A processor bus, also known as the front-side bus, refers to a specific electrical connection within a computer that connects a computer's processor to a chip known as the north bridge. For a computer to properly function, the processor, also known as the central processing unit (CPU), must send out orders and submit pieces of information to the computer’s memory. The processor bus brings messages back and forth between the processor and the north bridge, which in turn sends messages to the computer's memory and other parts of the computer. This allows the computer to perform multiple tasks at once at fast speeds.
The front-side or processor bus is not the only bus found within a computer. The motherboard chipset consists of two main chips, the north bridge and the south bridge. The processor bus transmits messages from the north bridge, also known as the memory controller hub, to the CPU. This area deals primarily with memory and graphics, and messages travel faster on the processor bus. The south bridge deals with processes which do not need to be acted on as quickly as those in the north bridge and sends signals at a slower rate using the PCI bus.
Imagining a motherboard in a computer as a highway and the buses as actual buses carrying passengers is one way to understand computer buses. Each passenger represents an electrical signal that the processor needs to send to the memory to store until it's ready to use it. The data gets on the bus and the bus transports the data to the north bridge, which then sends it on to the memory. When the process needs to use it, the data "rides" the bus back to the processor to wait for further instructions.
Other buses found on the motherboard which help connect parts to the main north and south bridge include the internal bus, the memory bus, and the AGP bus. The internal bus connects the north bridge to the south bridge so they can communicate with each other and other parts of the computer. The memory bus connects the north bridge to the memory. When the CPU needs to save something to the computer's temporary memory, it sends it to the north bridge which passes it on to the computer's memory. The AGP bus, short for accelerated graphics port, works with information relating to graphics display but is becoming less common and is often replaced by an expansion card known as the PCI-E or PCI Express.