MOTHERBOARD (MAIN BOARD, SYSTEM BOARD, DESKTOP BOARD) OVERVIEW
The 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.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. For example, if a motherboard has built-in sound, it will have built-in audio connectors as well.
It is important for technicians to be able to identify the parts of any motherboard.
While there are wide differences among the various brands and form factors, all motherboards have certain components in common:
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, although the two sides are so close to each other that it is not readily apparent that there are two sets of pins. Memory slots can accept one type of memory chip. Board design.further limits the compatible memory chips
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. You might see ASUS® brand motherboards, for example, with chipsets from Intel® or VIA. Some companies such as Intel make their own motherboards in addition to chipsets for competitors’ products. Manufacturers such as these virtually always use their own chipsets in their motherboards.
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.shows an AGP slot.
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. Some boards have expansion slots that give a choice between the two, as shown in. In this case, ISA cards have to be inserted upside down (with the soldered-on components facing the bottom of the computer) as compared to PCI cards.PCI slot and card standards are constantly being reviewed and updated. Several new versions of PCI slots are out or coming out soon. Low Profile PCI devices, for example, are designed to fit in newer small computers. The first iterations of these cards will fit in the original PCI slots, but future versions might not. Another new version is the Mini-PCI standard for devices such as network adapters and modems in laptops and other small computer-type devices. Also changing is the cards’ operating voltage. Newer devices are running at 3.3 volts rather than the older standard 5 volts. Moreover, 64-bit computers are available, although very expensive as of this writing, and there are necessarily 64-bit PCI cards to fit them.
Power connectors: Every motherboard has power connectors that look something like the one shown in Figure. Those of you who have taken A+ courses might know this as P-8 and P-9, although the actual designations vary from board to board. Some newer boards have a 12-volt
connector like the one in figure. The one in figure must be connected to the proper connector on the power supply for the motherboard to receive power. If the board has a 12-volt connector, it must be connected to the power supply to avoid damage to the board.
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.
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. Many new boards are coming with connectors for SATA drives as well. In addition, there is a connector for the floppy drive.
Ports: Motherboards have some or all of the following ports: serial, parallel, game, PS/2 mouse, PS/2 or AT keyboard, and USB. We discuss these later in this chapter.
How to Identify motherboad.
While many motherboards are easily identifiable, a few aren’t. Here are some identification methods:
1. Look for the brand name, model number, and revision number printed on the circuit board
2.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).
3.On bootup, look on the first screen—if the information does appear, you won’t have long to see it unless you press the Scroll Lock key.
4.The information might appear somewhere in the BIOS.
5.If the computer is a brand-name computer, you can often find the board used by going to the computer manufacturer’s Web site.
Just about all motherboards these days have some built-in components that were available only on expansion cards on earlier PCs. The most common of these are video, sound, network adapters, and modems. It is easy to tell when a board has these systems built in—just 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, for example, has built-in video and sound. This is apparent because these connectors are closer to the top of the computer. Other connectors are lower down, in the stack of expansion cards. By the way, the shiny metal plate surrounding the ports for the built-in components is called the I/O shield.