PC Hardware in a Nutshell, 3rd Edition

Bus Support

A bus is a shared linear pathway that connects multiple devices to provide a communication channel among them. Every bus provides access points to which devices can connect. Any device connected to the bus can communicate bidirectionally with other devices that are connected to that bus. A bus provides access points for three or more devices. A bus that connects only two devices is properly called a port. PC components—processor, cache, RAM, expansion cards, disks, and others—communicate using one or more of the multiple busses that exist in a modern PC. Recent PCs contain several bus types, all of which are coordinated by the chipset, as follows:

Processor bus

Also called the host bus or the Front Side Bus (FSB), the processor bus is used by the processor to communicate with the chipset.

Memory bus

The memory bus connects the memory subsystem to the chipset and thereby to the processor. For most systems and most applications, faster memory bus speed provides only minor performance benefits. Ideally, the speed of the memory bus should match that of the FSB.

Cache bus

Sixth-generation and later processors use a dedicated cache bus (also called the Back Side Bus or BSB) to access the integrated L2 cache. This bus may operate at full processor speed (e.g., Celeron and Coppermine-core Pentium III processors), or at some integer fraction of the processor speed (e.g., Katmai-core Pentium III, K7 and later Athlon processors, and all Pentium 4 processors). Fifth-generation ...