all of the compatible peripheral devices (if any) that were connected to the old motherboard. Diagnosing Motherboard ProblemsThe most obvious sign of a damaged motherboard is a burnt or otherwise visibly damaged part.
Naturally, motherboards can die without any visual signs. If you are sure the power supply works and