Databusses

Databusses are communication pathways used to transfer data between components in a computer or between devices. They consist of signal lines that carry the data and are usually accompanied by address and control lines as part of a system bus. Data transfers may use parallel wires or high-speed serial links.

The key characteristic of a data bus is its width, measured in bits (for example 8, 16, 32, or 64). The width plus the operating frequency determines the theoretical data rate, i.e., bandwidth. Practical limits come from signal integrity and power.

Data buses can be internal (between processor, cache, memory controller, and memory) or external (to memory modules or peripherals). They may be synchronous, driven by a shared clock, or asynchronous, using handshaking signals. Some buses multiplex address and data on the same wires to save pins.

Architectures differ in topology and access method. Some buses are multi-drop, allowing many devices to listen or speak with arbitration to avoid collisions. Others are point-to-point, such as many modern serial links. Protocols define timing, error checking, and flow control.

Common data-bus standards and concepts include PCI Express (a serial point-to-point bus for expansion cards), USB (a shared serial bus for peripherals), SATA (storage), and internal CPU/memory buses (AMBA AXI or x86 variants). In embedded design, I2C and SPI are widely used as simple data buses.

The term data bus is used with address and control buses to describe the full system bus. Advances in data-bus design aim to reduce latency, increase bandwidth, and balance complexity, cost, and power as systems scale.