typical computer system contains multiple buses. For example, in addition to a
central bus that connects the processor, I/O devices, and memory, some computers have
a special-purpose bus used to access coprocessors. Other computers have multiple
buses for convenience and flexibility — a computer with several standard buses can accommodate
a wider variety of devices.
Interestingly, most computers also contain buses that are internal (i.e., not visible
to the computer’s owner). For example, many processors have one or more internal
buses on the processor chip. A circuit on the chip uses an onboard bus to communicate
with another circuit (e.g., with an onboard cache).