Preparing Data

Preparing Data

Data travels on the network in serial form (one bit at a time). Inside the PC, however, data moves along the bus in parallel form (8, 16, or 32 bits at a time). The network adapter card, therefore, must convert the parallel data from the bus into the serial form required for network transmission. If the card receives data from the local system, it can transmit that data to the network. The data then is stored in a memory buffer on the adapter card until the card can catch up.

Because the network adapter card’s software and firmware participate in the Data Link layer of the protocol stack, they are responsible for contributing data-link header information, such as the network adapter card’s physical address (see Chapter 2).

The data bus is a pathway inside your computer that carries data between the hardware components. Four data-bus architectures are used in Intel-based PCs: Industry Standard Architecture (ISA), Extended Industry Standard Architecture (EISA), Micro Channel, and Peripheral Component Interconnect (PCI). In recent models, PCI and EISA are the most common data-bus architectures. ISA is a (more limited) predecessor of EISA. Micro Channel is a data bus developed by IBM for the PS/2 series that never caught on—it is, however, still used for some high-end models.