Expansion Board NICsIf you have worked with PCs or studied for CompTIA’sA+ exam, you are probably familiar with the concept of a bus. A computer’s busis thecircuit, or signaling pathway, used by the motherboard to transmit data to the computer’scomponents, including its memory, processor, hard disk, and NIC. (A computer’s bus mayalso be called itssystem bus ormain bus.) Buses differ according to their capacity. Thecapacity of a bus is defined principally by the width of its data path (expressed in bits) andits clock speed (expressed in MHz). A data path size equals the number of bits that it cantransmit in parallel at any given time. In the earliest PCs, buses had an 8-bit data path.Later, manufacturers expanded buses to handle 16 bits of data, then 32 bits. Most newdesktop computers use buses capable of exchanging 64 bits of data, and some are evencapable of 128 bits. As the number of bits of data that a bus can handle increases, so toodoes the speed of the devices attached to the bus.Acomputer’s bus can be expanded to include devices other than those found on the motherboard. The motherboard containsexpansion slots, or openings with multiple electrical contacts, that allow devices such as NICs, modems, or sound cards to connect to the computer’sexpanded bus. The devices are found on a circuit board called anexpansion cardorexpansion board. Inserting an expansion board into an expansion slot establishes an electrical connection between the expansion board and the motherboard. Thus, the device connected to theexpansion board becomes connected to the computer’s main circuit and part of its bus. Withexpansion boards connected to its main circuit, a computer can centrally control the device.Multiple bus types exist, and to become part of a computer’s bus, an expansion board mustuse the same bus type. By far, the most popular expansion board NIC today is one that uses aPCIe bus.PCIe (Peripheral Component Interconnect Express)is a 32-bit bus capable of transferring data at up to 1 Gbps per data path, or lane, in full-duplex transmission. It was introduced in 2004 and has continued to evolve ever since, offering efficient data transfer, supportfor quality of service distinctions, and error reporting and handling. PCIe slots vary dependingon the number of lanes they support: An x1 slot supports a single lane, an x2 slot supportstwo lanes, and so on. Each lane offers a full-duplex throughput of up to 1 Gbps. A PCIe slotcan support up to 32 lanes. Figure 6-1 depicts a PCIe expansion board NIC.You can easily determine the type of bus your PC uses by reading the documentation thatcame with the computer. Someday, however, you may need to replace a NIC on a PCwhose documentation is missing. To verify the type of bus a PC uses, you can look insidethe PC case. (Later in this chapter, you will learn how to open a computer case, check thecomputer’s bus, and install a NIC safely.) If a motherboard supports more than one kind ofexpansion slot, refer to the NIC and PC manufacturers’ guidelines for information on thepreferred type of NIC. If possible, you should choose a NIC that matches the most modernbus on the motherboard. Although you may be able to use the older bus and NIC types
đang được dịch, vui lòng đợi..