A system bus is the shared set of electrical conductors that moves data, addresses, and control signals between a computer’s CPU, memory, and I/O devices.¹

Overview

Classically a bus has three parts: a data bus (the values being moved), an address bus (which memory location or device they go to), and a control bus (timing and read/write signals). The bus width — how many bits cross at once — and its clock set the bandwidth. This shared design comes straight from the von Neumann architecture, where one path connects the processor to a common memory and devices.

Where it fits

Because the components on the motherboard cannot talk directly, the bus is the meeting point, and a shared bus can become a bottleneck when many devices compete for it. Modern systems mostly replace one wide shared bus with many fast point-to-point links — PCIe being the dominant example — but the concept is unchanged: a defined interconnect that lets the parts of a computer exchange data in step.

Sources

1. Bus (computing) — Wikipedia, on data, address, and control buses. ↩

See also

• Central processing unit (CPU)
• Random-access memory (RAM)
• PCI Express (PCIe)
• Motherboard
• Von Neumann architecture
• Input/output (I/O)