Multimedia devices in computer system that selectively employ a communications protocol by determining the presence of the quaternary interface

摘要

A computer system is presented having various peripheral devices coupled to a PCI local bus (i.e., an expansion bus), a subset of the peripheral devices having quaternary interfaces configured to communicate via quaternary signals conveyed upon the PCI local bus. The various peripheral devices may include a video/graphics card, a sound card, a hard disk drive, a CD-ROM drive, and a network interface card. When data is transferred from a master device to a target device, and the master and target devices both have quaternary interfaces, the master device converts the data to quaternary signals before transmitting the data the target device via the PCI local bus. The target device receives the quaternary signals from the PCI local bus and converts the quaternary signals to the binary data. Two binary digits (i. e., bits) of information are advantageously conveyed using quaternary signals in the time required to transmit a single bit using binary signals, thus providing increased efficiency and reduced bus bandwidth requirements. If either device does not include a quaternary interface, the data is transferred using conventional binary signals. A handshaking protocol may be used to determine if both the master and target devices include a quaternary interface. The handshaking protocol is implemented using handshaking signals conveyed over additional control lines added to the PCI local bus. Alternatively, a configuration memory may be included in the quaternary interface of the master device to reduce the required number of additional control lines from two to one.